Reactions doi: 10.3390/reactions7030038

Authors: Rosario I. Yocupicio-Gaxiola Uriel Caudillo-Flores Andrea Urtaza Ruiz de Esparza Joel Antunez-Garcia Fabian N. Murrieta-Rico Hugo A. Borbon-Nuñez Sergio Fuentes-Moyado Marina G. Shelyapina Vitalii Petranovskii

In this study, lamellar MFI (Mobile Five-membered ring Intergrowth) zeolites pillared with TiO2 were synthesized using tetraethyl orthotitanate (TEOTi) as titanium precursor and evaluated as photocatalysts for Rhodamine B (RhB) degradation under UV irradiation. The materials were characterized by X-ray diffraction (XRD), UV–Vis spectroscopy, N2 adsorption–desorption, photoluminescence spectroscopy (PL), and transmission electron microscopy (TEM). XRD confirmed the preservation of the lamellar MFI structure and the formation of anatase TiO2 pillars within the interlayer space. The composites exhibited hierarchical micro/mesoporosity, high surface areas (>320 m2 g−1), and mesopore sizes of approximately 4.1–4.2 nm. Photocatalytic experiments revealed that the incorporation of TiO2 into the lamellar MFI framework significantly enhanced the degradation kinetics of RhB compared with bare TiO2. The apparent pseudo-first-order rate constants followed the order MFIPTi-6 > MFIPTi-3 > MFIPTi-12 > TiO2 > MFIPTi-24, with MFIPTi-6 exhibiting the highest activity (kapp = 0.049 min−1), approximately 1.6 times higher than that of pure TiO2. Scavenger experiments identified hydroxyl radicals as the predominant reactive species involved in the degradation process. TOC (Total Organic Carbon) measurements showed approximately 80% organic carbon removal, while recyclability tests demonstrated stable photocatalytic performance over six consecutive cycles. These results highlight the potential of lamellar TiO2/MFI composites as efficient and reusable photocatalysts for water treatment applications.

Reactions doi: 10.3390/reactions7030037

Authors: Haidar L. Abdullah Khalid A. Sukkar May Ali Alsaffar

Ozonation is one of the most widely used methods for wastewater treatment. However, it suffers from several drawbacks, including a low reaction rate, long reaction time, and the formation of intermediate byproducts due to incomplete oxidation. Therefore, in this paper, the ozonation process was improved via the MgO nanocatalyst and honeycomb activated carbon (HAC) as a packing material in the bubble column reactor by using the following methods: (O3/MgO, O3/HAC, and O3/MgO/HAC). The results showed that using ozone alone yielded a low chemical oxygen demand (COD) removal efficiency of 63.33% after 90 min, and the phenol concentration was 15 mg/L. However, when the catalyst was added, the efficiency increased to 73.33%, which is attributed to the enhanced generation of more hydroxyl radicals (OH•). The HAC packing material had a positive effect, as the removal efficiency rose to 76.66% due to its effective role in improving the mass transfer inside the reactor. The integrated (O3/MgO/HAC) method proved to be the most effective at achieving a COD removal efficiency of about 83%; furthermore, the efficiency reached 91% when the initial phenol concentration decreased to 10 mg/L. Two doses of catalysts were used, 0.05 and 0.1 g/L, and it was found that the higher dose (0.1 g/L) had the highest efficiency. The effect of the initial phenol concentration and ozone gas flow rate were studied. The study concludes that the use of the MgO nanocatalyst and the honeycomb-structured activated carbon packing material plays an effective role in improving the ozonation process by increasing the reaction rate, reducing treatment time, and decreasing the demand for additional ozone gas supplies, thus achieving significant economic benefits.

Reactions doi: 10.3390/reactions7020036

Authors: Theresa Coetsee Frederik De Bruin Oleg Komarov Artyom Popov Vilena Khudyakova

This study investigates the thermochemical reaction behaviour of scheelite–millscale aluminothermy for direct tungsten alloying in steel production. Experimental mixtures of aluminium, millscale, and scheelite concentrate were simulated using gas–slag–metal (g-s-m) equilibrium calculations in FactSage 8.3 at 2200 °C, and compared with previously reported experimental results. The simulations reproduced metal yields accurately with 0.901 to 0.940 correlation coefficients and predicted tungsten levels consistent with measured steel compositions. However, significant discrepancies were observed in predicted silicon levels, with simulations overestimating steel %Si by up to 3.5%, despite negligible gas-phase losses. Oxygen partial pressure calculations indicate that the Fe/FeO reaction equilibrium controls process reduction conditions. Backcalculation of activity coefficients revealed that FactSage minimisation routines understated silicon activity coefficient values. SiO2 mass transfer may play a role in low %Si in steel, but this is not clear due to differences in expected mass transfer regimes in aluminothermy under ASR and SHS conditions. Overall, the simulations demonstrate adequate predictive capability for alloying trends and metal yields while highlighting limitations in predicting silicon partitioning. These findings confirm the utility of thermochemical simulation for designing aluminothermic feed mixtures, reducing the number of experiments needed to optimise the aluminothermic feed mixture ratios.

Reactions doi: 10.3390/reactions7020035

Authors: Cristian Toncón-Leal Kiara Montiel-Centeno Deicy Barrera Carlos Páez-González Sebastián Amaya-Roncancio Jhonny Villarroel-Rocha Leticia Romero-Castro Karim Sapag

Ordered mesoporous carbons have emerged as versatile supports for Fischer–Tropsch catalysts due to their high surface area, tunable pore architectures, and chemical stability. However, the influence of active-metal identity on product selectivity within a common carbon framework remains insufficiently understood, particularly when Fe and Co are compared under rigorously identical conditions. To address this aspect, we prepared Fe- and Co-based catalysts with comparable nominal metal loadings supported on CMK-5 carbon material and evaluated their structural, surface, and catalytic properties. Comprehensive characterization revealed distinct metal-dependent behaviors, and catalytic testing between 423 and 598 K at 2 MPa showed that the catalyst CMK-5(Co10) exhibited substantially higher activity, whereas CMK-5(Fe10) provided a more stable product distribution and exclusively paraffinic C2–C3 products across the studied temperature range. In contrast, CMK-5(Co10) displayed a pronounced temperature-dependent selectivity, with increasing methane formation and the emergence of olefinic C2–C3 species at intermediate and high temperatures. Chain-growth probabilities were consistent with these trends. Complementary Density Functional Theory and Kinetic Monte Carlo analyses indicated stronger binding of carbonaceous intermediates on Fe clusters and more accessible C–C coupling pathways on Co clusters. Together, these results clarify how active-metal identity governs selectivity within a shared CMK-5 architecture and provide guidelines for designing carbon-supported Fischer–Tropsch catalysts with controlled product distributions.

Reactions doi: 10.3390/reactions7020034

Authors: Karen Castellanos-Espitia Alver Castillo-Aguirre Mauricio Maldonado-Villamil

In the present article, tetra(nonyl)calix[4]resorcinarene, tetra(p-methoxyphenyl)calix[4]resorcinarene, and tetra(p-bromophenyl)calix[4]resorcinarene were synthesized by the cyclocondensation method in acid medium. In the case of tetra(nonyl)calix[4]resorcinarene, only the crown conformer was obtained, while in the case of tetra(p-methoxyphenyl)calix[4]resorcinarene and tetra(p-bromophenyl)calix[4]resorcinarene, a conformational mixture (crown and chair) was formed, separated, and purified via the recrystallization technique. Subsequently, the per-O-acetylation reaction of the pure conformers was carried out. According to the RP-HPLC and 1H-NMR results, the per-acetylation product of the crown conformer of tetra(nonyl)calix[4]resorcinarene retained its conformation, likewise the per-O-acetylation products of the chair conformer of tetra(p-methoxyphenyl)calix[4]resorcinarene and tetra(p-bromophenyl)calix[4]resorcinarene. On the other hand, the per-O-acetylation product of crown conformers of tetra(p-methoxyphenyl)calix[4]resorcinarene and tetra(p-bromophenyl)calix[4]resorcinarene gave rise to the formation of the boat conformer.

Reactions doi: 10.3390/reactions7020033

Authors: Filip Brleković Nikolina Miočić Katarina Mužina Stanislav Kurajica

This study investigates the mechanochemical synthesis of silver molybdate (Ag2MoO4). Three silver precursors (AgCl, AgNO3, Ag2SO4) in combination with sodium molybdate dihydrate as the molybdenum precursor were used. Three corresponding sodium salts, which are also formed as byproducts, were employed as process control agents (PCAs) to investigate the possibility of obtaining fine-grained silver molybdate. Milling was performed in a planetary mill at 600 and 100 rpm, and for 2 h, 15 min, and 5 min. X-ray diffraction analysis (XRD) revealed that AgCl is completely unreactive in this type of reaction, whereas AgNO3 and Ag2SO4 form crystalline Ag2MoO4. Additional sample characterization included Fourier transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and simultaneous differential thermal and thermogravimetric analysis (DTA-TGA). The results indicate that the silver molybdate formation reaction is favorable and rapid. Even under the mildest conditions, including the presence of PCA, micron-sized silver molybdate particles were obtained. A greater rotation rate and longer milling time resulted in a decrease in particle size, but also an increase in sodium content. However, unlike the few existing reports on the mechanochemical synthesis of Ag2MoO4, which, despite harsh milling conditions, did not yield a phase-pure product, our approach produced well-crystallized and pure silver molybdate even under the mildest synthesis conditions.

Reactions doi: 10.3390/reactions7020032

Authors: Ntampaka D. Clarisse Dong Li Ze-Ya Zhang Yi-Han Tang Qun Chen Zhi-Hui Zhang

In this study, a novel magnetic metal–organic framework (MOF) composite, Pd@UiO-66@Fe3O4, was successfully synthesized as a high-performance heterogeneous catalyst for the Suzuki–Miyaura cross-coupling reaction. The material was prepared by loading nano-sized carboxylated Fe3O4 onto UiO-66 via an in situ solvothermal method, followed by the encapsulation of Pd nanoparticles using an ultrasound-assisted dual-solvent method (DSA). Characterization results, including PXRD and TEM, confirmed that the ternary composite retains the structural integrity of UiO-66 while incorporating magnetic functionality and well-dispersed Pd active sites. The catalyst exhibited high catalytic performance for the coupling of aryl iodides and aryl boronic acids. Furthermore, the catalyst demonstrated good compatibility with the substrates examined and excellent stability. Due to the integration of carboxylated Fe3O4, the composite could be easily separated from the reaction mixture using an external magnet and reused for at least five cycles without a significant loss in catalytic activity. The high activity and durability are attributed to the integrated roles of the Pd nanoparticles, the porous MOF support, and the magnetic Fe3O4 component, which respectively provide catalytic active sites, structural stabilization/dispersion, and magnetic recoverability.

Reactions doi: 10.3390/reactions7020031

Authors: Yuan-Gee Lee Yi-Hui Li I-Chen Hsiao Chung-Kwei Lin Yuh-Jing Chiou Pei-Jung Chang Yu-Ching Weng

An optimum In0.2Cd0.8S composition was synthesized with graphene to enhance photocatalytic performance. Graphene incorporation altered the morphology from compact grains to a loosely aggregated structure without affecting the crystal phase, as confirmed by XRD. XPS analysis indicated surface-level interaction between graphene and the In–Cd–S matrix, rather than lattice integration. Mott–Schottky and Kubelka–Munk analyses revealed n-type semiconducting behavior and a slight band gap increase from 2.46 to 2.51 eV upon graphene blending. UV–Vis and IPCE measurements showed enhanced light absorption, with IPCE values of 9.33% and 5.01% at 380 nm and 480 nm, respectively. The 3.85 wt% graphene-modified photocatalyst achieved a hydrogen evolution rate of 4.97 μmolh−1cm−2, more than triple that of pristine In0.2Cd0.8S. These enhancements are attributed to improved charge transport and interfacial activity provided by the graphene.

Reactions doi: 10.3390/reactions7020030

Authors: Yoshio Nosaka

In this review, some special characteristics of the reactions in semiconductor photocatalysis are presented. At first, since a pair of the redox reactions take place at the same particle, a particle-based kinetic method was presented and applied for the Langmuir–Hinshelwood kinetics to describe the photocatalytic oxidation as a function of both the reactant concentration and the light intensity. Since the surface electron transfer (ET) reactions are the subject of electrochemistry, the difference in the characteristics from particulate semiconductor photocatalysis was pointed out by showing each electric potential near the solid surface. Different from ET in electrochemistry, the ET frequency is limited by the photon absorption in photocatalysis. In the estimation of the reaction rate, the validity of Marcus theory in photocatalysis was argued. Almost all photocatalytic reactions are irreversible, because, before the charge recombination, the oxidation and/or reduction must take place at the same particle. Then, the kinetics for irreversible reaction was discussed. As an exception, the reversible reduction reaction of methylviologen with a hole scavenger was presented. By changing pH, the energy levels of thermalized electrons in TiO2 particles were estimated, and the difference of the flat band potentials between anatase and rutile was clearly explained. Thus, various uniqueness of photocatalytic reactions in aqueous suspension of semiconductor particles were demonstrated.

Reactions doi: 10.3390/reactions7020029

Authors: Wenping Ma Jia Yang Gary Jacobs Robert B. Pace Dali Qian

Addition of an Author [...]

Reactions doi: 10.3390/reactions7020028

Authors: Diego Diaz Dana Arias Jorge Noé Díaz de León Ana Belén Dongil Laura Martínez-Quintana Néstor Escalona Gina Pecchi Carla Herrera Catherine Sepulveda

Pure LaFeO3@C and LaCoO3@C and substituted LaFe1-xCoxO3 and LaCo1-xFexO3 perovskites (x = 0.10; 0.30) were used as catalysts for the liquid-phase oxidation of furfural at 150 °C and 30 bar of O2 pressure. The perovskites were characterized by XRD, H2-TPR, N2 physisorption, TPR-MeOH, and XPS. The carbon in situ incorporation (@C) increases the surface area, favoring oxygen mobility leading to LaFeO3@C stabilizing the redox pair Fe3+/Fe2+. In contrast, no evidence of the formation of a LaCoO3@C perovskite structure through @C incorporation was observed. The gradual substitution of Fe with Co (10 and 30%) in LaFeO3@C decreases the crystallinity, redox and basic properties, and surface area. For LaCoO3@C, after the substitution of Co with 10 and 30% of Fe, only metal (La, Fe, Co) oxides as segregated phases were observed. The highest catalytic activity and selectivity to maleic acid of LaFeO3@C is attributed to the higher surface area, crystalline structure, and surface-reducible Fe3+ species, favoring oxygen mobility and promoting their more oxidizing capacity. The lower catalytic activity of LaCoO3@C, the Co- and Fe-substituted LaFeO3@C and LaCoO3@C catalysts, is attributed to the smaller surface area, and the similar selectivity towards maleic acid, 5-hydroxy-2(5H) and furanone indicates that the active site type is not modified in comparison to LaFeO3@C.

Reactions doi: 10.3390/reactions7020027

Authors: Collin B. Dean Amelia B. Jones Olivia N. Silvers Ava J. Travis Bayla L. Zohbe Gary W. Breton

N-Alkyl urazoles are important heterocyclic compounds that serve as important precursors to potent N-alkyl 1,2,4-triazoline-3,5-dione electrophiles. Traditional methods for urazole synthesis rely upon the use of toxic isocyanates. We have modified and optimized an overlooked and poorly described method from the literature for the synthesis of urazoles that now avoids the use of isocyanates, limits the use of solvents, and provides urazoles without the need for purification steps. A variety of urazoles are afforded in good to high yields.

Reactions doi: 10.3390/reactions7020026

Authors: Yuki Maeda Yoshimitsu Hashimoto Yuriko Oshita Sayuri Yuhara Osamu Tamura Nobuyoshi Morita

The 1,3-dipolar cycloaddition of nitrones with hydrazones affords 5-iminoisoxazolidines as the major products, in contrast to the reaction with enals, which exclusively afford 4-acylisoxazolidines. This reversal of regioselectivity can be explained in terms of frontier orbital theory. The 5-iminoisoxazolidines are easily converted to 5-acylisoxazolidines.

Reactions doi: 10.3390/reactions7020025

Authors: Xujie Zhang Wanqiang Xu Hehuan Peng

A series of bifunctional hierarchical HZSM-5 catalysts modified with Zn, Ga, Ni, Cr, or Ag were synthesized via impregnation, and their performance in the catalytic fast pyrolysis of walnut shells was systematically evaluated. The influence of the metal species and concentration of NaOH used for desilication (0.20–0.40 mol·L−1) on the yield of light aromatics was assessed. Ga/HZSM-5 and Zn/HZSM-5 exhibited the most pronounced enhancement at 0.35 mol·L−1, significantly outperforming the unmodified HZSM-5. Building on this finding, Zn-Ga bimetallic hierarchical catalysts were developed, and the effect of the Zn:Ga loading ratio (1%:2%, 1.5%:1.5%, 2%:1%) was investigated. The 1%Zn/2%Ga catalyst delivered the highest performance, achieving a total aromatic yield of 3.876 × 104 a.u.·mg−1, with 82% BTX (benzene, toluene, and xylenes) selectivity. The term “a.u.” stands for “arbitrary units,” typically derived from peak area counts obtained through GC-MS analysis. These values represent the relative signal intensity detected by the instrument, rather than absolute quantities of the substance. To more accurately characterize the aromatic hydrocarbon yield, these data are normalized to the yield of aromatic hydrocarbons per unit mass. These findings demonstrate that the combination of Zn-Ga modification and tailored mesoporosity can markedly enhance the production of high-value benzene, toluene, and xylene (BTX) aromatics from lignocellulosic biomass.

Reactions doi: 10.3390/reactions7020024

Authors: Lucas Alves da Silva Egydio Terziotti Neto Éder Valdir de Oliveira Antônio Matheus Lima Bezerra Rodrigo Brackmann Rita Maria Brito Alves

Interest in further developments of the classical Fischer–Tropsch technology has increased in recent years. The development of processes capable of producing synthetic fuels has become a highly attractive research area due to the continuous global growth in energy demand. An extensive review covering the full development chain (from laboratory-scale experiments to pilot-scale studies and plant-level implementations) is therefore of significant relevance. Consequently, this review aims to be a reference by integrating findings across different development levels of Fischer–Tropsch synthesis technologies, thereby enabling a holistic perspective of the pathway toward industrial-scale deployment. The present work thus critically reviews recent advances in catalyst development, including the role of active phases, particle size effects, supports, and promoters, as well as the growing contribution of in situ and operando characterization techniques. In parallel, progress in kinetic and mechanistic modeling is discussed, highlighting both classical approaches and emerging data-driven and optimization-based methods. Different reactor technologies, from classical to novel technologies, are also analyzed with respect to hydrodynamics, heat and mass transfer limitations, and reactor intensification strategies. At the process level, the review assesses integrated and intensified Fischer–Tropsch-based routes, with particular emphasis on CO2 utilization pathways, process integration, polygeneration schemes, and optimization frameworks. The potential of artificial intelligence and machine learning tools to accelerate catalyst discovery, reactor optimization, and process design is also addressed. Overall, this review identifies key technological advances, remaining challenges, and research gaps that must be addressed to enable economically viable and environmentally sustainable, and scalable Fischer–Tropsch processes to meet future energy demands.

Reactions doi: 10.3390/reactions7020023

Authors: Félix Monteiro Pereira Samuel Conceição Oliveira

This study presents a transient mathematical model and its numerical solution for the moving-boundary problem related to substrate diffusion and reaction in enzymatic catalytic particles. The main focus is on bioreactor startup, where the initial substrate concentration inside the particles is zero, forming a dead core that shrinks over time and makes the catalytic effectiveness factor time-dependent. The substrate mass balance leads to a partial differential equation with a moving boundary, solved using the method of lines coupled with Newton’s method (MLN), implemented in Wolfram Mathematica (WM). The proposed approach was validated for zero- and first-order kinetics at steady state, whose analytical solutions are available. Compared to the method of orthogonal collocation on finite elements, the MLN offers advantages such as not requiring an initial concentration profile and simple implementation in WM. The results demonstrate that the proposed method provides accurate and physically consistent solutions, contributing to a better understanding of dead-core dynamics and supporting the design of heterogeneous bioreactors with immobilized enzymes.

Reactions doi: 10.3390/reactions7020022

Authors: Jhonathan Castillo-Saenz Eduardo Estrada-Movilla Benjamín Valdez-Salas Ernesto Beltrán-Partida Jorge Salvador-Carlos Esneyder Puello-Polo Roberto Gamboa-Becerra

Red Amaranth (RA) Azo dye is a persistent pollutant in wastewater and stands as a toxicological risk, which has led to the development of effective methods for its removal and photocatalytic degradation. Therefore, CeO2 nanoparticles were synthesized by a controlled precipitation method, and Ultraviolet-Visible (UV–Vis) analysis and Tauc plots yielded a band gap of ~3.24 eV. The CeO2 nanoparticles showed the fluorite cubic phase, and nearly spherical particles with an average size of ~10 nm. Nitrogen physisorption revealed a type IV isotherm with a Brunauer–Emmett–Teller (BET) surface area of 85.27 m2·g−1 and a total pore volume of 0.27 cm3·g−1, indicating a mesoporous structure and high surface accessibility. The chemical behavior showed Ce and O, consistent with phase purity. Photocatalytic performance was evaluated in 20 ppm aqueous solution of RA under 365 nm UV irradiation (LED 100 W), with a temperature of ~20 °C and a 15 min dark adsorption step. Concentration decay was followed at λmax = 520 nm by Lambert–Beer. The degradation efficiency η and pseudo-first-order kinetic were obtained from ln(C0/Ct) vs. time. In addition, chemical oxygen demand (COD) tests were performed on RA solution before and after photodegradation, showing a COD reduction of ~85% (from 19.8 to 3 mg O2·L−1), which corroborates mineralization beyond chromophore bleaching. Under [C0 = 20 mg·L−1] and [mcat = 1.0 g·L−1], CeO2 achieved [RA = 90% at 180 min, k = 0.0125 min−1]. These results demonstrate that CeO2 is an effective photocatalyst for RA degradation under UV-A irradiation, integrating adsorption, kinetic behavior, and mineralization performance into a coherent structure–property relationship.

Reactions doi: 10.3390/reactions7010021

Authors: Jose L. Buitrago Leticia Jésica Méndez Mónica Laura Casella Juan Antonio Cecilia Enrique Rodríguez-Castellón Ileana D. Lick Luis R. Pizzio

This work presents the synthesis, characterization, and application of zirconium oxide (ZrO2)-based catalysts, modified with macro (silica nanospheres, NSP-SiO2) and mesopore templates (Pluronic 123), impregnated with tungstophosphoric acid (TPA), in the catalytic pyrolysis of tomato agro-industrial residues. The NSP-SiO2 (SXX) and P123 (PYY) amount mainly influences the ZrO2SXXPYY-specific surface area (SBET) and average pore diameter (Dp). 31P MAS NMR and FT-IR characterization results show that TPA (H3PW12O40) was partially transformed into [P2W21O71]6− and [PW11O39]7− during the synthesis steps. The acidic properties of ZrO2SXXPYY samples containing 25 and 50 wt% of TPA (ZrO2SXXPYYT25 and ZrO2SXXPYYT50, respectively) are dependent on both the TPA content and the support nature. Bio-oil composition and product selectivity were strongly influenced by the textural and acid-based properties of the catalysts. Notably, non-catalytic pyrolysis favored pathways leading to C2 compounds, with a high content of acetic acid and hydroxyacetone. In contrast, the use of catalysts promoted the formation of higher molecular weight oxygenated compounds (C5–C6), specifically furans, aldehydes, and ketones.

Reactions doi: 10.3390/reactions7010020

Authors: Alhumam A. Al-Shammari Bashir Y. Al-Zaidi Ali Al-Shathr

Linear alkylbenzene (LAB) is the main raw material used to make biodegradable detergents, and its production process is based on aromatic alkylation. HY zeolites that have undergone controlled dealumination and desilication have led industrial standards amongst solid acid catalysts because of their controllable acidity and hierarchical pore structure. Coke formation in such systems can assume a dual role, which is dependent on its condition. Though the over-deposition is known to cause deactivation by blocking the micropores, Bronsted acid-site masking, and diffusion collapse, the low-level deposition could also be done to increase the monoalkylate selectivity by the pore mouth catalysis, steric modulation, and selective suppression of secondary alkylation pathways. The critical review is done on the structural-kinetic interaction that determines the coke evolution in HY-based catalysts. In order to moderate the acid-site density and enhance hydrothermal stability, dealumination (Si/Al optimization of about 2.5 to 30–100) occurs, but to reduce deep-pore coke formation, desilication (interconnected mesopores) is created. The bimodal porosity and regulated acidity are found to be synergistic, as hierarchical HY zeolites produced through successive cycles of steam and alkaline treatments not only show LAB selectivity in excess of 90% but also exhibit much longer catalyst lifetimes. Quantitative research on the beneficial coke regime revealed that it was composed of about 36 wt% hydrogen-rich species, which were localized at the pore mouths, hence enhancing monoalkylation selectivity by 15–40%. Beyond a critical transition window (e.g., 8–12 wt.%), coke formation to condensed polyaromatic and graphitic products leads to fast deactivated coke formation, which is due to percolation limits and transport-controlled kinetics. More advanced techniques of characterization of the coke, e.g., temperature-programmed oxidation (TPO), 27Al MAAS NMR, and UV-Raman spectroscopy, indicate how the coke is changed to highly structured graphitic deposits of high oxidation activation energy. Activity recovery of 85–98% is obtained in regeneration processes, including controlled oxidative calcination, microwave-based and plasma-based processes, and thermal management protocols, and it would be determined by the chemistry of the coke, its spatial distribution, and the regeneration protocols. This paper has developed a mechanistic coke control system by cross-tuning the acidity and development of an effective pore network, which led to a sustainable aromatic alkylation reaction with minimal activity loss, high selectivity, and long life.

Reactions doi: 10.3390/reactions7010019

Authors: Amira Mahfoudhi Nidhal Tarhouni Othman A. Alghamdi Ahmed Fendri Adel Sayari

Rhizopus oryzae lipase (ROL) is a key enzyme involved in olive oil spoilage and acts as a virulence factor in fungal infections. Natural lipophilic lipase inhibitors are crucial for mitigating economic losses resulting from lipid degradation in stored or decaying olive fruits. This study evaluated a series of enzymatically synthesized piperate esters with varying alkyl chain lengths (butyryl, C4; octyl, C8; dodecyl, C12) for their inhibitory effects on ROL activity. Octyl piperate (C8) demonstrated the highest potency, with IC50 values of 0.05 mg/mL using methods B and C or 0.25 mg/mL using method A. Molecular docking indicated that C8 achieved the most favorable predicted binding energy (Gscore: –11.134 kcal/mol), primarily through hydrophobic interactions (Val329, Ala212, Phe209) and hydrogen bonds with oxyanion hole residues (Ser268, Thr206, Gln241). Molecular dynamics simulations confirmed that C8 maintained stable binding and stabilized the catalytic residues. In comparison, C4 exhibited weaker interactions, and the longer C12 chain induced conformational instability and steric hindrance. These results establish a parabolic structure–activity relationship, identifying the octyl chain (C8) as optimal for ROL inhibition among the tested derivatives. The rational design of lipophilic, biodegradable lipase inhibitors thus positions octyl piperate as a promising candidate for extending olive storage and shelf life, and as a scaffold for developing natural antifungal agents targeting virulent R. oryzae strains.

Reactions doi: 10.3390/reactions7010018

Authors: Luz Clara Andia-Marron Jessica Abad-Salcca Juan Taumaturgo Medina-Collana Edgar Williams Villanueva-Martinez Jorge Amador López-Herrera Richard Brandon Guevara-Salcedo Leonard Ordoñez-Santa Maria Rodolfo Paz-Salazar Fredy Andrés Taipe-Castro Jorge Alberto Montaño-Pisfil Segundo Alberto Vásquez-Llanos

Hydrodynamic cavitation (HC) is an efficient technique for biodiesel production. The main contribution of this study is the development of a modular reactor with a universal stainless steel joint, whose design facilitates the installation, replacement, and maintenance of the orifice plate by eliminating flanges and bolts during assembly. Using this reactor, the study evaluated the synergistic interaction between feed pressure and methanol:oil molar ratio in the transesterification of soybean oil, employing a 32 factorial design. The orifice plate was 3 mm thick and had 19 holes with a diameter of 1.0 mm, installed downstream of the pump. The process was carried out for 45 min, using NaOH at 1 wt% relative to the oil and at 60 ± 5 °C. Feed pressures of 1.72, 2.41, and 3.10 bar and methanol:oil molar ratios of 6:1, 8:1, and 10:1 were evaluated, reaching a maximum yield of 92.98% at 3.10 bar and 8:1. Analysis of variance (ANOVA) confirmed a significant interaction (p < 0.0001) and allowed a second-order polynomial model to be fitted (R2 = 0.9981). In contrast, conventional mechanical agitation required 90 min to achieve 95% yield. The biodiesel produced met most American Society for Testing and Materials (ASTM) D6751 requirements, confirming the potential of HC as a viable alternative for intensifying biodiesel production.

Reactions doi: 10.3390/reactions7010017

Authors: László Kiss Heng Li Xiao-Hang Chen Sándor Kunsági-Máté

Ethanol is widely used as an additive in fuels, so its effect on the electrochemical oxidation of triethanolamine was investigated on a 25 μm platinum microelectrode. Ethyl acetate was applied as a cosolvent to increase the permittivity of the medium. A hydrocarbon n-heptane, typically present in gasohol samples as the main component, was studied, and its solutions prepared with ethanol in the entire concentration range (between 0 and 100 v/v% ethanol contents) were mixed with ethyl acetate. The as-prepared liquid mixtures were prepared separately, and they were mixed with ethyl acetate in uniform ratios. Triethanolamine, the selected redox-active compound, exhibited a sharp peak in ethyl acetate at the 15 mM concentration. The changes in the voltammograms served as a good template for quantitative analysis of ethanol content. The most suitable analytical signal used for it was the current minimum after the anodic peak, and this parameter proved more sensitive and reproducible than the anodic peak height itself. The scatterings of the current minimum values were typically within some nanoamperes. MTBE (methyl tert-butyl ether) was added to the apolar mixtures of ethanol, and this ether had a negligible interfering effect on the estimation of ethanol content.

Reactions doi: 10.3390/reactions7010016

Authors: Hassan Shoyiga Msimelelo Siswana

Magnesium-sulfur (Mg-S) batteries present a compelling energy storage solution, characterised by their remarkable theoretical energy density and economic viability. Nonetheless, challenges arise, including swift capacity degradation and suboptimal polysulfide (acting as an electronic and ionic insulator) utilisation, mainly due to a phenomenon known as the polysulfide “shuttle effect.” This effect also leads to a decline in battery performance. The Becke, 3-parameter, Lee-Yang-Parr (B3LYP) functional and 6-311G (d,p) basis set were used to examine the optoelectronic and charge-transfer properties of a polyaniline-pyrrole (PANIPyr) composite, emphasising interatomic and electronic interactions that enhance charge transport and oxidation of MgS2. The findings demonstrate the presence of coordination bonding between hydrogen in pyrrole and the N− ion in quinonediimine of polyaniline, significantly enhancing the electrical properties of PANI. The PANIPyr_P1 (P1-pyrrole attached at position one) configuration exhibits the lowest Ɛgap and the highest charge-transfer capacity, compared to other studied molecules in this work, thereby improving reactivity towards polysulfides in comparison to pure PANI. Significant electrical interactions at this site establish accessible electrophilic and nucleophilic regions that stabilise the ionic sides of the polysulfides, thus reducing the shuttle effect and improving charge transport at the interface. PANIPyr_P1 demonstrates viability for minimising polysulfide migration and enhancing cathodic efficiency in Mg-S batteries, thereby laying a foundation for future investigations into polymer-based cathode modifiers.

