Reactions

Research

Jump to: Review

13 pages, 2006 KB

Open AccessArticle

Hydrodeoxygenation of Black Liquor HTL Oil Model Compounds in Supercritical Water

by Sari Rautiainen, Tyko Viertiö, Niko Vuorio, Felix Hyppönen, Luděk Meca, Pavel Kukula and Juha Lehtonen

Reactions 2026, 7(1), 7; https://doi.org/10.3390/reactions7010007 - 20 Jan 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Graphical abstract

15 pages, 3004 KB

Open AccessArticle

Trivalent Chromium Electroplating Baths—The Inner-Sphere Complex Hypothesis

by Julio C. Avalos, Axel S. Martínez, Eugenia Aldeco-Pérez, Julieta Torres-González and German Orozco

Reactions 2025, 6(4), 71; https://doi.org/10.3390/reactions6040071 - 8 Dec 2025

Viewed by 320

Abstract

There are 880 studies focused on trivalent chrome baths, and several studies suggest the formation of

{[C r (I I I) L (H_{2} O)_{5}]}^{2 +}

, where

L

is an additive such as oxalate. The literature [...] Read more.

There are 880 studies focused on trivalent chrome baths, and several studies suggest the formation of

{[C r (I I I) L (H_{2} O)_{5}]}^{2 +}

, 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 [C r {(C_{2} O_{4})}_{2} {(O H_{2})}_{2}] \cdot 2 H_{2} O

) compound was selected as a probe molecule because it contains bridging

C - O - C r

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 - C r

bonds in the solid sample; conversely, in solution,

C r (I I I)

prefers to form terminal bonds (

C r - 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

C r (I I I)

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

C r - O

bonds in trivalent chrome baths. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

10 pages, 1449 KB

Open AccessArticle

Enhanced Cycling Stability of High-Voltage Sodium-Ion Batteries via DFEC-Driven Fluorinated Interface Engineering

by Xin Li, Yali Yao and Xinying Liu

Reactions 2025, 6(4), 52; https://doi.org/10.3390/reactions6040052 - 1 Oct 2025

Viewed by 1599

Abstract

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. [...] Read more.

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/NaNi_1/3Fe_1/3Mn_1/3O₂ (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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

19 pages, 1656 KB

Open AccessArticle

An Iron-Dependent Alcohol Dehydrogenase Is Involved in Ethanol Metabolism of Aromatoleum aromaticum

by Yvonne Gemmecker, Iris Schall, Andreas Seubert, Nicole Paczia and Johann Heider

Reactions 2025, 6(3), 46; https://doi.org/10.3390/reactions6030046 - 1 Sep 2025

Viewed by 1612

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Graphical abstract

28 pages, 6457 KB

Open AccessArticle

Photocatalytic and Photo-Fenton-like Degradation of Cationic Dyes Using SnFe₂O₄/g-C₃N₄ Under LED Irradiation: Optimization by RSM-BBD and Artificial Neural Networks (ANNs)

by Yassine Elkahoui, Fatima-Zahra Abahdou, Majda Ben Ali, Said Alahiane, Mohamed Elhabacha, Youssef Boutarba and Souad El Hajjaji

Reactions 2025, 6(2), 23; https://doi.org/10.3390/reactions6020023 - 28 Mar 2025

Cited by 5 | Viewed by 2324

Abstract

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-C₃ [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

19 pages, 6227 KB

Open AccessArticle

Comparative Study of Greener Alkene Epoxidation Using a Polymer-Supported Mo(VI) Complex: Performance Evaluation and Optimisation via Response Surface Methodology

by Md Masud Rana Bhuiyan and Basudeb Saha

Reactions 2025, 6(2), 22; https://doi.org/10.3390/reactions6020022 - 24 Mar 2025

Viewed by 1111

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

17 pages, 4491 KB

Open AccessArticle

CASPT2 Study of the Unimolecular Reactions of Nitromethane—A Look at the Roaming Reactions in the Decomposition of Nitromethane: An Exergonic Route at High Temperatures

by Juan Soto

Reactions 2025, 6(1), 21; https://doi.org/10.3390/reactions6010021 - 12 Mar 2025

Cited by 1 | Viewed by 2314

Abstract

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 [...] Read more.

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

R^{n}

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

10 pages, 1316 KB

Open AccessCommunication

Palladium-Catalyzed α-Arylation of Esters: Synthesis of the Tetrahydroisoquinoline Ring

by Georgeta Serban and Faïza Diaba

Reactions 2025, 6(1), 17; https://doi.org/10.3390/reactions6010017 - 1 Mar 2025

Cited by 1 | Viewed by 2024

Abstract

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 [...] Read more.

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%. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

Review

Jump to: Research

33 pages, 10526 KB

Open AccessReview

Recent Developments in the Catalytic Enantioselective Sakurai Reaction

by Hélène Pellissier

Reactions 2026, 7(1), 6; https://doi.org/10.3390/reactions7010006 - 10 Jan 2026

Viewed by 182

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Graphical abstract

32 pages, 3554 KB

Open AccessReview

Synthetic Strategies for Nitramines: From Energetic Materials to Atmospheric Byproducts

by Simen Gjelseth Antonsen, Claus Jørgen Nielsen, Hans Olav Hovtun Palm and Yngve Henning Stenstrøm

Reactions 2026, 7(1), 4; https://doi.org/10.3390/reactions7010004 - 7 Jan 2026

Viewed by 255

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Graphical abstract

36 pages, 6309 KB

Open AccessReview

The Kabachnik–Fields Reaction: A Key Transformation in Organophosphorus Chemistry

by Giovanni Ghigo, Sara Nicoletti and Stefano Dughera

Reactions 2026, 7(1), 3; https://doi.org/10.3390/reactions7010003 - 4 Jan 2026

Viewed by 321

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Graphical abstract

28 pages, 12427 KB

Open AccessReview

Photocatalytic Degradation of Methyl Orange in Wastewater Using TiO₂-Based Coatings Prepared by Plasma Electrolytic Oxidation of Titanium: A Review

by Stevan Stojadinović

Reactions 2025, 6(2), 25; https://doi.org/10.3390/reactions6020025 - 8 Apr 2025

Cited by 4 | Viewed by 2968

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Feature Papers in Reactions in 2025

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Related Special Issues

Published Papers (12 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI