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Hexanal, hexenal, nonenal and their corresponding alcohols are used as green notes in the fragrance and flavour industry. The production of bio-based hexanal starts from linoleic acid, which can be obtained from sunflower or safflower oil. The biocatalytic process utilizes C₁₃-specific lipoxygenase (LOX) for hydroperoxidation and consecutive splitting with hydroperoxide lyase (HPL). In this study, we investigated the chemical splitting of the LOX product 13-HPODE in comparison to HPL catalysis. In addition, 13-HPODE was synthesized using enriched linoleic acid from safflower oil. Varying amounts of soybean flour suspension as a source of LOX yielded up to 60% HPODE with a regioselectivity of 92% towards 13-HPODE. Using low-toxicity Lewis acids like AlCl₃ and ZrCl₄, cleavage of the produced 13-HPODE was possible. A maximum hexanal yield of 22.9% was reached with AlCl₃ under mild reaction conditions, though product degradation was an interfering process. Comparative trials with N-terminal truncated HPL from papaya revealed hexanal recovery within a comparable range. Additionally, we successfully demonstrated the viability of Hock rearrangement of 13-HPODE through heterogeneous catalysts. Notably, Beta zeolite and Montmorillonite K10 exhibited a turnover frequency (TOF) on par with common heterogeneous catalysts employed in industrial processes. Full article

Green synthesis of silver nanoparticles (AgNPs) involves a reduction reaction of a metal salt solution mixed with a plant extract. The reaction yield can be controlled using several independent factors, such as extract and metal concentration, temperature, and incubation time. AgNPs from Origanum vulgare (oregano) were synthesized in the past. However, no investigations were performed on the combined effects of independent factors that affect the synthesis. In this work, silver nitrate, oregano extract, and sodium hydroxide (NaOH) concentrations were chosen as the independent factors, and full factorial design under Response Surface Methodology was employed. UV–Vis absorbance spectroscopy, X-ray Powder Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were used to characterize the nanoparticles. A Voigt function was fitted on the measured UV–Vis spectra. The fitting parameters of the Voigt function, peak wavelength, area, and Full Width at Half Maximum, were used as the responses. A quadratic model was fitted for the peak wavelength and area. The NaOH concentration proved to be the dominant factor in nanoparticle synthesis. UV–Vis absorbance showed a characteristic plasmon resonance of AgNPs at 409 nm. XRD verified the crystallinity of the nanoparticles and FTIR identified the ligands involved. Full article

Pyrazole, characterized by a five-membered heterocyclic structure featuring two neighboring nitrogen atoms, serves as a core element. Pyrazoles hold a privileged status as versatile frameworks in various sectors of the chemical industry, including medicine and agriculture. Previous reviews have extensively highlighted the significance of pyrazoles and their diverse biological activities, encompassing roles such as antituberculosis, antimicrobial, antifungal, anti-inflammatory, anticancer, and antidiabetic agents. Consequently, they have garnered substantial interest from researchers. The aim of this review is to offer a comprehensive overview of the published research related to the synthesis of pyrazole derivatives, encompassing a discussion of diverse methods for accessing the pyrazole moiety. These methods span from utilizing transition-metal catalysts and photoredox reactions to employing one-pot multicomponent processes, novel reactants, and innovative reaction types. It encompasses studies conducted by numerous scientists worldwide, showcasing collective efforts in advancing the methodologies and applications of pyrazole derivatives. Full article

γ-valerolactone (GVL) is a crucial chemical feedstock used in the production of fuel additives, renewable fuels, and fine chemicals alternative to petroleum-based solvents and chemicals, supporting the transition to sustainable energy solutions. It is promptly acquired by hydrogenating levulinic acid (LA) in a gaseous or liquid phase with a homogeneous or heterogeneous catalyst using a variety of recognized catalytic processes. Herein, this work focuses on the use of silica-supported copper (Cu/SiO₂) catalysts for the gas-phase hydrogenation of LA to GVL under mild reaction conditions. The study analyzes how copper loading can affect the catalytic activity of the Cu/SiO₂, while the flow rate of LA, time-on-stream, reaction temperature, and LA concentration affect the catalytic efficiency. The SiO₂ support’s various Cu loadings are crucial for adjusting the catalytic hydrogenation activity. One of the studied catalysts, a 5 wt% Cu/SiO₂ catalyst, demonstrated ~81% GVL selectivity with ~78% LA conversion and demonstrated stability for ~8 h while operating at atmospheric pressure and temperature (265 °C) and 0.5 mL/h of LA flow rate. The ability to activate hydrogen, high amount of acidic sites, and surface area were all discovered to be advantageous for increased GVL selectivity. Full article