Reactions doi: 10.3390/reactions7010015

Authors: Karlo I. Martinez-Soto Mara Beltrán-Gastélum Noé Arjona Sergio Pérez-Sicairos Samgopiraj Velraj Jiahong Zhu Moises I. Salazar-Gastélum

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are two processes that occur during the operation of the cathodic electrode in Zn–Air batteries, which enable the integration of alternative energy sources into electrical energy distribution systems. Transition metal oxides, such as perovskites based on LaNiO3, are promising electrocatalysts for the ORR and OER in alkaline medium due to their versatile structure, allowing for the substitution of certain atoms with dopants, which enhances the catalytic activity for both reactions. This work reports an electrochemical study of the catalytic activity toward ORR and OER of perovskite catalysts (LaNiO3 doped with transition metals (Fe, Mn, or Pd)) in the presence of carbon-based materials as supports (multiwalled carbon nanotubes (MWCNT), graphene oxide nanosheets (GO), and graphitic carbon (C)). The results revealed interesting catalytic properties in both reactions, particularly La(Ni0.9Pd0.1)O3/MWCNT, which showed an ORR activation potential of 0.87 V vs. RHE, comparable to that of the commercial Pt/C catalyst (0.99 V vs. RHE), while the overpotential for OER was lower than that of the Pt/C catalyst (1.68 V vs. RHE for La(Ni0.9Pd0.1)O3/MWCNT and 1.79 V vs. RHE for the commercial Pt/C).

Reactions doi: 10.3390/reactions7010014

Authors: Petar Štrbac Davor Margetić Anamarija Briš

Guanidines are structurally unique, highly basic, nitrogen-containing organic compounds with strong hydrogen-bonding ability and biological activity, providing valuable functionality in medicinal chemistry, organocatalysis, and materials science. Among modern strategies for assembling guanidine-containing molecules, cycloaddition reactions have emerged as powerful tools due to their efficiency, stereoselectivity, and ability to rapidly build molecular complexity. Recent innovations have expanded cycloaddition methodologies for generating guanidine functionalities, incorporating guanidine-containing substrates, and using guanidine-based catalysts. This review summarizes these advances and highlights the current trends in guanidine-related cycloaddition chemistry.

Reactions doi: 10.3390/reactions7010013

Authors: Zanele P. Vundla Holger B. Friedrich

This study systematically investigates the role of Ni in Co2SiO4 in a bimetallic (Co2+,Ni2+)2SiO4 olivine-type system and the materials’ catalytic efficiency in a model Heck–Mizoroki coupling reaction. Thus, a series of olivines with varying (Co2+,Ni2+)2SiO4 compositions (0–100% Ni) was synthesised and characterised by ICP-OES, FTIR/Raman, P-XRD and XPS analysis. Ideal mixing of metals was achieved with (49:51) Co:Ni. Catalytic testing revealed distinct conversion vs. time profiles, with the (69:31) Co:Ni olivine exhibiting the best overall performance, combining good reactivity with near-perfect selectivity (>99%) and improved stability. Mechanistic pathways were probed through product scope analysis, reactant–product temporal profiling, leaching and radical scavenging experiments. Results suggest a radical-assisted Heck–Mizoroki mechanism. Spectroscopic data correlated Co2+ and Ni2+ incorporation with M1 and M2 site occupancy, where Ni2+ M2 sites enhanced reactant activation and intermediate stability and Co2+ in the M1 site enhanced product release, though also homocoupling in Co2SiO4. Minimal leaching was observed for all bimetallic catalysts. These findings highlight the tunability of bimetallic olivines for C–C coupling reactions via controlled cation distribution.

Reactions doi: 10.3390/reactions7010012

Authors: Amarendra Nath Maity Amiya Kumar Medda Shyue-Chu Ke

The cycloaddition reaction is one of the most common reactions in organic chemistry. It has been applied in various fields. Herein, we focus on the application of cycloaddition reactions in investigating biological molecules and materials using magnetic resonance techniques. To facilitate magnetic resonance studies such as electron paramagnetic resonance (EPR) spectroscopy and paramagnetic nuclear magnetic resonance (NMR) spectroscopy, there is often a requirement to attach spin labels and paramagnetic tags to the system of interest. The cycloaddition reaction is one of the ways to tether these spin labels and paramagnetic tags. In this review, we highlight the applications of various cycloaddition reactions such as the Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction, the strain-promoted azide–alkyne cycloaddition (SPAAC) reaction and the Diels–Alder reaction in the interdisciplinary field of magnetic resonance studies of biomolecules, including proteins, nucleic acids, carbohydrates, lipids and glycans, as well as materials.

Reactions doi: 10.3390/reactions7010011

Authors: Ulf Prüße Laslo Eidt Anja Kuenz

Fumaric acid is one of the most important bio-based chemicals, with applications in the food, feed, polymer, pulp, and pharmaceutical industries. To overcome the limitations of the current petrochemical production process, alternative methods are being developed. Biotechnological production using wild-type fungi like Rhizopus sp. is a promising alternative. In this study, apple pomace was used as a carbohydrate source for fumaric acid production using Rhizopus arrhizus NRRL 1526. Our focus was on the use of free, non-structurally bound carbohydrates present in high amounts in apple pomace originating from direct apple juice processing. Three processes were compared: pressing, extraction, and a combination of both. Two cultivation strategies were applied: pre-culture and separate upstream biomass production. Using the pre-culture approach, a fumaric acid titer of 68.3 g/L was achieved with a yield of 0.53 g/g and a productivity of 0.29 g/(L·h) from synthetic apple pomace juice. Separate biomass production enabled growth-decoupled fumaric acid production, yielding 50.2 g/L and 79.3 g/L with yields of 0.82 g/g and 0.54 g/g and productivities of 0.17 g/(L·h) and 0.27 g/(L·h) from synthetic and real apple pomace juice, respectively. Thus, the efficient use of apple pomace for the fermentative production of fumaric acid is shown.

Reactions doi: 10.3390/reactions7010010

Authors: Guoqing Zhang Peng Zhang

Exploring effective oxygen reduction reaction (ORR) electrocatalysts is essential for advancing solid-state alkaline zinc–air batteries (ZABs). This paper presents the synthesis of silver–manganese dioxide–carbon nanotubes (SMC) ternary composites as an electrocatalyst for air electrodes, achieved through one-step pyrolysis of silver permanganate under microwave irradiation. Characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersion spectrometer (EDS) consistently confirmed the composition of SMC, comprising silver and alpha-manganese dioxide anchored on the surface of carbon nanotubes (CNTs). Electrochemical tests including polarization and chronoamperometry curves demonstrated the superior electrocatalytic activity of SMC for ORR compared to chemically produced electrocatalysts in alkaline conditions. Furthermore, the performance of a solid-state zinc–air cell with SMC as the electrocatalyst was evaluated, showing a long discharge voltage plateau and a capacity of 60.03 mAh at 30 mA·cm−2. The study also delves into the mechanism behind the enhanced electrocatalytic activity, concluding that the strategy and electrocatalyst developed in this research offer a promising approach for creating efficient oxygen reduction catalysts for solid-state zinc–air batteries.

Reactions doi: 10.3390/reactions7010009

Authors: Jingyang Wu Jinniu Miao Yue Wang Liqian Zhao Jiaji Liang Peng Du

The stability of perovskite materials in humid conditions significantly hinders their practical deployment. This study employed ab initio molecular dynamics (AIMD) simulations based on the Car–Parrinello approach to elucidate the adsorption mechanisms within two systems: CH3NH3PbI3-15O2-2H2O and CH3NH3PbI3-15O2-5H2O. The findings indicate that in the system with a higher water content (5H2O), the degradation of the perovskite skeleton is more severe. Additionally, the adsorption energy of oxygen molecules significantly increases, along with more pronounced charge transfer between the oxygen and the perovskite material. The study also reveals that although water molecules contribute to the damage of the perovskite skeleton, oxygen molecules are the primary culprits. These insights not only clarify the specific impacts of various components in a mixed-gas environment on perovskite stability but also provide an essential theoretical basis for future modifications and optimizations of perovskite materials.

Reactions doi: 10.3390/reactions7010008

Authors: Mirosław Krzysztof Szukiewicz Erwin Górka Elżbieta Chmiel-Szukiewicz

In this study, the response surface method (RSM) was used to determine the best reaction conditions for the gas-phase hydrogenation of carbon dioxide on a commercial nickel-based catalyst. The RSM was applied in our previous study to find the optimal conditions for the same process carried out in laboratory-scale tubular reactors. The main benefits observed were fast detection of optimal conditions and the high precision of the optimum detected (which was experimentally confirmed). These advantages were due to the small number of experiments conducted and the simplicity of the models employed; only linear and quadratic models were developed. The successful result encouraged us to carry out experiments in a larger-scale reactor—an intermediate between a laboratory plant and a pilot plant. This approach helped us to fix some problems resulting from the larger scale of the process conducted. Despite the difficulties described in the main part of this article, we can recommend using the RSM as a tool for supporting experimentation and substantially speeding up the analysis of results and their introduction into practice. At the process scale considered, maximum carbon dioxide conversion was obtained at a temperature of 354 °C and a ratio of molar fluxes of H2 to CO2 equal to 3.9. It should be emphasized that this result was confirmed experimentally.

Reactions doi: 10.3390/reactions7010007

Authors: Sari Rautiainen Tyko Viertiö Niko Vuorio Felix Hyppönen Luděk Meca Pavel Kukula Juha Lehtonen

Black liquor, the side stream from Kraft pulping, is a promising feedstock for the production of renewable fuels via hydrothermal liquefaction (HTL). However, further upgrading of the black liquor HTL oil is required to reduce the oxygen content for fuel use. In this work, the hydrodeoxygenation (HDO) of black liquor HTL oil model compounds was investigated to enhance the understanding of catalyst activity and selectivity under hydrothermal conditions. The study focused on isoeugenol and 4-methylcatechol as model compounds, representing different functionalities in black liquor-derived HTL-oil. Sulfided NiMo catalysts supported on titania, zirconia, activated carbon, and α-alumina were evaluated in batch mode at subcritical and supercritical upgrading using hydrogen gas. The results show that isoeugenol was fully converted in all experiments, while 4-methylcatechol conversion varied depending on the catalyst and reaction conditions. Phenols were obtained as the main products and the maximum degree of deoxygenation achieved was around 40%. This research provides insights into the potential of hydrothermal HDO for upgrading BL-derived biocrudes, emphasising the importance of catalyst selection and reaction conditions in hydrothermal conditions.

Reactions doi: 10.3390/reactions7010006

Authors: Hélène Pellissier

The Sakurai reaction constitutes a valuable tool for carbon–carbon bond formation. The use of nontoxic allylic reagents as well as the atom economy of the global process has prompted the development of enantioselective (aza)-variants based on the use of chiral organo- and metal catalysts. This review collects the recent developments in catalytic enantioselective Sakurai reactions published since the beginning of 2011, including methodologies based on the use of chiral organocatalysts, metal/boron catalysts and multicatalyst systems. It is divided into three parts, dealing successively with enantioselective organocatalytic (aza)-Sakurai reactions, enantioselective metal/boron-catalyzed Sakurai reactions and enantioselective multicatalyzed (aza)-Sakurai reactions. It shows that, although still widely developed with aromatic aldehydes, the enantioselective catalytic Sakurai reaction has considerably matured in the last decade.

Reactions doi: 10.3390/reactions7010005

Authors: Sofía Estrada-Flores Tirso E. Flores-Guia Catalina M. Pérez-Berumen Luis A. García-Cerda Aurora Robledo-Cabrera Elsa N. Aguilera-González Antonia Martínez-Luévanos

Titanium oxide (TiO2) is of great interest in solar cell manufacturing, hydrogen production, and organic compound photodegradation. The synthesis variables and methodology affect the morphology, texture, crystalline structure, and phase mixtures of TiO2, which, in turn, affect the optical and catalytic properties of TiO2. In this work, the effect of acetic acid as a catalyst and chelating agent on the morphology, texture, crystal structure, optical properties, and photocatalytic activity of TiO2 samples obtained using the sol–gel method with sodium dodecyl sulfate (SDS) as a template was investigated. The results indicated that acetic acid not only catalyzes the hydrolysis of the TiO2 precursor but also acts as a chelating agent, causing a decrease in crystallite size from 18.643 nm (T7 sample, pH = 6.8, without addition of acetic acid) to 16.536 nm (T2 sample, pH = 2). At pH 2 and 3, only the anatase phase was formed (T2 and T3 samples), whereas at pH 5 and 6.8, in addition to the anatase phase, the brookite phase (11.4% and 15.61% for samples T5 and T7, respectively) was formed. The band-gap value of TiO2 decreased with decreasing pH during synthesis. Although the T2 sample had the highest specific surface area and pore volume (232.02 m2g−1 and 0.46 gcm−3, respectively), the T3 sample had better efficiency in methylene blue dye photodegradation because its bird-nest-like morphology improved photon absorption, promoting better photocatalytic performance.

Reactions doi: 10.3390/reactions7010004

Authors: Simen Gjelseth Antonsen Claus Jørgen Nielsen Hans Olav Hovtun Palm Yngve Henning Stenstrøm

Nitramines are nitrogen-containing organic compounds with the formula R1R2N–NO2. They are well-known as explosives and have been produced industrially for more than a century. A few nitramine-containing natural products have also been identified in recent years. Nitramines have also found their way into specific synthetic procedures, usually as intermediates, and for the last decades, the implementation of amine-based carbon capture and storage (CCS) technologies to mitigate CO2 emissions from fossil fuel combustion is of particular concern since small amounts are produced. Both environmental and health implications are of particular interest, and little is known today. The need for efficient and safe synthetic procedures is, therefore, vital for further research in the field. The present review gives a detailed summary of published methods and research post-millennium. Many new as well as well-established methods are presented. Representative examples with basic conditions and yields are given. Finally, indications for future research are discussed.

Reactions doi: 10.3390/reactions7010003

Authors: Giovanni Ghigo Sara Nicoletti Stefano Dughera

The Kabachnik–Fields (KF) reaction is a versatile three-component method for the condensation of amines, carbonyl compounds, and P–H reagents, enabling efficient synthesis of α-aminophosphonates—key bioactive and functional molecules. This review critically examines the literature from the last 25 years. However, with regard to mechanistic aspects, selected earlier seminal studies are also considered when necessary to provide a coherent and comprehensive mechanistic framework. Advances in catalyst-free methodologies, sustainable synthetic approaches, and Lewis and Brønsted acid catalysis are discussed, alongside developments in enantioselective KF reactions in the presence of chiral metal complexes or organocatalysts.

Reactions doi: 10.3390/reactions7010002

Authors: Kaihong Huo Yunlong Cai Yong He Shiyan Liu Chaoqun Xu Siyu Liu Wubin Weng Yanqun Zhu Zhihua Wang

As the energy structure evolves, low-load operation of coal-fired boilers is becoming common, posing challenges to combustion stability. This study explored the co-combustion of brown gas (HHO) with bituminous coal and anthracite in a one-dimensional furnace. Results indicate that introducing HHO significantly elevated combustion temperatures, with maximum increases of 158 °C and 207 °C, respectively. In the premixed mode, the flame front shifted upstream, indicating advanced ignition timing. Moreover, HHO co-combustion notably enhanced the combustion stability of anthracite, as reflected in stabilized furnace temperatures. With increasing HHO flow rate, CO concentrations from both bituminous coal and anthracite were reduced by over 80%. The combustion efficiency of bituminous coal reached 98%, while the combustion efficiency of anthracite increased by 19% (premixed) and 13% (staged), confirming the premixed mode’s superiority in promoting complete combustion. HHO co-combustion increased SO2 emissions but had a complex effect on NOX emissions due to the competition between NOX reduction caused by HHO and NOX formation caused by the increased combustion temperature. HHO co-combustion changed the melting point of fly ash, increased the content of Al2O3, and reduced the content of Na2O, K2O, and MgO, influencing the slagging behavior of the boiler and the subsequent management of fly ash.

Reactions doi: 10.3390/reactions7010001

Authors: Leandro Ayarde-Henríquez Cristian J. Guerra Hans Lenes Elizabeth Rincón Eduardo Chamorro

This mini-review discusses recent advances in the rigorous application of Bonding Evolution Theory (BET) to elucidate electron rearrangements in cycloaddition reactions occurring in both ground and electronically excited states. Computational studies reveal that describing bond formation and cleavage through parametric polynomials derived from the Catastrophe Theory (CT) provides a deeper and more coherent understanding of chemical bonding and reactivity. However, several existing BET applications have adopted CT concepts without fully incorporating the mathematical rigor on which BET is based, resulting in conceptual ambiguities and inaccurate interpretations. A proper implementation of BET requires evaluating the Hessian matrix at potentially degenerate critical points (CPs) of the Electron Localization Function (ELF) and assessing their relative evolution along the reaction coordinate. This systematic protocol integrates key CT principles within BET’s original framework, restoring its formal consistency. The resulting analyses have revealed correlations between electron-density symmetry and CT polynomials, relationships between these polynomials and the homolytic or heterolytic character of bond dissociation, and the development of a CT-based model for scaling bond polarity. These findings demonstrate that incorporating CT-derived functions into BET is not merely a formal refinement but a fundamental step toward achieving a more rigorous and predictive understanding of electron rearrangements in cycloadditions.

Reactions doi: 10.3390/reactions6040073

Authors: Pedro H. M. Araujó Connor Thompson Taylor C. Schulz H. Henry Lamb

Biofuels offer potential to mitigate climate change, increase energy security, and economically support farmers around the world. Licuri (Syagrus coronata) could be an important biofuel feedstock because its kernel (edible seed) has high energy content. This research investigates the optimal reaction conditions to convert fatty acids (FAs) and fatty acid methyl esters (FAMEs) (including licuri biodiesel) to hydrocarbons via deoxygenation in a trickle-bed reactor over granular Pd/C catalysts. Our results indicate that a 20 wt.% palmitic acid (PA) feed is optimum for continuous deoxygenation at 300 °C and 15 bar in 5% H2/He because of decarboxylation inhibition at higher concentrations. Deoxygenation rates are higher for PA than for methyl palmitate (MP) because of the slow initial hydrogenolysis of the methoxy bond over Pd/C. The hydrocarbon product distributions from deoxygenation of licuri biodiesel were fully consistent with FA decarboxylation and decarbonylation. A lab-prepared 5 wt.% Pd/C catalyst with higher metal dispersion provided modestly higher hydrocarbon yields from licuri biodiesel than a commercial 1 wt.% Pd/C catalyst.

Reactions doi: 10.3390/reactions6040072

Authors: Maria Carolina Theisen Isis Apolo Silveira de Borba Angélica Rocha Joaquim Fernando Fumagalli

Fused-bicyclic heteroaromatic cores are a common framework in drugs and other biologically active compounds. Those containing azine rings are widely used in drug discovery campaigns. Although these cores are very common, C–H functionalization of their azine moieties remains challenging, especially in annulation reactions. Therefore, this review highlights the progress made over the years in C–H annulation reactions that have produced these essential 6,5-fused bicyclic heteroaromatic cores for drug discovery. For that, the review was divided according to the five-membered rings moiety (pyrrole, pyrazole, imidazole, furan, thiophen, and thiazole) fused to different azines (pyridine, pyrazine, pyridazine, pyrimidine, and triazine). Although some important advances have been made over the years, there remains a need for research in synthetic methodology to expand the use of these heteroaromatic cores in biologically active compounds.

Reactions doi: 10.3390/reactions6040071

Authors: Julio C. Avalos Axel S. Martínez Eugenia Aldeco-Pérez Julieta Torres-González German Orozco

There are 880 studies focused on trivalent chrome baths, and several studies suggest the formation of Cr(III)L(H2O)52+, where L is an additive such as oxalate. The literature suggests that this compound decreases the energy needed in the electrodeposition process. We call this approach the inner-sphere complex hypothesis because these complexes are suggested, such as principal intermediate compounds. There are several disadvantages of this postulate, which are numbered in our study. This hypothesis was tested via Fourier transform infrared spectroscopy performed in attenuated total reflectance (ATR) mode. In addition, the potassium bis(oxalato) diaqua chromate (III) dihydrate (K[CrC2O42OH22]·2H2O) compound was selected as a probe molecule because it contains bridging C−O−Cr bonds, which are supposedly the largest number of bonds in the inner-sphere complexes in bath solutions. There is strong evidence of numerous bridging C−O−Cr bonds in the solid sample; conversely, in solution, Cr(III) prefers to form terminal bonds (Cr−O). These results suggest that the concentration of the inner-sphere complex is lower in solution. In solutions containing chromium (III) sulfate and oxalate anions, the concentrations of these complexes are much lower. Although some inner-sphere complexes are formed, their concentration does not seem to be relevant to the electrodeposition process. Otherwise, at high ionic strengths, the formation of ion pairs and hydrogen bonds between Cr(III) and additives is probable. Our research highlights the importance of vibrational spectroscopy in resolving the mechanics of the trivalent chrome electrodeposition process. This is the first study reporting a band of Cr−O bonds in trivalent chrome baths.

Reactions doi: 10.3390/reactions6040070

Authors: Wei Zhou Lei Zhang Guixian Liu Xiaosi Ma Xiangtai Meng

Azaoxyallyl cations, as novel and versatile three-atom components, have been widely utilized in cycloaddition reactions, with the competition between O- and N-cyclization pathways remaining a key research focus. This study investigates the mechanism and site selectivity of (3+2) cycloaddition between azaoxyallyl cations and 1,2-benzisoxazoles using density functional theory calculations. The results reveal a stepwise (3+2) addition to the C=N double bond, followed by base-assisted N-O bond cleavage and isoxazole ring-opening, leading to oxazoline (via O-cyclization) or imidazolone (via N-cyclization) derivatives. When unsubstituted 1,2-benzisoxazole is used as the substrate, O-cyclization dominates as a kinetically controlled process due to lower activation barriers, while N-cyclization, as a thermodynamically controlled process, is minor. The presence of a methyl group at the C(3) position in 1,2-benzisoxazoles completely blocks N-O bond cleavage, forcing exclusive (3+2) cycloaddition to yield less stable tricyclic products via N-cyclization rather than O-cyclization. These findings align with experimental observations and provide new mechanistic insights into the site selectivity of azaoxyallyl cation cycloadditions.

Reactions doi: 10.3390/reactions6040069

Authors: Jie Luo Zhigang Que Ke Zhang Yinxuan Fu Xiaodi Cheng Rong Huang Jinming Shi Haiwei Jiang Xianbin Ai Tonghui Deng Xianhua Qiu Chunbao Xu

Biodiesel is a green, low-carbon, and renewable fuel with the potential to substitute fossil fuels. The effects of reaction temperature (175–290 °C), residence time (5–75 min), and molar ratio of methanol to palmitic acid (6:1–35:1) on the non-catalytic esterification of palmitic acid with methanol to produce biodiesel were investigated by using a batch reactor. Moreover, the reaction parameters were optimized by using the response surface methodology (RSM), and the reaction kinetics were analyzed. The results showed that the conversion rate of palmitic acid to methyl palmitate increased to 100% as the reaction temperature rose from 175 °C to 225 °C, slightly changed until 275 °C, and then decreased to 94.81% at 290 °C. The conversion rate increased with residence time and reached the maximum value of 94.93% at 60 min. With increasing the molar ratio, the conversion rate rose to a maximum value of 85.46% at 15:1 and subsequently decreased. RSM results indicated the relative influence of factors on the conversion rate as reaction temperature > residence time > molar ratio. The optimal reaction parameters were 224 °C, 26 min, and a molar ratio of 16:1, affording a palmitic acid conversion rate of 99.30%. The esterification reaction between methanol and palmitic acid follows the first-order kinetics model.

Reactions doi: 10.3390/reactions6040068

Authors: Baoe Wang Rihong Zhang Zipeng She Yiyong Li

The treatment of refractory nitrogenous organic matter in industrial wastewater management poses challenges in the removal of organic matter and nitrogen. To address these issues, this study utilized a novel composite hydrodynamic cavitator, mainly consisting of spiral pipes and a step drain, which could generate cavitation twice per pass at the throat of the spiral pipe and the step drain of the cavitation cavity, thereby distinguishing it from other existing cavitators that produce cavitation only once per pass. The composite hydrodynamic cavitator, optimized using ANSYS 19.2 simulation software, offers significant advantages in energy utilization and mass transfer efficiency. Moreover, it generates a high concentration of hydroxyl free radicals, which are crucial for organic matter degradation. Batch experiments demonstrated the effective treatment of 4-aminophenol. Within 120 min, 4-aminophenol degradation efficiency reached 74.7% and total nitrogen concentration decreased slightly from 1.28 mg/L to 1.06 mg/L, while ammonia nitrogen concentration initially increased before decreasing from its peak value of 0.82 mg/L to 0.77 mg/L. During the cavitation treatment of 4-aminophenol, intermediate products, such as benzoquinone, were generated. Under the strong oxidizing action of hydroxyl radicals, nitrogen undergoes deamination to form ammonium ions, which were likely removed predominantly as nitrogen gas. The experimental results are anticipated to establish a foundation for the application of hydrodynamic cavitation technology in the treatment of refractory organic wastewater degradation and to support denitrification processes.

Reactions doi: 10.3390/reactions6040067

Authors: Renata Gašparová

Furo[3,2-b]pyrroles (FPs) are important members of the heteropentalene family. In particular, furo[3,2-b]pyrrole-5-carboxylates (FPcs) are commonly used as versatile building blocks for the synthesis of a large library of FP derivatives. Their structure with five potential reaction centres and an electron-rich character enables a wide range of transformations, from simple substitutions to multi-step reactions, yielding complex compounds with a furo[3,2-b]pyrrole scaffold. Many furo[3,2-b]pyrrole derivatives exhibit promising biological activity, while others have been employed in the construction of π-conjugated fused systems for optoelectronics. Efficient synthetic routes to furo[3,2-b]pyrrole derivatives are therefore of considerable interest. This review focuses on the synthetic methods leading to furo[3,2-b]pyrrole-5-carboxylates (FPcs), from the first successful attempts in the 1970s to recent approaches. Various methodologies are reported for the construction of complex molecules built from furo[3,2-b]pyrrole-5-carboxylates, emphasising their utility in the synthesis of fused heterocycles. This review also covers recent advances in screening for biological activity and applications such as fluorescent dyes.

Reactions doi: 10.3390/reactions6040066

Authors: Vinícius Augusto Campos Péret Renata Barbosa de Oliveira

Neglected tropical diseases (NTDs) remain a significant global health burden, exacerbated by the ongoing climate emergency, which alters disease distribution and increases vulnerability in affected populations. The urgent need for novel therapeutics demands innovative approaches in drug discovery, with heterocyclic compounds serving as versatile scaffolds due to their diverse electronic and structural properties that enable potent biological activity. This review highlights how green chemistry principles have been applied to the construction of bioactive heterocyclic cores relevant to NTD drug development. Key sustainable methodologies are discussed, including microwave-assisted solvent-free and green-solvent reactions, ultrasound-assisted synthesis, mechanochemical one-pot multistep strategies, and the use of ionic liquids and deep eutectic solvents as environmentally benign catalysts and reaction media. By focusing on these approaches, the review emphasizes how green synthetic strategies can accelerate the development of pharmacologically relevant heterocycles while minimizing environmental impact, resource consumption, and hazardous waste generation.

Reactions doi: 10.3390/reactions6040065

Authors: Michela Signoretto Federica Menegazzo

Catalysis remains the indispensable bedrock of modern industrial chemistry [...]

Reactions doi: 10.3390/reactions6040064

Authors: Soukaina Nehhal Majda Ben Ali Younes Abrouki Khalid Ofqir Yassine Elkahoui Najoua Labjar Hamid Nasrellah Souad El Hajjaji

Water pollution caused by synthetic dyes is a major environmental concern due to their stability, toxicity, and resistance to conventional wastewater treatments. This study presents a sustainable approach for synthesizing zinc oxide (ZnO) nanoparticles using artichoke biomass (waste) as a green precursor and enhancing their visible light photocatalytic activity through phosphorus doping. ZnO nanoparticles were successfully synthesized via a simple green route and doped with 3–6% phosphorus using NH4H2PO4. The structural, morphological, and optical properties of the resulting P-ZnO were characterized by XRD, SEM/EDX, TEM, FTIR, and UV-Vis spectroscopy. (6 wt%) Phosphorus doping effectively reduced the band gap from 3.06 eV to 2.95 eV, extended light absorption into the visible range, and improved electron–hole separation, resulting in enhanced photocatalytic performance. The P-ZnO nanoparticles were evaluated for methylene blue (MB) degradation under visible light in a photo-Fenton-like process, with H2O2 as an oxidant. The degradation efficiency reached 87.05% with 6% P-ZnO and further increased to 92.35% upon addition of H2O2. Durability and reusability tests demonstrated that the 6% P-ZnO catalyst maintained its activity and structural integrity over four consecutive cycles, indicating negligible loss of efficiency and excellent resistance to surface poisoning. The photocatalytic activity was strongly impacted by the quantity of catalyst, solution pH, and initial dye levels, with optimal performance at 0.3 g/L catalyst loading, pH 3, and lower MB concentrations.

Reactions doi: 10.3390/reactions6040063

Authors: Khalid Al-Qaysi M. Rahimnejad Ali Abdul Rahman-Al Ezzi

A series of clay–spinel nanocomposites reinforced by tungstophosphoric acid (TPA) were prepared and examined for the esterification of oleic acid. The type of spinel (ZnAl2O4 and CuAl2O4) and the weight ratio of clay-to-spinel were evaluated. The characterization results revealed that the clay–ZnAl2O4 nanocomposite formed better than the clay–CuAl2O4, with fewer other phases, such as ZnO or CuO. Moreover, clay–ZnAl2O4 showed higher pore volume and pore size, which led to higher conversion of oleic acid to biodiesel. The nanocomposite exhibited a good interaction between the spinel phase and clay, preventing the agglomeration of TPA. Assessing the weight ratio of clay-to-ZnAl2O4 (0.5, 1, and 1.5) showed that the same ratio of clay-to-spinel provided higher activity. It can be attributed to its rough surface, which facilitates vortex flow on the catalyst surface, its high pore volume (0.122 cc/g), and pore size (24.6 nm), enabling the diffusion of reactants and the egression of products, as well as its high acidic (453.9 μmol/g) and basic (731.6 μmol/g) properties. The clay–ZnAl2O4(1)–TPA with the largest particle size in the range of 10–30 nm converted 81.9% of oleic acid under the conditions of 120 °C, a 12 molar ratio of methanol-to-oleic acid, 4 wt.% of catalyst, and 4 h of reaction time. Due to both acidic and basic properties, along with its good reusability, the clay–ZnAl2O4(1)–TPA nanocatalyst can be a suitable catalyst for industrial biodiesel production via esterification and transesterification reactions.

Reactions doi: 10.3390/reactions6040062

Authors: Yuuki Kawashima Moe Koda Kenjiro Onimura Kazuhiro Yamabuki

To explore new possibilities in topological materials, we designed a tetrafunctional crosslinker composed of a [c2]daisy-chain rotaxane framework. In this study, a novel topological network polymer was successfully synthesized via an addition reaction between 3,6-dioxa-1,8-octanedithiol (DODT) and a tetrafunctional crosslinker, a [c2]daisy-chain rotaxane constructed from dibenzo-24-crown-8 ether (DB24C8) units and bearing long-chain alkenes on its four benzene rings. The resulting network polymer exhibited both high stiffness and toughness, along with excellent shape-memory properties. These characteristics were governed by a balance between plastic and elastic deformation originating from the DODT and rotaxane domains, respectively, highlighting a new design strategy for the creation of advanced topological materials.

Reactions doi: 10.3390/reactions6040061

Authors: Adriana M. Quinchia-Figueroa Nevis A. Ruiz Márquez Mariana Bustamante-Durango Mario A. Sánchez Juan C. Maya Roger Solano Farid Chejne

Biochar has emerged as a promising adsorbent for removing organic pollutants from aqueous media, with its efficiency strongly influenced by the feedstock and pyrolysis conditions. In this study, biochar produced from fique pellets under controlled pyrolysis was evaluated using methylene blue (MB) as a model contaminant. The cation exchange capacity reached up to 17 meq g−1 for biochar obtained at lower temperatures, while those produced at 700 °C showed values below the detection limit, consistent with the depletion of oxygenated functional groups observed in FTIR spectra. Batch adsorption experiments revealed removal efficiencies above 99% for biochar produced at 550 °C and 700 °C (45 min). The 700 °C biochar exhibited faster initial adsorption due to its larger surface area, whereas the 550 °C biochar achieved higher and more stable overall removal over prolonged contact times, attributed to the preservation of surface functional groups and measurable CEC. Kinetic modeling demonstrated that the adsorption process followed the Özer model, indicating heterogeneous surface interactions and diffusion-controlled steps. These results highlight the influence of pyrolysis temperature on adsorption kinetics and support the potential of biochar obtained from fique pellets as a sustainable, low-cost material for water purification and agro-industrial residue valorization.