Rotaxanes, known as supramolecular compounds, are expected to find applications in functional materials due to their high degree of freedom. However, their synthesis requires multistep reactions, and there is a demand for more convenient methods to synthesize rotaxane materials. In this study, we aimed to investigate a simpler method for synthesizing highly functional rotaxane materials and explore the diversity of molecular designs. To achieve this, we successfully synthesized a host–guest conjugated compound that incorporates both crown ether as the host unit and secondary ammonium salts as the guest unit within the same molecule. Subsequently, the metathesis reaction of these compounds, which construct [c2]daisy-chain rotaxanes, enabled the one-pot synthesis of a topological polymer called “poly([c2]daisy-chain rotaxane)” with a pseudo-stopper. This methodology achieves the stabilization and polymerization of rotaxanes simultaneously, contributing to the easy materialization of rotaxanes. Furthermore, the thiol-ene reaction achieved the extension of the distance between rotaxane units and provided a useful approach to diversify the design of functional materials with rotaxane structures. Full article

Nitrated products are important since they are intermediates in the synthesis of other compounds, such as explosives, perfumes, dyes and plastics, among others, and they have an easy capacity to convert into other functional groups. The synthesis of compounds with biological activity that have a nitro group in their structure is relevant to improving and/or enhancing their effect. In this work, different methodologies for the nitration of naphthoquinone derivative compounds are presented. The nitration of 3-R-2-(phenylamino)-1,4-naphthoquinone derivatives was carried out with nitric acid and sulfuric acid; milder reaction conditions were also established by diluting the acids or performing the reaction with weaker acids. Other methodologies were tested using nitrate salts for mononitrate product synthesis. We used a solvent-free reaction with oxalic acid using 3-R-2-(phenylamino)-1,4-naphthoquinones (R=H, Br or Cl), noting that the electronegativity of the chlorine group is decisive for achieving nitration with good yields. Finally, a Michael addition was performed with some nitrated anilines. To obtain denitrated compounds in the ortho and para positions, the reaction with strong acids is feasible; however, for the formation of mononitrated products, the Michael-type addition is more convenient. Full article

The effect of the different supports and catalyst-reducing agents on the Fischer–Tropsch (FT) reaction was investigated. The large surface area SiO₂ support with a smaller pore volume deposited fine, evenly distributed Co₃O₄. Cubic-shaped Co₃O₄ appeared in clusters on the TiO₂ support, whereas Co₃O₄ existed as single large particles on the Al₂O₃ support. The activity data obtained were discussed in terms of cluster size, particle size, particle shape, and mass transport limitations. The SiO₂-supported catalysts showed a higher activity for the formation of paraffinic products when reduced in H₂ at 250 °C. This is attributed to the formation of the CoO-Co active bond, which enhanced the activation of CO and the hydrogenation reactions. A higher activity was observed for the TiO₂-supported catalyst at a higher reduction temperature (350 °C) when the mass of Co metal was higher. It afforded more paraffinic products due to enhanced secondary hydrogenation of olefins at higher reaction rates. The large Co₃O₄ supported on Al₂O₃ showed the least activity at both reduction temperatures due to strong metal-support interactions. The H₂-reduced catalysts exhibited superior activity compared to all the syngas-reduced catalysts. Syngas reduction led to surface carbon deposition and the formation of surface carbides which suppressed the hydrogenation reactions and are selective to olefinic products. Full article

A literature review was conducted to examine the current understanding of the kinetics and mechanism of electrochemical reactions occurring during the electrodeposition of chromium coatings from electrolytes based on trivalent chromium compounds. The research in this scientific field is crucial, as it addresses the pressing need for an alternative to chromium plating processes that rely on solutions containing highly toxic and harmful hexavalent chromium compounds. Numerous literature data on the kinetics and mechanism of the stepwise reduction process of Cr(III) complex ions were analyzed. The influence of various additives and surfactants on the reaction kinetics of the stepwise reduction of trivalent chromium ions was considered. Special attention was given to the kinetics of the stepwise discharge of trivalent chromium ions in ionic liquids and deep eutectic solvents. Full article