Reactions doi: 10.3390/reactions6040060

Authors: Mariana Barboza da Silva Rosana Reis de Lima Araújo Renata Maria Rosas Garcia Almeida Carlos Eduardo de Farias Silva Maria Regina Pereira Brandão Thiago de Menezes Bernardino Larissa Nascimento Lôbo Jeniffer Mclaine Duarte de Freitas Johnnatan Duarte de Freitas

Lignocellulosic residues represent a promising source of raw material for obtaining several high-value bioproducts, including cellulose and derivatives. One of the main barriers to cellulose extraction from these residues is the presence of other components associated with the cellulose matrix, such as lignin and hemicellulose. To overcome this limitation, it is necessary to apply specific treatments to remove these constituents. In this study, the effectiveness of three chemical treatment methods in the purification of cellulose extracted from urban pruning biomass of the species Clitoria fairchildiana were evaluated, namely (i) alkaline treatment using dilute sodium hydroxide solution; (ii) alkaline treatment followed by bleaching with hydrogen peroxide; and (iii) alkaline treatment followed by bleaching with hydrogen peroxide and sodium hydroxide combined. The changes in chemical composition and thermal properties caused by each method were analyzed using techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results demonstrated that the biomass pretreatment reduced the content of impurities, lignin, and hemicellulose, increasing the cellulose content to 37.16% in the combined treatment (H2O2 + NaOH). Furthermore, the FTIR spectra revealed characteristic bands of important functional groups, which reaffirmed the chemical structure of the extracted cellulose through the identification of hydroxyl, carbonyl groups, and C-H bending vibrations. Additionally, the SEM results indicated an increase in specific surface area and greater exposure of fibrils, providing visual confirmation of the removal of constituents from the cellulosic matrix. Collectively, these results demonstrate the potential of combined chemical treatments for the valorization of Clitoria fairchildiana biomass and indicate its technical feasibility for obtaining cellulose with a higher degree of purity.

Reactions doi: 10.3390/reactions6040059

Authors: Daniela S. Mansilla Luis R. Pizzio José A. Mayoral José M. Fraile M. Rosario Torviso

Tungstophosphoric acid (TPA) has been supported on mesoporous silicas prepared using urea as the pore forming agent. The amount of urea (20, 30, or 40% w/w) influences the silica specific surface area (SBET), total pore volume (Vp), and average pore diameter (Dp). The materials synthetized using 20% w/w (SiU20) display mainly mesoporous structures, with the highest Vp and Dp values being chosen to be used as TPA support. The SiU20-TPA solids with different TPA loadings (10, 20, or 30% w/w) have been used as supports for chiral copper catalysts with bis(oxazoline) or azabis(oxazoline) ligands. The catalytic efficiency of enantioselective cyclopropanation strongly depends on support morphology and TPA loading. SiU-TPA20 has been shown to be the optimal one. The stability of the complex is also a very important parameter, and the best results are obtained with an excess of chiral ligand to ensure the correct formation of the complex on the solid. In this way, with azabox-Cu/SiU20-TPA20 it is possible to obtain a highly selective (90% ee for the trans-cyclopropanes) and recoverable catalyst.

Reactions doi: 10.3390/reactions6040058

Authors: Luis P. Amador-Gómez Delia Hernández-Romero José M. Rivera-Villanueva Sharon Rosete-Luna Carlos A. Cruz-Cruz Enrique Méndez-Bolaina Elena de la C. Herrera-Cogco Rafael Melo-González Agileo Hernández-Gordillo Raúl Colorado-Peralta

Biodiesel is an alternative, sustainable, renewable, and environmentally friendly energy source, which has generated interest from the scientific community due to its low toxicity, rapid biodegradability, and zero carbon footprint. Biodiesel is a biofuel produced by the transesterification of triglycerides or the esterification of free fatty acids (FFA). Both reactions require catalysts with numerous active sites (basic, acidic, bifunctional, or enzymatic) for efficient biodiesel production. On the other hand, since the late 1990s, metal–organic frameworks (MOFs) have emerged as a new class of porous materials and have been successfully used in various fields due to their multiple properties. For this reason, MOFs have been used as heterogeneous catalysts or as a platform for designing active sites, thus improving stability and reusability. This literature review presents a comprehensive analysis of using MOFs as heterogeneous catalysts or supports for biodiesel production. The optimal parameters for transesterification/esterification are detailed, such as the alcohol/feedstock molar ratio, catalyst amount, reaction time and temperature, conversion percentage, biodiesel yield, fatty acid and water content, etc. Additionally, novel methodologies such as ultrasound and microwave irradiation for obtaining MOF-based catalysts are described. It is important to note that most studies have shown biodiesel yields >90% and multiple reuse cycles with minimal activity loss. The bibliographic analysis was conducted using the American Chemical Society (ACS) Scifinder® database, the Elsevier B.V. Scopus® database, and the Clarivate Analytics Web of Science® database, under the institutional license of the Universidad Veracruzana. Keywords were searched for each section, generally limiting the document type to “reviews” and “journals,” and the language to English, and published between 2000 and 2025.

Reactions doi: 10.3390/reactions6040057

Authors: Lakshmi Mohanraj Ranjitha Jambulingam

This study investigates the efficiency of biocarbon derived from Prosopis juliflora shells in removing Astrazon pink dye from aqueous solutions. The biocarbon obtained from the thermochemical process was characterised using FTIR Spectroscopy, SEM microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), and XRD. Batch adsorption experiments were conducted to assess various factors, including the Potential of Hydrogen (pH), Dosage of biocarbon, Astrazon pink dye concentration, temperature, and Time of contact. Similarly, Adsorption isotherm models, including the Langmuir and the Freundlich isotherms, were used to evaluate the adsorption capacity. In contrast, pseudo-first-order and pseudo-second-order models were used to analyse the kinetics of dye adsorption. The interactive effects of selected variables on the removal of Astrazon Pink dye from synthetic water were determined using Response Surface Methodology (RSM). The maximum dye uptake, 98.54%, was achieved with a biochar dose of 8 g/L at 50 ppm dye concentration, pH 7.5, and 35 °C. The Freundlich adsorption isotherm model and the pseudo-second-order kinetic model are the better-fitting models for the dye adsorption process, with R2 values of 0.99. Consequently, the thermodynamic parameters indicate that the process is endothermic and spontaneous.

Reactions doi: 10.3390/reactions6040056

Authors: Denis Opra Sergey Sinebryukhov Alexander Sokolov Andrey Gerasimenko Sviatoslav Sukhoverkhov Andrey Sidorin Alexandra Zavidnaya Sergey Gnedenkov

Searching anode materials is an important task for the development of sodium-ion batteries. In this regard, bronze-phase titanium dioxide, TiO2(B), has been considered as one of the promising materials, owing to its crystal structure with open channels and voids facilitating Na+ diffusion and storage. However, the electrochemical de-/sodiation mechanism of TiO2(B) has not been clearly comprehended, and further experiments are required. Herein, in situ and ex situ observations by a combination of X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, gas chromatography–mass spectrometry was used to provide additional insights into the electrochemical reaction scenario of bronze-phase TiO2 in Na-ion batteries. The findings reveal that de-/sodiation of TiO2(B) occurs through a reversible intercalation reaction and without the involvement of the conversion reaction (no metallic titanium is formed and no oxygen is released). At the same time, upon the first Na+ uptake process, crystalline TiO2(B) becomes partially amorphous, but is still driven by the Ti4+/Ti3+ redox couple. Importantly, TiO2(B) has pseudocapacitive electrochemical behavior during de-/sodiation based on a quantitative analysis of the cyclic voltammetry data. The results obtained in this study complement existing insights into the sodium storage mechanisms of TiO2(B) and provide useful knowledge for further improving its anode performance for SIBs application.

Reactions doi: 10.3390/reactions6040055

Authors: Safiya Mallah Mariam El Mchaouri Salma El Meziani Hafida Agnaou Hajar El Haddaj Wafaa Boumya Noureddine Barka Alaâeddine Elhalil

Green synthesis represents a sustainable, reliable, and eco-friendly approach for producing various materials and nanomaterials, including metal and metal oxide nanoparticles. This environmentally conscious method has garnered significant attention from materials scientists. In recent years, interest in plant-mediated nanoparticle synthesis has grown markedly, owing to advantages such as enhanced product stability, low synthesis costs, and the use of non-toxic, renewable resources. This review specifically focuses on the green synthesis of metal oxide nanoparticles using plant extracts, highlighting five key oxides: TiO2, ZnO, WO3, CuO, and Fe2O3, which are prepared through various plant-based methods. The release of toxic effluents like synthetic dyes into the environment poses serious threats to aquatic ecosystems and human health. Therefore, the application of biosynthesized nanoparticles in removing such pollutants from industrial wastewater is critically examined. This paper discusses the synthesis routes, characterization techniques, green synthesis methodologies, and evaluates the photocatalytic performance and dye degradation mechanisms of these plant-derived nanoparticles.

Reactions doi: 10.3390/reactions6040054

Authors: William Thomas Möller Svava Dögg Hreinsdóttir Luis Antonio Arana Benjamín Ragnar Sveinbjörnsson

The regioselectivity of the Claisen rearrangement with different meta-substituted and meta- and para-substituted allyl phenyl ethers was investigated. The main results were that in meta-substituted Claisen rearrangements the regioselectivity depends roughly on the electronic nature of the substituent, with electron-donating groups favoring migration further from the meta-substituent while electron-withdrawing groups favor migration towards the meta-substituent. Different para-substituents were tested with two meta-substituents, Me, and Cl. Most of the para-substituent tested had a clear effect on the product ratio, in all but one case enhancing the proportion of the major product favored by the meta-substituent. Population analysis was performed with Mulliken, Löwdin, Hirshfeld, and natural population analysis to analyze the influence of the substituents on the atomic charges on the reaction sites. It was observed that the atomic charge on the carbon that forms the major isomer is of higher negativity than the atomic charge on the carbon that forms the minor isomer.

Reactions doi: 10.3390/reactions6040053

Authors: Thaís Marques Uber Danielly Maria Paixão Novi Luana Yumi Murase Vinícius Mateus Salvatori Cheute Samanta Shiraishi Kagueyama Alex Graça Contato Rosely Aparecida Peralta Adelar Bracht Rosane Marina Peralta

Fungal laccases are promising oxidative enzymes for bioremediation applications, particularly in the degradation of synthetic dyes present in industrial effluents. Here, we evaluated the inhibitory effects of sodium chloride (NaCl) and sodium sulfate (Na2SO4) on the activity of Trametes versicolor laccase and its ability to decolorize Congo Red (CR), Malachite Green (MG), and Remazol Brilliant Blue R (RBBR). Enzyme assays revealed concentration-dependent inhibition, with IC50 values of 0.22 ± 0.04 M for NaCl and 1.00 ± 0.09 M for Na2SO4, indicating stronger inhibition by chloride. Kinetic modeling showed mixed-type inhibition for both salts. Despite this effect, the enzyme maintained significant activity: after 12 h, decolorization efficiencies reached 95 ± 4.0% for MG, 88 ± 3.0% for RBBR, and 75 ± 3.0% for CR, even in the presence of 0.5 M salts. When applied to a mixture of the three dyes, decolorization decreased only slightly in saline medium (94.04 ± 4.0% to 83.43 ± 5.1%). FTIR spectra revealed minor structural changes, but toxicity assays confirmed marked detoxification, with radicle length in lettuce seeds increasing from 20–38 mm (untreated dyes) to 41–48 mm after enzymatic treatment. Fungal growth assays corroborated reduced toxicity of treated dyes. These findings demonstrate that T. versicolor laccase retains functional robustness under ionic stress, supporting its potential application in saline textile wastewater remediation.

Reactions doi: 10.3390/reactions6040052

Authors: Xin Li Yali Yao Xinying Liu

With their considerable capacity and structurally favorable characteristics, layered transition metal oxides have become strong contenders for cathode use in sodium-ion batteries (SIBs). Nevertheless, their practical deployment is challenged by pronounced capacity loss, predominantly induced by unstable cathode–electrolyte interphase (CEI) at elevated voltages. In this study, difluoroethylene carbonate (DFEC) is introduced as a functional electrolyte additive to engineer a robust and uniform CEI. The fluorine-enriched CEI effectively suppresses parasitic reactions, mitigates continuous electrolyte decomposition, and facilitates stable Na+ transport. Consequently, Na/NaNi1/3Fe1/3Mn1/3O2 (Na/NFM) cells with 2 wt.% DFEC retain 78.36% of their initial capacity after 200 cycles at 1 C and 4.2 V, demonstrating excellent long-term stability. Density functional theory (DFT) calculations confirm the higher oxidative stability of DFEC compared to conventional solvents, further supporting its interfacial protection role. This work offers valuable insights into electrolyte additive design for high-voltage SIBs and provides a practical route to significantly improve long-term electrochemical performance.

Reactions doi: 10.3390/reactions6040051

Authors: Nelson N. dos Santos Marcos F. Silva Alexandre F. Young Marcos L. Dias Mariana M. V. M. Souza

The coordination chemistry of benzimidazole ligands combines σ donation and π backbonding. Owing to this electronic flexibility, benzimidazole ligands stabilize both electron deficient and electron-rich transition states in the catalytic cycle of Ziegler-Natta polymerizations. In this study, Fe(III) and Ni(II) complexes of 2-substituted-benzimidazoles were tested as catalysts for ethylene and 1-butene oligomerization. The tests realized in toluene yielded mainly butenes and minor amounts of hexenes. When dichloromethane was used as solvent, a tandem reaction took place and 1-butene produced by ethylene dimerization was further oligomerized, yielding octenes and dodecenes as main products. All tested catalysts exhibited moderate selectivity for 1-octene, indicating 1-ω enchainment in 1-butene dimerization. Beyond catalytic tests, a theoretical study of the ligand 2,2′-(furan-2,5-diyl)bis(1H-benzimidazole) confirmed the planar structure of this compound as evidenced by NMR spectroscopy.

Reactions doi: 10.3390/reactions6030050

Authors: Riny Yolandha Parapat Irsan Asfari Khoirin Reygina Katon Cahyani Najla Septariani Sabrina Putri Nurlian Freddy Haryanto Muhammad Nadhif Noer Hamdhan Michael Schwarze

The growing accumulation of waste lubricating oil presents serious environmental issues, calling for sustainable management solutions. This research discusses the creation of FeNi/TiO2 nanocatalysts that were synthesized through an eco-friendly method utilizing grape seed extract (GSE) as a natural reducing agent for the catalytic pyrolysis of waste lubricating oil. The nanocatalyst was produced using the microemulsion technique and refined via Response Surface Methodology (RSM) to optimize its catalytic performance. Pyrolysis was carried out at 400 °C, leading to a significant conversion of waste oil into valuable fuel. The FeNi/TiO2 nanocatalyst exhibited exceptional capabilities in facilitating the breakdown of heavy hydrocarbons into lighter fuel fractions while reducing unwanted byproducts. GC-MS analysis demonstrated the prevalence of C6–C20 hydrocarbons in the pyrolysis oil, underscoring its potential as a high-quality alternative fuel similar to traditional diesel. This study aids in the progress of environmentally sustainable waste-to-energy technologies, offering a promising pathway for effective fuel production and hazardous waste management.

Reactions doi: 10.3390/reactions6030049

Authors: Angappan Mano Priya Gisèle El Dib

Nerol ((Z)-3,7-dimethylocta-2,6-dien-1-ol), (C10H18O), is a monoterpene alcohol that belongs to the family of BVOCs emitted naturally by means of vegetation and is found in various medicinal plants. This species attracted attention in the field of atmospheric chemistry due to its unique structural, chemical and environmental properties. In this work, OH-addition and H-abstraction reactions of Nerol by OH radical have been investigated using M06-2X, CBS-QB3 and CCSD(T) with 6-311++G(d,p) basis set. The OH addition at the C=C double bond of Nerol was shown to be the most favorable, with a small relative energy barrier of −6.86 kcal/mol and H-abstraction at the CH2 group exhibits a relative energy barrier of 0.08 kcal/mol at CCSD(T)/6-311++G(d,p) level of theory. The obtained overall rate coefficient at 298 K is 9.68 × 10−10 cm3 molecule−1 s−1 using canonical variational transition state theory with small curvature tunnelling method (CVT/SCT), which is in good agreement with the experimental rate coefficient determined by Mahecha et al. (kOH = (1.60 ± 0.2) × 10−10) at 296 ± 2 K. The obtained rate coefficient exhibits negative temperature dependence, and the atmospheric lifetime of Nerol is about 18 min. The predicted oxidation pathways reveal the formation of key products such as formaldehyde, glycolaldehyde and 6-Methyl-hept-5-en-2-ol, which is also observed in previous experimental studies, indicating good agreement between theoretical and experimental findings. This study constitutes the first theoretical study and its dependence on temperature exploration, offering detailed insights into the degradation pathways and environmental impact of Nerol initiated by hydroxyl radicals.

Reactions doi: 10.3390/reactions6030048

Authors: Leandro A. G. Jesus Adinaldo L. M. P. Silva Rosane A. S. San Gil Leandro B. Borré Luiz C. Bertolino Ricardo S. S. Teixeira

Two new long-chain N-alkyl imidazole derivatives, 2-(1-octadecyl-imidazol-2-yl)pyridine and 2-(furan-2-yl)-1-(octadecane-1-yl)-1H-imidazole, were synthesized via the Radziszewski reaction followed by N-alkylation. This is the first report of furan-imidazole obtained by this route using furfuraldehyde as a renewable biomass-derived precursor. FTIR, 1D/2D solution NMR, and HRMS confirmed the structural elucidation, while XRD and solid-state 13C CPMAS NMR corroborated the crystal structures of the precursors. Notably, previously misassigned 1H and 13C chemical shifts reported in the literature for pyridine and furan-imidazole precursors were corrected. Furthermore, 13C CPMAS NMR spectra of those precursors are reported here for the first time. These findings expand the scope of the Radziszewski reaction and provide new insights into the structural characterization of imidazole-based systems.

Reactions doi: 10.3390/reactions6030047

Authors: Eva E. Soto-Guzmán Antonio J. Oliveros-Ortiz Armando Talavera-Alemán Mónica A. Calderón-Oropeza Gabriela Rodríguez-García Brenda Y. Bedolla-García Mario A. Gómez-Hurtado Carlos M. Cerda-García-Rojas Jérôme Marrot Christine Thomassigny Rosa E. del Río

Strategic scaffolds in molecules increase the possibility of obtaining derivatives with potential uses in scientific and industrial areas. The regio- and stereoselective reactions can be considered to gain these tactical motifs. Natural diterpenes are key molecules for reaching such aims. Among this class of compounds, neo-clerodanes are highlighted by the presence of a furan moiety in their chemical structure. This work describes a regio- and stereoselective strategy to gain beta-lactone and oxirane derivatives from kerlinic acid (1) when the β,γ-unsaturated carboxylic acid system is oxidized, preserving the furan moiety. Oxidation of 1 yielded salviaolide (2), suggesting regio- and stereoselective means. A reaction mechanism was proposed when oxidation of the acetate (1a), benzoate (1b), and methyl ester (1c) derivatives from 1 were gained. The obtention of the epoxide derivative 3, kernolide (4), and kernolide epoxide (5) also supported the reaction mechanism. X-ray diffraction analysis of 3, Karplus-type analyses, and DFT calculations from hypothetical intermediates revealed conformational preferences that guide the regioselectivity. The stereoselectivity was attributed to the natural origin of 1. All compounds were characterized by their physical and spectroscopical data. These results suggest the feasibility of promoting regioselective oxidation on neo-clerodane compounds, preserving the furan moiety.

Reactions doi: 10.3390/reactions6030046

Authors: Yvonne Gemmecker Iris Schall Andreas Seubert Nicole Paczia Johann Heider

The NAD+-dependent alcohol dehydrogenase AdhB from Aromatoleum aromaticum EbN1 belongs to family III of Fe-dependent alcohol dehydrogenases. It was recombinantly produced in Escherichia coli and biochemically characterized, showing activity only with ethanol or n-propanol. The enzyme contained substoichiometric amounts of Fe, Zn, and Ni and a yet unidentified nucleotide-like cofactor, as indicated by mass spectrometric data. As suggested by its narrow substrate spectrum and complementation of a related species to growth on ethanol, the most probable physiological function of AdhB is the oxidation of short aliphatic alcohols such as ethanol or n-propanol. The enzyme also exhibits a very high tolerance to ethanol and n-propanol, showing moderately substrate-inhibited Michaelis–Menten kinetics up to concentrations of 20% (v/v). AdhB can also be applied biotechnologically to convert acetate to ethanol in coupled enzyme assays with the tungsten enzyme aldehyde oxidoreductase, showing activity with either another aldehyde or pre-reduced benzyl viologen as electron donors.

Reactions doi: 10.3390/reactions6030045

Authors: Zonia Bibi Muhammad Ajmal Shahaab Jilani Aqsa Kamran Fatima Yaseen Muhammad Abid Zia Ahmed Lakhani Muhammad Ali Hashmi

Carbon dioxide is naturally present in the Earth’s atmosphere and plays a role in regulating and balancing the planet’s temperature. However, due to various human activities, the amount of carbon dioxide is increasing beyond safe limits, disrupting the Earth’s natural temperature regulation system. Today, CO2 is the most prevalent greenhouse gas; as its concentration rises, significant climate change occurs. Therefore, there is a need to utilize anthropogenically released carbon dioxide in valuable fuels, such as formic acid (HCOOH). Single-atom catalysts are widely used, where a single metal atom is anchored on a surface to catalyze chemical reactions. In this study, we investigated the potential of Cu@Phosphorene as a single-atom catalyst (SAC) for CO2 reduction using quantum chemical calculations. All computations for Cu@Phosphorene were performed using density functional theory (DFT). Mechanistic studies were conducted for both bimolecular and termolecular pathways. The bimolecular mechanism involves one CO2 and one H2 molecule adsorbing on the surface, while the termolecular mechanism involves two CO2 molecules adsorbing first, followed by H2. Results indicate that the termolecular mechanism is preferred for formic acid formation due to its lower activation energy. Further analysis included charge transfer assessment via NBO, and interactions between the substrate, phosphorene, and the Cu atom were confirmed using quantum theory of atoms in molecules (QTAIM) and non-covalent interactions (NCI) analysis. Ab initio molecular dynamics (AIMD) calculations examined the temperature stability of the catalytic complex. Overall, Cu@Phosphorene appears to be an effective catalyst for converting CO2 to formic acid and remains stable at higher temperatures, supporting efforts to mitigate climate change.

Reactions doi: 10.3390/reactions6030044

Authors: Rodrigo Gomes de Araujo Caio Eduardo Canin de França Joelma Perez

The nitrogen electroreduction reaction (NRR) has emerged as a promising and sustainable alternative to the Haber–Bosch process for NH3 production. This study investigated the NRR in alkaline medium using Pd/C, Rh/C, and PdRh/C electrocatalysts, employing online electrochemical mass spectrometry (OLEMS) for gaseous-product detection and ultraviolet–visible spectroscopy to confirm NH3 formation. To our knowledge, no previous reports have simultaneously detected H2, N2H, and N2H2 intermediates and monitored N2 consumption as a function of applied potential for Pd and Rh catalysts. The bimetallic PdRh/C catalyst showed superior NRR performance compared with the monometallic catalysts, exhibiting higher faradaic charges, more pronounced generation of nitrogen intermediates, and selectivity for NH3. This work provides key insights into the NRR mechanisms and underlines the strategic importance of the bimetallic catalyst design for more efficient, sustainable electrochemical NH3 synthesis.

Reactions doi: 10.3390/reactions6030043

Authors: Fabrizio Machetti Donatella Giomi Alberto Brandi

Cycloadditions are among the most efficient chemical processes because they combine atom economy and high levels of selectivity—particularly regio- and stereoselectivity—with the ability to generate molecular complexity in a single step [...]

Reactions doi: 10.3390/reactions6030042

Authors: Karinne E. Prado Micael R. Cunha Gabriela A. Moreira Karoline B. Waitman Neuza M. A. Hassimotto Katlin B. Massirer Monica F. Z. J. Toledo Roberto Parise-Filho

A new series of 6-arylaminoflavones was synthesized via the Buchwald–Hartwig cross-coupling reaction, aiming to functionalize the flavone core efficiently. Reaction optimization revealed that Pd2(dba)3/XantPhos with Cs2CO3 in toluene provided the best yields, with isolated yields ranging from 8% to 95%, depending on the arylamine structure. Steric hindrance and electron-withdrawing groups at the arylamine ring impacted the reaction outcomes. Cytotoxicity assays in different human cancer cell lines indicated that substitution patterns at both the arylamine and B-rings strongly impacted biological activity. In particular, compounds bearing a 3,4-dimethoxy substitution at the B-ring and a trifluoromethyl (13c) or chlorine (13g) group at the aniline moiety exhibited enhanced cytotoxicity. These findings provide insights into the structure–activity relationship of 6-arylaminoflavones while contributing to the development of synthetic methodologies for functionalized flavones.

Reactions doi: 10.3390/reactions6030041

Authors: Sara Ahmed Harry Burrows Brian A. Chalmers David B. Cordes Ruairidh Macleod Davidson Lauren Emmens Theodore V. Fulton Daniel Kleinjan Iain L. J. Patterson Iain A. Smellie

Polycyclic aromatic compounds can often be made by a sequence featuring an initial Diels–Alder [4 + 2] cycloaddition reaction, followed by cheletropic extrusion of carbon monoxide. These reactions normally require heating the diene and dieneophile in petrochemical-derived aromatic hydrocarbon solvents, such as xylenes or diphenyl ether. This article summarizes the results of attempts to use renewable solvents in place of those currently in use to prepare pentaphenylbenzene and 1,2,4-triphenyltriphenylene. Dihydrolevoglucosenone, p-cymene, ethyl lactate, diethyl carbonate, and cyclopentyl methyl ether have all been successfully evaluated as renewable solvent alternatives in Diels–Alder/cheletropic reaction sequences. An analysis of the products from the reactions investigated did not show evidence of oxidative degradation of the diene reactants. Furthermore, norbornadien-7-one intermediates were not isolated from any of the reactions tested.

Reactions doi: 10.3390/reactions6030040

Authors: Theresa Coetsee Frederik De Bruin

Aluminothermic reduction is an alternative processing route for the circular economy because Al is produced electrochemically in the Hall–Héroult process with minimal CO2 emissions if the electricity input is sourced from non-fossil fuel energy sources. This circular processing option attracts increased research attention in the aluminothermic production of manganese and silicon alloys. The Al2O3 product must be recycled through hydrometallurgical processing, with leaching as the first step. Recent work has shown that the NaAlO2 compound is easily leached in water. In this work, a suitable slag formulation is applied in the aluminothermic reduction of manganese ore to form a Na2O-based slag of high Al2O3 solubility to effect good alloy–slag separation. The synergistic effect of carbon and silicon reductants with aluminium is illustrated and compared to the test result with only carbon reductant. The addition of small amounts of carbon reductant to MnO2-containing ore ensures rapid pre-reduction to MnO, facilitating aluminothermic reduction. At 1350 °C, a loosely sintered mass formed when carbon was added alone. The alloy and slag chemical analyses are compared to the thermochemistry predicted phase chemistry. The alloy consists of 66% Mn, 22–28% Fe, 2–9% Si, 0.4–1.4% Al, and 2.2–3.5% C. The higher %Si alloy is formed by adding Si metal. Although the product slag has a higher Al2O3 content (52–55% Al2O3) compared to the target slag (39% Al2O3), the fluidity of the slags appears sufficient for good alloy separation.

Reactions doi: 10.3390/reactions6030039

Authors: Afonso Santine M. M. Velez Daniela Pinheiro Carlos Serpa Rosane Nora Castro Marco Edilson Freire de Lima Otávio Augusto Chaves

Dye-sensitized solar cells (DSSCs) have emerged as a promising technology for converting sunlight into electricity at a low cost; however, it is still necessary to find a photostable, low-cost, and efficient photosensitizer. In this sense, the natural product bixin (Dye 1) has previously been reported as a potential photosensitizer. Thus, the present work reports the full synthesis of diester and diacid hybrids (Dyes 2 and 3, respectively, with corresponding yields of 93% and 52%) using the natural product bixin as a starting material and 1,3,4-oxadiazole ring as a connected point. The hydrolysis step of Dye 2 aims to obtain Dye 3 with a structural capacity to anchor the titanium dioxide (TiO2) nanofilms via the carboxylic acid group. Both compounds (Dyes 1 and 3) can be adsorbed via pseudo-first order on the surface of TiO2 nanofilms, reaching saturation after 10 and 6 min of exposure in an organic solution (1 × 10−5 M), respectively, with adsorption kinetics of the semisynthetic compound almost twofold higher than the natural product. Contrary to expectations, Dye 3 had spectral behavior similar to Dye 1, but with better frontier molecular orbital (FMO) parameters, indicating that Dye 3 will probably behave very similarly or have slightly better photovoltaic performance than Dye 1 in future DSSC measurements.

Reactions doi: 10.3390/reactions6030038

Authors: Eveleen A. Dawood Thamer J. Mohammed Buthainah Ali Al-Timimi Eman H. Khader

The disposal of wastewater resulting from petroleum industries presents a major environmental challenge due to the presence of hard-to-degrade organic pollutants, such as oils and hydrocarbons, and high chemical oxygen demand (COD). In this study, an efficient and eco-friendly method was developed to treat such wastewater using a photocatalyst composed of biochar derived from pistachio shells and loaded with zinc oxide (ZnO) nanoparticles. The biochar-ZnO composite was prepared via a co-precipitation-assisted pyrolysis method to evaluate its efficiency in the photocatalytic degradation of petroleum wastewater (PW). The synthesized material was characterized using various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy, to determine surface morphology, crystal structure, and functional groups present on the catalyst surface. Photocatalytic degradation experiments were conducted under UV and sunlight for 90 h of irradiation to evaluate the performance of the proposed system in removing oil and reducing COD levels. Key operational parameters, such as pH (2–10), catalyst dosage (0–0.1) g/50 mL, and oil and COD concentrations (50–500) ppm and (125–1252) ppm, were optimized by response surface methodology (RSM) to obtain the maximum oil and COD removal efficiency. The oil and COD were removed from PW (90.20% and 88.80%) at 0.1 g/50 mL of PS/ZnO, a pH of 2, and 50 ppm oil concentration (125 ppm of COD concentration) under UV light. The results show that pollutant removal is slightly better when using sunlight (80.00% oil removal, 78.28% COD removal) than when using four lamps of UV light (77.50% oil removal, 75.52% COD removal) at 0.055 g/50 mL of PS/ZnO, a pH of 6.8, and 100 ppm of oil concentration (290 ppm of COD concentration). The degradation rates of the PS/ZnO supported a pseudo-first-order kinetic model with R2 values of 0.9960 and 0.9922 for oil and COD. This work indicates the potential use of agricultural waste, such as pistachio shells, as a sustainable source for producing effective catalysts for industrial wastewater treatment, opening broad prospects in the field of green and nanotechnology-based environmental solutions in the development of eco-friendly and effective wastewater treatment technologies under solar light.

Reactions doi: 10.3390/reactions6020037

Authors: Zhenliang Pan Lulu Wu Liangxin Fan Wankai An Guoyu Yang Cuilian Xu

A new synthetic route of Epalrestat was proposed in this study. The new route abandons the raw material carbon disulfide, which is highly harmful to the environment, and optimizes the key steps in the typical synthesis strategy. Epalrestat was prepared through a three-step process, and the reaction products were characterized. The optimum conditions for the synthesis of the substituted rhodanine intermediate are as follows: under the catalysis of 2.0 equivalents of 25%KOH, ethanol was used as the solvent, and the reaction was carried out at 40 °C for 1 h. The optimal conditions for the synthesis of Epalrestat are as follows: under the catalysis of 2.0 equivalents of 50%KOH, ethanol was used as the solvent, and the reaction was carried out at 40 °C for 5 h.

Reactions doi: 10.3390/reactions6020036

Authors: Debora Pratesi Alessio Morano Andrea Goti Francesca Cardona Camilla Matassini

1,3-Dipolar cycloadditions on nitrone dipoles are key reactions to access five-membered heterocycles, which are useful intermediates in the synthesis of biologically relevant glycomimetics. The good atomic balance and high stereoselectivity characteristic of such reactions make them good candidates for the development of green protocols. In the present work, these features were maximized by avoiding the use of organic solvents and considering starting materials derived from biomass. Reactions involving (acyclic and cyclic) carbohydrate-derived nitrones as dipoles and levoglucosenone as dipolarophile were considered. Performing selected 1,3-dipolar cycloadditions in neat conditions showed reduced reaction times, maintaining similar selectivity and yields with respect to the classical protocols. The use of microwave irradiation and orbital shaking were also exploited to increase the sustainability of the synthetic protocols. The collected results highlight the potential of solvent-free 1,3-dipolar cycloadditions in the design of efficient synthetic routes according to green chemistry principles, such as prevention, atom economy, safer solvents and auxiliaries, and use of renewable feedstocks.