During high-temperature pulse pyrolysis of acyclic butanes and pentanes under adiabatic compression conditions, cyclopropane, a stressed cyclic hydrocarbon, was found among the reaction products in small quantities for the first time. The analysis of the reaction products was performed by gas chromatography using three capillary columns of different polarity, selectivity and sufficient efficiency. The identification of reaction products, including cyclopropane, was performed using retention times of individual substances and model mixtures, as well as comparing chromatograms with reference chromatograms from the literature and the ScanView Application Database. It was shown that the chromatographic peak attributed to cyclopropane could not be a ghost peak. Additional confirmation of this conclusion was obtained in a series of experiments on the pyrolysis of n-butane at a reduced initial temperature of the adiabatic compression reactor (from 120 °C to 50 °C) and a modified mode of GC analysis. Cyclopropane yields as a function of maximum temperature have a bell-shaped asymmetric dependence. The maximum value of the yield of cyclopropane increases with the transition from normal alkanes to isoalkanes, and from pentanes to butanes; for n-pentane, 0.009 wt. %, and for isobutene, ≈0.017 wt. %. During the pulse pyrolysis of isobutane, n-butane, isopentane and n-pentane, cyclopropane is not a primary product. Further theoretical and experimental studies are needed to establish the mechanism of cyclopropane formation during pyrolysis of C₄–C₅ acyclic alkanes. Full article

The review is dedicated to the topical field of research aimed at creating catalysts combining several types of active sites. At the same time, the composition of Fischer–Tropsch synthesis (FTS) products can be controlled by changing the strength and concentration of the active sites and inter-site distances. A comparative analysis of the literature data allows to formulate the main principles of catalytic particles formation active in FTS and acid-catalyzed transformations of hydrocarbons: (1) the presence of weak Bronsted acid sites to control the cracking depth, (2) an availability of Bronsted acid sites for re-adsorption hydrocarbons and (3) weak Co-zeolite interaction to reduce methane formation. Full article

Water pollution by contaminants such as toxic metals and dyes is now a major concern due to their high toxicity and persistence in the environment. Advances in nanotechnology have enabled the use of micro/nanomaterials to treat and purify water in various industries. In this study, Bijoypur clay was modified with ethyldiamine and incorporated into an okra fiber (Abelmoschus esculentus) micro-cellulose crystal (MCC) to produce a composite that could absorb copper (Cu), nickel (Ni), and dyes like basic yellow (II) from industrial wastewater. Composites were prepared using different percentages of MCC and clay. Atomic absorption spectroscopy (AAS) was used to determine the concentrations of Cu and Ni whereas a UV–Visible spectrophotometer measured the absorbance of basic yellow (II). The synthesized composites were extensively characterized using a range of techniques including thermogravimetry (TG) and differential thermogravimetry (DTG), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Results show that both the MCC and clay could absorb Cu, Ni, and basic yellow (II) from the contaminated wastewater. The MCC and clay composite showed the maximum efficiency of metals removal, which was up to 95% (24 mg/g) for Cu at pH 6, 20 min contact time, 2 g/L adsorbent dose, and 100% (31 mg/g) for Ni at pH 8, 60 min contact time, and 2 g/L adsorbent dose, respectively, at the initial concentration of 50 mg/L. The maximum dye uptake capacity of 85% (19 mg/g) was observed by the MCC and clay composite under optimized conditions at the initial concentration of 50 mg/L, pH 8, 30 min contact time, and 1 g/L adsorbent dose compared to the pure clay, which had an efficiency up to 26% for Cu and 24% for dye removal. All of the results indicate that incorporating clay into MCC increases the absorption capacity of contaminants from wastewater, which could be more effective for environmental applications compared to untreated cellulose. Full article

We hereby describe an efficient method for the preparation of a series of new 1-substituted 1,2,3-triazole-based acetaminophen derivatives through a clean, good-yielding, simple, and expeditious procedure based on the O-propargylation reaction of the acetaminophen (APAP) obtained from expired commercial tablets and the CuBr(PPh₃)₃-catalyzed Huisgen reaction between O-propargylated APAP and diverse organoazides prepared from commercially available anilines as available starting reagents. An interesting nitric oxide-releasing 1,2,3-triazole hybrid of APAP was also obtained easily using the developed method. The structures of the designed hybrid compounds, which are expected to be pharmacologically active, were characterized by FT-IR, ¹H-, and ¹³C-NMR and are reported for the first time. According to the in-silico ADMET prediction studies performed in this work and literature analysis, these hybrids are interesting models in search of new pharmacological nontoxic agents endowed with anti-inflammatory and anticancer properties. Full article