Reactions doi: 10.3390/reactions6020035

Authors: Juhua Feng Wenjie Zou Haokun Zhang Qilin Huang Ailin Huang Kuan Liu Guizhou Yue

In this study, we develop a concise and efficient synthetic strategy for the construction of eight-membered cyclic diaryl sulfides by undertaking [3+2] cycloaddition, 1,2-hydrogen shift, and C(sp2)-S bond cleavage steps on 2-methylenebenzothiophene-3-ones with aryne, using TBAT as the fluorine source. This transformation proceeds well under mild conditions and affords the target products in high to excellent yields (up to 93% yields). The process provides a practical route to achieving sulfur-containing medium-sized heterocycles.

Reactions doi: 10.3390/reactions6020034

Authors: Sofiane Hocine Victor Cosson Remi Calandrino Timea Baló Jayson Alves Bordelo Sébastien Triboulet Laure Caruana Laurence Klipfel Sandrine Calis András Herner Stephen Hanessian

We describe the design and synthesis of a series of N-[arylsulfonyl]-1H-pyrrole-2-carboxamides as hybrid analogs of the DCAF15 binders E7820 and tasisulam, two representative SPLAMs (sulfonamide-containing molecular glues). These hybrid molecules were designed to combine the key interactions of both parent ligands within the DCAF15 binding site, as supported by docking studies. Binding affinity was evaluated using fluorescence polarization assays, and structure–activity relationships were established, highlighting the importance of dichlorinated pyrrole moieties. Selected compounds were also tested in HCT116 cells to assess in vitro activity.

Reactions doi: 10.3390/reactions6020033

Authors: Tarsila Santos da Silva Laura Leticia Freitas Ferreira da Silva Evellyn Patricia Santos da Silva Rayssa Jossanea Brasileiro Motta Bruno José Barros da Silva Mario Roberto Meneghetti Lucas Meili Simoni Margareti Plentz Meneghetti

Mixed oxides were obtained via calcination at 550 °C from layered double hydroxides (LDHs), which were synthesized in a previous study via co-precipitation and co-precipitation followed by hydrothermal treatment using aluminum residues as the source of this element. After characterization, these oxides (Mg-Al-LDH-CP and Mg-Al-LDH-H, named according to the synthesis methods of the precursor LDHs) were applied as heterogeneous catalysts in the methyl transesterification of ethyl acetate (EA). The formation of mixed oxides was confirmed by the absence of basal peaks associated with the layered LDH structure in the XRD analysis, due to calcination. Further characterization revealed that Mg-Al-LDH-CP exhibited the highest number of acidic sites, while Mg-Al-LDH-H had the highest number of basic sites. The transesterification activity was evaluated in the reaction between ethyl acetate (EA) and methanol (MeOH). The best result, obtained under a molar ratio of 1:5:0.005 (EA:MeOH:catalyst) at 120 °C, was a 63% conversion after 360 min of reaction for the Mg-Al-LDH-CP catalyst, which had a higher number of acidic sites and fewer basic sites. Additionally, the catalysts demonstrated robustness, maintaining catalytic activity over four cycles without a significant decrease in performance. These results indicate the feasibility of using mixed oxides derived from LDH, synthesized from aluminum residues, as heterogeneous catalysts in transesterification reactions, highlighting their potential for advancing more sustainable catalyst development.

Reactions doi: 10.3390/reactions6020032

Authors: Krishnamoorthy Uma Sivakami Sundararajan Vaideeswaran Ambrose Rosevenis Rajender Boddula Kanagarajan Shenbagam Muniraj Balaganesh Usan Pathinathan Saleth Prabhakar Paramasivam Shanmugam Fatemah M. Barakat Supakorn Boonyuen Ramyakrishna Pothu

The unique properties of lanthanum oxide nanoparticles (La2O3NPs) make them highly suitable for various environmental applications. This study explores the plant-based synthesis of La2O3NPs using Drypetes sepiaria as a reducing agent. The synthesized La2O3NPs were characterized through a range of spectroscopic and microscopic techniques. Scanning electron microscopy (SEM) revealed that the La2O3NPs have an uneven surface and a stony appearance. A morphological analysis indicated that the nanoparticles range in size from 20 to 50 nm. The appreciable band gap energy values were concluded as 5.5 eV. The crystal structure and elemental composition were determined using X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The results from the microplate assay method demonstrated enhanced anti-biofilm properties, and photocatalytic tests showed significant dye-degradation capabilities. The degradation efficiency and zone inhibition values of the La2O3NPs were found to be 90.12% and 39.18%, respectively.

Reactions doi: 10.3390/reactions6020031

Authors: Wenping Ma Jia Yang Gary Jacobs Robert Pace Dali Qian

Unlike on Fe and Co catalysts, the CO conversion effect on Ru catalyst performance is little reported. This study is undertaken to explore the issue using a series of Ru/NaY catalysts under 200–230 °C, 2.0 MPa, H2/CO = 2, and 10–60% CO conversion in a 1 L continuous stirred tank reactor (CSTR). The results are comparatively studied with those of Fe and Co catalysts reported previously. The NaY support and four 1.0%, 2.5%, 5.0%, and 7.5% Ru/NaY catalysts were characterized by BET, H2 chemisorption, H2O-TPD, XRD, HRTEM, and XANES/EXAFS techniques. The BET and XRD results suggest a high surface area (730 m2/g), high degree of crystallinity of the NaY support, and high dispersion of Ru, while an hcp Ru structure and well-reduced Ru were reflected in the HR-TEM FFT and XANES/EXAFS results. The reaction results indicate that the CO conversion effect on CH4 and C5+ selectivities on the Ru is the same as that on the Fe and Co catalysts, with CH4 selectivity decreasing and C5+ selectivity increasing with increasing CO conversion. However, the CO conversion effect on olefin formation for the Ru catalyst was found to be opposite to that of the Fe and Co; increasing CO conversion enhanced olefin formation but suppressed secondary reactions of 1-olefins. The H2O cofeeding experiments showed that H2O impacted olefin formation by suppressing hydrogen adsorption and hydrogenation. The H2O-TPD experiment evidenced a much stronger H2O adsorption capacity (6.8 mmol/g-cat) on Ru followed by Co (1 mmol/g-cat), and then Fe (0.2 mmol/g-cat)., which showed only a very low H2O adsorption capacity.This finding may explain the opposite CO conversion effect on olefin formation observed on the Ru catalyst, and may also explain why low CH4 selectivity (i.e., 3%) occurred on the Ru catalyst and high CH4 selectivity (i.e., 6–8%) occurred on the Co catalyst, both of which possess low water gas shift (WGS) activity.

Reactions doi: 10.3390/reactions6020030

Authors: Shuqin Miao Xiaojiong Wu Delong Ding Chunliang Ge Weihua Shen Yi Yang Yunjin Fang

Polypropylene carbonate (PPC) is a biodegradable material derived from propylene oxide (PO) with the renewable resource CO2. In this study, PPC was prepared by the catalytic polymerization of CO2 with PO using a zinc glutarate/zinc cobalt double metal cyanide (ZnGA/DMC) composite catalyst prepared from two heterogeneous catalysts, zinc glutarate (ZnGA) and zinc cobalt double metal cyanide (Zn-Co DMC). High selectivity of PPC was achieved among the polymer and propylene carbonate. The prepared PPC had high molecular weight. The thermal stability of the PPC product was obviously improved by the optimization of the reaction conditions. The catalytic effect of the composite catalyst was superior to that of individual ZnGA and Zn-Co DMC, overcoming the shortcomings of those two catalysts. And the composite catalyst also stimulated some synergistic effects between the two composites, which significantly improved the catalytic effect.

Reactions doi: 10.3390/reactions6020029

Authors: Lihong Chen Xiufei Zhao Kuo Zhang Biyu Wu Xiao Yang Haonan Zou Lei Zhang Huahao Shao Tianyi Ma Hu Zhou Yusheng Zhang

The development of efficient and stable photocatalysts is critical for addressing water pollution challenges caused by persistent organic contaminants. However, single-component photocatalysts often suffer from rapid photogenerated carrier recombination and limited visible-light absorption. In this study, a two-dimensional lamellar stacked Bi2O3/CeO2 type-II heterojunction photocatalyst (BC) was successfully synthesized in situ by a topological transformation strategy induced by high-temperature oxidation of monolithic Bi. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses confirmed the uniform distribution of Bi2O3 nanosheets on CeO2 surfaces, forming an intimate interfacial contact that enhances charge separation and transfer efficiency. Photoluminescence (PL) spectroscopy, UV–visible diffuse reflectance spectroscopy (DRS), and electrochemical characterization revealed extended visible-light absorption (up to 550 nm) and accelerated electron migration in the heterojunction. Under simulated sunlight, the optimized BOC (3:1) composite exhibited a ciprofloxacin (CIP) degradation rate constant 2.30 and 5.63 times higher than pure Bi2O3 and CeO2, respectively. Theoretical calculations validated the type-II band alignment with conduction and valence band offsets of 0.07 eV and 0.17 eV, which facilitated efficient spatial separation of photogenerated carriers. This work provides a rational strategy for designing heterojunction photocatalysts and advancing their application in water purification.

Reactions doi: 10.3390/reactions6020028

Authors: Javier E. Morales-Mendoza Jorge L. Domínguez-Arvizu Alma B. Jasso-Salcedo Blanca C. Hernández-Majalca José L. Bueno-Escobedo Alejandro López-Ortiz Virginia H. Collins-Martínez

Achieving net-zero carbon emissions, this study introduces a sustainable pathway for reducing strontium sulfate (SrSO4) and celestite ore to strontium sulfide (SrS) using biofuels (biomethane, bioethanol) derived from agro-industrial waste and green hydrogen. Traditional SrSO4 reduction methods, which rely on fossil-derived reductants like coal and operate at energy-intensive temperatures (1100–1200 °C), generate significant greenhouse gases and toxic byproducts, highlighting the need for eco-friendly alternatives. Experimental results demonstrate that bioethanol outperformed other reductants, achieving 97% conversion of synthetic SrSO4 at 950 °C within 24 min and 74% conversion of natural celestite ore over 6 h. Remarkably, this bioethanol-driven process matches the energy efficiency of the conventional black ash method while enabling carbon neutrality through renewable feedstock utilization, reducing CO2 emissions by 30–50%. By valorizing agro-industrial waste streams, this strategy advances circular economy principles and aligns with Mexico’s national agenda for sustainable industrial practices, including its commitment to decarbonizing heavy industries. This study contributes to sustainable development goals and offers a scalable solution for decarbonizing strontium compound production in the chemical industry.

Reactions doi: 10.3390/reactions6020027

Authors: Ewa M. Iwanek (nee Wilczkowska) Aleksandra Goździk Zbigniew Kaszkur

This study shows how important the coordination of Al3+ ions in the silver support is for the overall activity in soot combustion. Five silver catalysts with a silver content of 14.7 wt.% were prepared using the following supports: α-Al2O3, which has only octahedrally coordinated Al3+, θ-Al2O3, which has both octahedrally and tetrahedrally coordinated Al3+, and zeolites, which contain only tetrahedrally coordinated Al3+: 10X, 13X, and 5A. The analysis of the diffraction patterns showed that silver on the surface of catalysts made with the first four supports was mainly in the metallic form, except for Ag/5A in which there was a lack of reflections from Ag0 in the XRD pattern. Nevertheless, the difference in the activity of the support and the catalyst as well as the EDX results indicate the presence of silver on the catalyst. The SEM-EDX analysis showed that the silver dispersion strongly depends on the support and that even the zeolites with large silver particles on the surface have silver evenly distributed across the surface. The activity of the catalysts decreased in the following series: Ag/Al 1200 > Ag/5A ≈ Ag/13X > Ag/10X ≈ Ag/Al 550. Time-of-Flight Secondary Ion Mass Spectrometry was used to delve into the reason why the catalyst with the low-surface area α-Al2O3 support yielded a better catalyst than that obtained using the high-surface area alumina support and showed that different ratios of secondary ions were emitted from the two surfaces.

Reactions doi: 10.3390/reactions6020026

Authors: Kryslaine M. A. Santos Simone J. Canhaci Rafael F. Perez Marco A. Fraga

Glucose is the most abundant monosaccharide as it is the primary unit of cellulose and starch, which are the more relevant feedstocks for biorefineries. Dehydration of glucose can lead to anhydroglucoses, whose interest has been increasing due to its potential industrial use. Commercial sulfonic polymer resins and a synthesized organic–inorganic mesoporous material were taken as Brønsted acid catalysts. High hexose conversion (up to 98%) and selectivity to anhydroglucoses (~80%) could be reached, turning this process into an alternative route to carbohydrate pyrolysis that presents an energy-intensive downstream. Hexose conversion to anhydroglucoses was related to the amount of acid sites, and the removal of one molecule of water from hexoses to produce anhydroglucoses was found as the preferential dehydration route over a bare Brønsted acid catalyst in anhydrous polar aprotic solvent (DMF) at mild conditions. Product distribution changed dramatically upon catalyst deactivation with HMF and fructose emerging as relevant products. It was suggested that an additional Lewis surface is produced during the deactivation process, probably arising from the formation of insoluble high molecular weight compounds in acidic media.

Reactions doi: 10.3390/reactions6020025

Authors: Stevan Stojadinović

This review analyzes TiO2-based coatings formed by the plasma electrolytic oxidation (PEO) process of titanium for the photocatalytic degradation of methyl orange (MO) under simulated solar irradiation conditions. PEO is recognized as a useful technique for creating oxide coatings on various metals, particularly titanium, to assist in the degradation of organic pollutants. TiO2-based photocatalysts in the form of coatings are more practical than TiO2-based photocatalysts in the form of powder because the photocatalyst does not need to be recycled and reused after wastewater degradation treatment, which is an expensive and time-consuming process. In addition, the main advantage of PEO in the synthesis of TiO2-based photocatalysts is its short processing time (a few minutes), as it excludes the annealing step needed to convert the amorphous TiO2 into a crystalline phase, a prerequisite for a possible photocatalytic application. Pure TiO2 coatings formed by PEO have a low photocatalytic efficiency in the degradation of MO, which is due to the rapid recombination of the photo-generated electron/hole pairs. In this review, recent advances in the sensitization of TiO2 with narrow band gap semiconductors (WO3, SnO2, CdS, Sb2O3, Bi2O3, and Al2TiO5), doping with rare earth ions (example Eu3+) and transition metals (Mn, Ni, Co, Fe) are summarized as an effective strategy to reduce the recombination of photo-generated electron/hole pairs and to improve the photocatalytic efficiency of TiO2 coatings.

Reactions doi: 10.3390/reactions6020024

Authors: Kuo Zhang Xiufei Zhao Hang Qian Lihong Chen Biyu Wu Xiao Yang Haonan Zou Yujiao Hu Feng Chen Borong Liao Hu Zhou Lei Zhang Tianyi Ma Yusheng Zhang

Cu2O, a narrow-bandgap semiconductor with visible light absorption capabilities, faces limitations in photocatalytic applications due to photocorrosion from hole self-oxidation and insufficient light absorption. In this work, a series of novel spherical Cu2O/FePO4 Z-scheme heterojunctions were successfully synthesized via self-assembly to overcome these challenges. The photocurrent, electrical impedance spectroscopy (EIS), and photoluminescence (PL) tests showed that Cu2O/1.5FePO4 (CF1.5) had excellent electron hole separation efficiency. Subsequently, photocatalytic degradation was utilized as a probing technique to further confirm the above conclusions, with the kinetic reaction constants of CF1.5 being 2.46 and 11.23 times higher than those of Cu2O and FePO4, respectively. After five cycles of experiments and XPS analysis, it was found that the content of Cu(I) in CF1.5 did not significantly decrease after the reaction, indicating that it has superior anti-photocorrosion performance compared to single Cu2O, which is also due to the establishment of a Z-scheme heterojunction. Systematic studies using radical scavenging experiments and ESR tests identified ·OH and ·O2− as the main active species involved in photocatalysis. The formation of a Z-scheme heterojunction not only enhances the photocatalytic activity of the CF1.5 composite but also effectively suppresses the photocorrosion of Cu2O, thereby offering a promising approach for enhancing anti-photocorrosion of Cu2O.

Reactions doi: 10.3390/reactions6020023

Authors: Yassine Elkahoui Fatima-Zahra Abahdou Majda Ben Ali Said Alahiane Mohamed Elhabacha Youssef Boutarba Souad El Hajjaji

The development of heterostructures incorporating photocatalysts optimized for visible-light activity represents a major breakthrough in the field of environmental remediation research, offering innovative and sustainable solutions for environmental purification. This study explores the photocatalytic capabilities of a SnFe2O4/g-C3N4 heterojunction nanocomposite, successfully synthesized from graphitic carbon nitride (g-C3N4) and tin ferrate (SnFe2O4) and applied to the degradation of the cationic dye brilliant cresyl blue (BCB) in an aqueous solution. These two components are particularly attractive due to their low cost and ease of fabrication. Various characterization techniques, including XRD, FTIR, SEM, and TEM, were used to confirm the successful integration of SnFe2O4 and g-C3N4 phases in the synthesized catalysts. The photocatalytic and photo-Fenton-like activity of the heterojunction composites was evaluated by the degradation of brilliant cresyl blue under visible LED illumination. Compared to the pure components SnFe2O4 and g-C3N4, the SnFe2O4/g-C3N4 nanocomposite demonstrated a superior photocatalytic performance. Furthermore, the photo-Fenton-like performance of the composites is much higher than the photocatalytic performances. The significant improvement in photo-Fenton activity is attributed to the synergistic effect between SnFe2O4 and g-C3N4, as well as the efficient separation of photoexcited electron/hole pairs. The recyclability of the SnFe2O4/g-C3N4 composite toward BCB photo-Fenton like degradation was also shown. This study aimed to assess the modeling and optimization of photo-Fenton-like removal BCB using the SnFe2O4/g-C3N4 nanomaterial. The main parameters (photocatalyst dose, initial dye concentration, H2O2 volume, and reaction time) affecting this system were modeled by two approaches: a response surface methodology (RSM) based on a Box–Behnken design and artificial neural network (ANN). A comparison was made between the predictive accuracy of RSM for brilliant cresyl blue (BCB) removal and that of the artificial neural network (ANN) approach. Both methodologies provided satisfactory and comparable predictions, achieving R2 values of 0.97 for RSM and 0.99 for ANN.

Reactions doi: 10.3390/reactions6020022

Authors: Md Masud Rana Bhuiyan Basudeb Saha

A heterogeneous polybenzimidazole-supported Mo(VI) catalyst and tert-butyl hydroperoxide (TBHP) as an oxidising reagent have been utilised to establish a more environmentally friendly and greener alkene epoxidation process. A polybenzimidazole-supported Mo(VI) complex (PBI.Mo) has been prepared, characterised and evaluated successfully. The stability and catalytic activity of the produced catalyst have been evaluated for the epoxidation of 1,7-octadiene and 1,5-hexadiene in a jacketed stirred batch reactor to assess its performance towards these alkenes. The suitability and efficiency of the catalyst have been compared by studying the effect of reaction temperature, feed mole ratio of alkene to TBHP, catalyst loading, and reaction time on the yield of 1,2-epoxy-5-hexene and 1,2-epoxy-7-octene. Response surface methodology (RSM) using Box–Behnken Design (BBD) has been employed to design experimental runs and study the catalytic performance of the PBI.Mo catalyst for all batch experimental results. A quadratic regression model has been developed representing an empirical relationship between reaction variables and response, which is the yield of epoxides. The numerical optimisation technique concluded that the maximum yield that can be reached is 66.22% for 1,7-octadiene and 64.2% for 1,5-hexadiene. The reactivity of alkenes was observed to follow the sequence 1,5-hexadiene > 1,7-octadiene. The findings of this study confirm that the optimal reaction conditions vary between the two reactions, indicating differences in catalytic performance for each alkene.

Reactions doi: 10.3390/reactions6010021

Authors: Juan Soto

In this work, we studied the main decomposition reactions on the ground state of nitromethane (CH3NO2) with the CASPT2 approach. The energetics of the main elementary reactions of the title molecule have been analyzed on the basis of Gibbs free energies obtained from standard expressions of statistical thermodynamics. In addition, we describe a mapping method (orthogonalized 3D representation) for the potential energy surfaces (PESs) by defining an orthonormal basis consisting of two Rn orthonormal vectors (n, internal degrees of freedom) that allows us to obtain a set of ordered points in the plane (vector subspace) spanned by such a basis. Geometries and harmonic frequencies of all species and orthogonalized 3D representations of the PESs have been computed with the CASPT2 approach. It is found that all of the analyzed kinetically controlled reactions of nitromethane are endergonic. For such a class of reactions, the dissociation of nitromethane into CH3 and NO2 is the process with the lower activation energy barrier (ΔG); that is, the C-N bond cleavage is the most favorable process. In contrast, there exists a dynamically controlled process that evolves through a roaming reaction mechanism and is an exergonic reaction at high temperatures: CH3NO2 → [CH3…NO2]* → [CH3ONO]* → CH3O + NO. The above assertions are supported by CASPT2 mappings of the potential energy surfaces (PESs) and classical trajectories obtained by “on-the fly” CASSCF molecular dynamics calculations.

Reactions doi: 10.3390/reactions6010020

Authors: Ravi Devarajappa Scarlett Kiyeleko Sofiane Hocine Victor Cosson Remi Calandrino Timea Baló Jayson Alves Bordelo Sébastien Triboulet Laure Caruana Laurence Klipfel Sandrine Calis András Herner Stephen Hanessian

We describe the design and synthesis of a series of 7-(N-aryl pyrrolidinyl) indoles and oxo-analogs as isosteric mimics of the DCAF15 binder E7820, a well-known member of aryl sulfonamides known as SPLAMs. The functionalization of C-7 in indoles was achieved by metal-catalyzed CH-activation with unexpected results. Binding assays revealed the pyrrolidine N-aryl carboxylic acid analog to be as equally active as E7820.

Reactions doi: 10.3390/reactions6010019

Authors: Marcio Jose da Silva Cesar Macedo Oliveira Pedro Henrique da Silva Andrade Neide Paloma Gonçalves Lopes

In this work, tin and zinc salts of silicotungstic and phosphotungstic acids were synthesized, characterized, and tested as catalysts for esterification reactions of glycerol with acetic acid (HOAc) to produce glycerol esters such as monoacetyl glycerol (MAG), which are used as additives in the pharmaceutical and food industries and in the manufacturing of explosives, or, in the case of di- or triacetyl glycerol (DAG and TAG), green bioadditives for diesel or gasoline. The activity of metal-exchanged salts (Zn, Sn) in H3PW12O40 and H4SiW12O40 heteropolyacids was evaluated in esterification reactions at room temperature. Among the catalysts tested, Sn2/3PW12O40 was the most active and selective toward the glycerol esters. The process’s selectivity can be controlled by changes to reaction conditions. The maximum selectivitiesy of DAG and TAG were 60% and 30%, respectively, using a 1:3 molar ratio of glycerol/HOAc and a Sn3/2PW12O40/673 K catalyst load of 0.4 mol%. Under these conditions, a glycerol conversion rate of 95% was observed and selectivity towards DAG and TAG was observed at 60% and 30%, respectively. The results were achieved after an 8 h reaction at a temperature of 333 K. The Sn3/2PW12O40/673 K catalyst demonstrated the highest efficiency, which was attributed to its higher degree of acidity.

Reactions doi: 10.3390/reactions6010018

Authors: Mirtha Z. L. L. Ribeiro Igor F. Gomes Edher Z. Herrera Alexandre Mello Marília O. Guimarães Patrícia A. Carneiro Débora C. M. Rodrigues Wanderlã L. Scopel Rodrigo G. Amorim Mauro C. Ribeiro

This study combines experimental and density functional theory (DFT) to evaluate the influence of alkaline cation characteristics on the electronic structure and photodegradation efficacy of organic dyes in MNbO3 (M = Na, K) perovskites. The X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Near Edge Spectroscopy (XANES) spectra at the Nb edge of the Perovskites were employed to characterize its chemical and structural properties. The DFT calculations were carried out to simulate XANES spectra as well as the structural and electrical properties of KNbO3 and NaNbO3. Our results show that the simulated and experimental XANES spectra are similar, indicating that the computational simulations were able to capture the local structure of the niobate samples. In addition, a photocatalytic experiment was conducted to benchmark the methylene blue consumption efficiency between different niobates. The findings demonstrated that KNbO3 is more efficient than NaNbO3 for methylene blue UV photocatalytic degradation, which is associated with their electronic properties. This arises as a direct result of the variably deformed NbO6 octahedra resulting from the different alkali used. Our findings facilitate the advancement of stable and abundantly available photocatalysts, which may be employed for energy-intensive processes such as the mineralization of organic water pollutants and hydrogen production by water splitting.

Reactions doi: 10.3390/reactions6010017

Authors: Georgeta Serban Faïza Diaba

The palladium-catalyzed cross-coupling reaction used for carbon–carbon bond formation is one of the most commonly applied reactions in modern organic synthesis. In this work, a concise strategy was developed for constructing the tetrahydroisoquinoline core, a key structural motif found in many biologically active compounds. This method involves the palladium-catalyzed intramolecular coupling of aryl iodides with ester enolates generated in the presence of K3PO4 as a base, resulting in the formation of the tetrahydroisoquinoline ring with an exceptionally high yield of 84%.

Reactions doi: 10.3390/reactions6010016

Authors: Mirosław K. Szukiewicz Natalia Patulska Elżbieta Chmiel-Szukiewicz

In this study, the application of the response surface method was used to determine the best reaction conditions of the gas-phase hydrogenation of carbon dioxide on a commercial nickel-based catalyst. The procedural goals included the choice and tests of the robustness of the statistical method that could improve the achievement of the goal of the process, first of all by reducing the number of necessary experiments. The outcome goal for the process under consideration was the optimization of reaction conditions for mild reaction conditions and the stoichiometric deficiency of hydrogen; these reaction conditions are rarely presented in the literature (despite their potential advantages). Both goals were achieved with a successful result. To find optimal reaction conditions, only 36 experiments were carried out. This is a very good result, taking into account the insufficient information in the literature, which means that it is a difficult task to deduce the region of the highest carbon dioxide conversion. The maximum carbon dioxide conversion was obtained for a temperature of 318 °C and a ratio of molar fluxes of H2 to CO2 equal to 3.5. It should be emphasized that this result was confirmed experimentally.

Reactions doi: 10.3390/reactions6010015

Authors: Sanjib Kumar Karmee Sreedhar Gundekari Louis C. Muller Ajinkya Hable

Glycerol is a biogenic waste that is generated in both the biodiesel and oleo-chemical industries. The value addition of surplus glycerol is of utmost importance for making these industries economically profitable. In line with this, glycerol is converted into glycerol carbonate, a potential candidate for the industrial production of polymers and biobased non-isocyanate polyurethanes. In addition, glycerol can also be converted into solketal, which is the protected form of glycerol with a primary hydroxyl functional group. In this contribution, we developed a microwave-assisted solvent and catalyst-free method for converting solketal into solketal carbonate. Under conventional heating conditions, the reaction of solketal with dimethyl carbonate resulted in 70% solketal carbonate in 48 h. However, under microwave heating, 90% solketal carbonate was obtained in just 30 min. From the perspective of sustainability and green chemistry, biomass-derived heterogeneous catalysts are gaining importance. Therefore, in this project, several green catalysts, such as molecular sieves (MS, 4Å), Hβ-Zeolite, Montmorillonite K-10 clay, activated carbon from groundnut shell (Arachis hypogaea), biochar prepared from the pyrolysis of sawdust, and silica gel, were successfully used for the carbonyl transfer reaction. The obtained solketal carbonate was thoroughly characterized by 1H NMR, 13C NMR, IR, and MS. The method presented here is facile, clean, and environmentally benign, as it eliminates the use of complicated procedures, toxic solvents, and toxic catalysts.

Reactions doi: 10.3390/reactions6010014

Authors: Jhonathan Castillo-Saenz Jorge Salomón-Carlos Ernesto Beltrán-Partida Benjamín Valdez-Salas

Cerium oxide nanoparticles (CeO2-NPs) offer promising advantages in semiconductors and biomedical applications due to their optical, electrical, antioxidant, and antibacterial properties. However, the widely reported synthetic strategies for CeO2-NPs demand toxic precursors and intermediary pollutants, representing a major limitation to CeO2-NPs applications. Therefore, it is necessary to develop greener strategies that implicate ecological precursors to reduce the negative impact on the scalability of CeO2-NPs. In this regard, we applied Lycium cooperi (L. cooperi) aqueous extracts as an unexplored potential green reducing agent for the eco-friendly synthesis of CeO2-NPs. The L. cooperi extract showed the presence of alkaloids, flavonoids, cardiac glycosides, and carbohydrate-derived families, which were assessed for spherical monodispersed CeO2-NPs under a rapid chemical reduction. Moreover, the elemental composition revealed Ce and O, indicating highly pure CeO2-NPs characterized by an interplanar cubic crystalline structure. Furthermore, we detected the presence of stabilizing functional groups from L. cooperi, which, after a controlled annealing process, resulted in a band gap energy of 3.9 eV, which was optimal for the CeO2-NPs. Thus, the results indicate that L. cooperi is an environmentally friendly synthesis method that can open a new route for CeO2-NPs in biomedical and industrial applications.

Reactions doi: 10.3390/reactions6010013

Authors: Julie Hessevik Cathinka S. Carlsen Oskar K. Bestul David Waller Helmer Fjellvåg Anja O. Sjåstad

Metallic Pd/Ni gauzes, located downstream of the Pt/Rh ammonia oxidation catalyst nets in the Ostwald process, is the current technology for capturing volatile gas phase platinum and rhodium species lost from the Pt/Rh combustion catalyst through evaporation. In this screening study, we explore four oxide families, ABO3 perovskites, (ABO3)n(AO) Ruddlesden–Popper (RP) phases, AO rock salt, and A2O3 sesquioxide type oxides, as alternative materials for platinum capture. It was found that all the tested nickelates, LaNiO3, NdNiO3, La2NiO4, and La4Ni3O10, captured platinum well and formed A2NiPtO6. In contrast, La0.85Sr0.15FeO3, LaFeO3, and LaCoO3 did not capture platinum. CaO, SrO, and Nd2O3 formed low-dimensional platinates such as CaxPt3O4, Sr4PtO6, and a newly discovered neodymium platinate, Nd10.67Pt4O24. Gd2O3 did not capture platinum in bench-scale experiments in dry air, but did, however, seem to capture platinum under pilot plant conditions, likely due to the co-capture of Co lost from the N2O abatement catalyst. The catalytic activity of both oxides and platinum-containing products were studied, toward NOx and N2O decomposition. None of the oxides showed significant activity toward NOx decomposition, and all showed activity toward N2O decomposition, but to different extents. An overall assessment of the screened oxides with respect to potential use in industrial Ostwald conditions is provided. All tested oxides except CaO and SrO withstood industrial conditions. From our assessments, the nickelates and A2O3 (A = Nd, Gd) stand out as superior oxides for platinum capture.

Reactions doi: 10.3390/reactions6010012

Authors: Hanifi Yaman Mirza Talha Baig Asgar Kayan

New tetrasubstituted porphyrin tin complexes (5–14) were prepared in two different ways: In the first preparation procedure, tin porphyrin complexes were prepared by a direct reaction of butyltin trichloride and dibutyltin dichloride with tetra/tetrakis(4-X-phenyl)porphyrins (X = H, F, Cl, Br, CF3, CH3O, and (CH3)2N). In the second procedure, the same tin porphyrin complexes were synthesized from the reaction of butyltin trichloride and dibutyltin dichloride with lithium porphyrinato derivatives. These novel tin complexes were characterized by elemental analysis, 1H, 13C NMR, FTIR, UV-Vis spectroscopy, and mass spectrometry. Among these complexes, tin porphyrin containing methoxy group [Bu2Sn(TMOPP)] was tested as an adsorbent to remove tetracycline antibiotics from wastewater. The TTC antibiotic removal efficiency (R%) of this complex was measured using UV-Vis spectroscopy. After 120 min of equilibration, the final R% and adsorption capacity (qt) were measured at 60.15% and 18.10 mg/g, respectively.