Cellulases are a class of enzymes of great industrial interest that present several strategic applications. However, the high cost of enzyme production, coupled with the instabilities and complexities of proteins required for hydrolytic processes, still limits their use in several protocols. Therefore, enzyme immobilization may be an essential tool to overcome these issues. The present work aimed to evaluate the immobilization of cellulolytic enzymes of the commercial enzyme cocktail Celluclast^® 1.5 L in comparison to the cellulolytic enzyme cocktail produced from the wild strain Trichoderma harzianum I14-12 in Accurel^® MP1000. Among the variables studied were temperature at 40 °C, ionic strength of 50 mM, and 72 h of immobilization, with 15 m·L ⁻¹ of proteins generated biocatalysts with high immobilization efficiencies (87% for ACC-Celluclast biocatalyst and 95% for ACC-ThI1412 biocatalyst), high retention of activity, and specific activities in the support for CMCase (DNS method), FPase (filter paper method) and β-glucosidase (p-nitrophenyl-β-D-glucopyranoside method). Presenting a lower protein concentration (0.32 m·L⁻¹) than the commercial Celluclast^® 1.5 L preparation (45 m·L⁻¹), the ACC-ThI1412-derived immobilized biocatalyst showed thermal stability at temperatures higher than 60 °C, maintaining more than 90% of the residual activities of FPase, CMCase, and β-glucosidase. In contrast, the commercial-free enzyme presented a maximum catalytic activity at only 40 °C. Moreover, the difference in molecular weight between the component enzymes of the extract was responsible for different hydrophobic and lodging interactions of proteins on the support, generating a robust and competitive biocatalyst. Full article

The modern society produces large amounts of household waste with high organic matter content. The vermicomposting of household waste produces high-value humic substances and is a way to stabilize organic material for later use as raw material (3rd generation biomass) for bioenergy proposes. A 6-month matured compost, combining vegetable and fruit scraps from domestic trash and grass and shrub clippings from yard waste, was evaluated to assess its potential as a raw material in pyrolysis processes. The pyrolysis activation energy (Kissinger) of the composted material showed values in the range of 200–300 kJ/mol, thus confirming its suitability for pyrolysis processes with promising H₂ yields. The treatment of the composted material with H₂SO₄ and NaOH solution (boiling; 1 mol/L) led to the production of solid residues that present higher pyrolysis activation energies, reaching 550 kJ/mol for the most resilient fraction, which makes them suitable to produce carbonaceous materials (biochar) that will have incorporated the inorganics existing in the original compost (ashes 37.6%). The high content of inorganics would play a chief role during pyrolysis since they act as gasification promoters. Full article

The resistance of bacteria to current antibiotic drugs and the re-occurrence of different ailments after several therapeutic protocols continue to be a cause for concern. Arylated amino acids are vital synthons to many compounds; they serve as essential building blocks in the synthesis of nitrogen heterocycles with various biological activities. This research reports on the synthesis of some N-aryl amino acids and evaluates their antibacterial activities. The N-aryl amino acids 3a–3j were obtained by reacting different 4-substituted fluorobenzene 1a–1d with different amino acids 2a–2g via a metal-free base-induced aryl amination reaction of aryl halides. The antibacterial activities of the synthesized compounds were evaluated against eight bacterial strains (Four Gram-positive, Bacillus subtilis (ATCC 6633), Streptococcus pneumonia (ATCC 33400), Staphylococcus aureus (ATCC 25923), and Staphylococcus epidermidis (ATCC 14990), and four Gram-negative, Enterobacter cloacae (ATCC 43560), Escherichia coli (ATCC 25922), Proteus mirabilis (ATCC 43071), and Klebsiella oxytoca (ATCC 13182) using the agar well diffusion method with streptomycin as a reference drug. The biological screening indicates that the synthesized compounds 3a, 3e, and 3j have promising broad-spectrum antibacterial potential, as the N-aryl amino acid displayed activity that was comparable to the standard drug against Streptococcus pneumonia, Escherichia coli, and Proteus mirabilis. Full article

The Methionine Synthase process, in principle, can take an unlimited number of turnovers in the presence of the AdoMet substrate. In the absence of this substrate, the Methionine Synthase process lasts only about 2000 turnovers. During 2000 turnovers, the entire amount of methylcob(II)alamin cofactor is converted into inactive cob(II)alamin particles. Nevertheless, the mechanism of the Methionine Synthase process determined previously lacks the presence of the AdoMet substrate. On the other hand, the first step of this mechanism was only mentioned earlier without its analysis. The CASSCF geometry optimization of the inactive cob(II)alamin cofactor particle plus the AdoMet ion substrate and of the methylcob(II)alamin cofactor particle plus homocysteine ion and histidine molecule joint models have been performed. CASSCF calculations show that the AdoMet particle transfers the methyl radical to the biologically inactive cob(II)alamin particle during their interaction, transforming it into the biologically active particle of methylcob(II)alamin. CASSCF geometry optimization of the second model leads to the Co-N bond’s full cleavage. The two processes take place in the absence of the total energy barrier. The fully updated mechanism of the Methionine Synthase process has been drawn. Full article

The synthetic methods leading to furo[3,2-b]pyrroles and thiazolo [5,4-d]thiazoles are reviewed herein. Furo-, thieno- and seleno [3,2-b]pyrroles are related to heteropentalenes, containing two heteroatoms in the entire structure, one each per core. The synthetic approach follows the Hemetsberger–Knittel protocol covering three reaction steps—the nucleophilic substitution of halogen-containing aliphatic carboxylic acid esters, Knoevenagel condensation and, finally, thermolysis promoting the intramolecular cyclocondensation to O,N-heteropentalene. The Hemetsberger–Knittel reaction sequence is also known for the preparation of O,N-heteropentalenes with three heteroatoms (2:1) and their sulphur and selen heteroatoms containing structural analogues and bispyrroles. The synthetic approach towards thiazolo [5,4-d] thiazoles represents a more straightforward route, according to the Ketcham cyclocondensation. Proceeding with the Ketcham process is more challenging since it occurs stepwise and the formation of by-products is obvious. Thiazolo [5,4-d]thiazole is a representative of the aromatic heteropentalene with four heteroatoms in the structure—twinned N and S, two for each of the five-membered rings. The synthetic approaches towards those particular heteropentalnes have been chosen as a consequence of our ongoing research dealing with the design, synthesis and applications of substituted furo [3,2-b]pyrroles and thiazolo [5,4-d]thiazole-based derivatives. While the furopyrroles are known for their pharmacological activity, thiazolothiazoles have become of interest to materials science. We are aware that from a “bank” of existing compounds/procedures not all are presented in this review, and we apologise to respective groups whose research have not been objectively included. Full article

Photocatalysis application in water treatment has been the object of many researchers worldwide in recent decades. However, there are limited commercial applications due to low photon transfer efficiency, which create barriers leading to challenges in making the process efficient and economically feasible. Fixed UV/visible light sources, which are generally located outside the reactor or encapsulated in quartz tube inside the reactor are the source of energy to activate photocatalyst generating powerful oxidants such as electrons and holes. Suspended waterproof LED visible lights were employed to enhance photon transfer efficiency. Consequently, the required energy was lower resulting in negligible temperature increase and eliminated the need for an external cooler, no need for quartz (UV transparent) or treated glass reactors, enhanced mixing due to continuous movement of light bulbs by convective currents, and minimum/no attenuation. Direct Blue 15 (DB15) dye was used as model compound and the photocatalyst was P25 TiO₂ (Average particle: 30 nm, Surface area: 50 m² g⁻¹). The samples taken at different time intervals were analyzed by UV-Vis. spectrophotometer (UV-3600), and TOC-V CPN total organic carbon analyzer (both from Shimadzu). It was found that for the same level of degradation, the degradation rate increased by about 50% compared to conventional fixed light photoreactor. Overall, the cost of the operation can be reduced substantially, paving the road for feasible commercialization of the process. Full article

Partially purified alkaline protease produced by an indigenous bacterial strain, Bacillus aryabhattai Ab15-ES, was insolubilized in alginate beads using an entrapment technique. Maximum entrapped enzyme activities of 68.76% and 71.06% were recorded at optimum conditions of 2% (w/v) sodium alginate and 0.3 M calcium chloride. Biochemical profiling of free and immobilized proteases was investigated by determining their activity and stability as well as kinetic properties. Both enzyme preparations exhibited maximum activity at the optimum pH and temperature of 8.0 and 50 °C, respectively. However, in comparison to the free enzyme, the immobilized protease showed improved pH stability at 8.0–9.0 and thermal stability at 40–50 °C. In addition, the entrapped protease exhibited a higher Vmax and increased affinity to the substrate (1.65-fold) than the soluble enzyme. The immobilized protease was found to be more stable than the free enzyme, retaining 80.88% and 38.37% of its initial activity when stored at 4 °C and 25 °C, respectively, for 30 d. After repeated use seven times, the protease entrapped in alginate beads maintained 32.93% of its original activity. These findings suggest the efficacy and sustainability of the developed immobilized catalytic system for various biotechnological applications. Full article