Journal Description
Reactions
Reactions
is an international, peer-reviewed, open access journal on reaction chemistry and engineering published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within ESCI (Web of Science), Scopus, EBSCO, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 18.3 days after submission; acceptance to publication is undertaken in 3.9 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Modeling of the Anaerobic Digestion of Biomass Produced by Agricultural Residues in Greece
Reactions 2024, 5(2), 338-349; https://doi.org/10.3390/reactions5020017 - 22 May 2024
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This study combines theoretical modeling and experimental validation to explore anaerobic digestion comprehensively. Developing a computational model is crucial for accurately simulating a digester’s performance, considering various feedstocks and operational parameters. The main objective was to adapt the anaerobic digestion model 1 (ADM1)
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This study combines theoretical modeling and experimental validation to explore anaerobic digestion comprehensively. Developing a computational model is crucial for accurately simulating a digester’s performance, considering various feedstocks and operational parameters. The main objective was to adapt the anaerobic digestion model 1 (ADM1) simulation code to align with the laboratory-scale anaerobic digestion reactor’s specifications, especially regarding the liquid–gas transfer process. Within this computational framework, users may define model parameters and elucidate processes occurring in compartments reflecting the physical design. The model accurately predicts total concentrations of chemical oxygen demand (COD) as well as the produced biogas, with an average difference of less than 10% between experimental and simulated data. This consistency underscores the reliability and effectiveness of the adapted model in capturing anaerobic digestion nuances under specified conditions.
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Open AccessReview
Ir-Catalyzed ortho-C-H Borylation of Aromatic C(sp2)-H Bonds of Carbocyclic Compounds Assisted by N-Bearing Directing Groups
by
Hamad H. Al Mamari
Reactions 2024, 5(2), 318-337; https://doi.org/10.3390/reactions5020016 - 1 May 2024
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C-H borylation is a powerful strategy for the construction of C-B bonds due to the synthetic versatility of C-B bonds. Various transition metals affect the powerful functionalization of C-H bonds, of which Ir is the most common. Substrate-directed methods have enabled directed Ir-catalyzed
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C-H borylation is a powerful strategy for the construction of C-B bonds due to the synthetic versatility of C-B bonds. Various transition metals affect the powerful functionalization of C-H bonds, of which Ir is the most common. Substrate-directed methods have enabled directed Ir-catalyzed C-H borylation at the ortho position. Amongst the powerful directing groups in Ir-catalyzed C-H borylation are N-containing carbocyclic systems. This review covers substrate-directed Ir-catalyzed ortho-C-H borylation of aromatic C(sp2)-H bonds in N-containing carbocyclic compounds, such as anilines, amides, benzyl amines, hydrazones, and triazines.
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Open AccessArticle
Generalized Linear Driving Force Formulas for Diffusion and Reaction in Porous Catalysts
by
Mirosław K. Szukiewicz and Elżbieta Chmiel-Szukiewicz
Reactions 2024, 5(2), 305-317; https://doi.org/10.3390/reactions5020015 - 29 Apr 2024
Abstract
Approximate models are a fast and most often precise tool for determining the effectiveness factor for heterogeneous catalysis processes that are realized in the real world. They are also frequently applied as robust transient models describing the work of a single catalyst pellet
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Approximate models are a fast and most often precise tool for determining the effectiveness factor for heterogeneous catalysis processes that are realized in the real world. They are also frequently applied as robust transient models describing the work of a single catalyst pellet or as a part of a more complex model, for example, a reactor model, where mass balances for the gas phase and solid phase are necessary. So far, approximate models for diffusion and reaction processes have been presented for processes described by a single balance equation. In the present work, approximate models without the mentioned limitation are presented and discussed. In addition, simple rules are shown for the development of other complex approximate models without tedious derivation in the complex domain. The formulas considered in this work are typical long-time approximations of the transient process. The accuracy is good, especially in the range of small and intermediate Thiele modulus values.
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(This article belongs to the Special Issue Feature Papers in Reactions in 2024)
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Open AccessArticle
Sewage Sludge Plasma Gasification: Characterization and Experimental Rig Design
by
Nuno Pacheco, André Ribeiro, Filinto Oliveira, Filipe Pereira, L. Marques, José C. Teixeira, Cândida Vilarinho and Flavia V. Barbosa
Reactions 2024, 5(2), 285-304; https://doi.org/10.3390/reactions5020014 - 16 Apr 2024
Abstract
The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater
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The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater treatment (WWT) sewage sludge through plasma gasification. Effective syngas production hinges on precise equipment design which, in turn, depends on the detailed feedstock used for characterization. Key components of plasma gasification include the plasma torch, reactor, heat exchanger, scrubber, and cyclone, enabling the generation of inert slag for landfill disposal and to ensure clean syngas. Designing these components entails considerations of sludge composition, calorific power, thermal conductivity, ash diameter, and fusibility properties, among other parameters. Accordingly, this work entails the development of an experimental setup for the plasma gasification of sewage sludge, taking into account a comprehensive sludge characterization. The experimental findings reveal that domestic WWT sewage sludge with 40% humidity exhibits a low thermal conductivity of approximately 0.392 W/mK and a calorific value of LHV = 20.78 MJ/kg. Also, the relatively low ash content (17%) renders this raw material advantageous for plasma gasification processes. The integration of a detailed sludge characterization into the equipment design lays the foundation for efficient syngas production. This study aims to contribute to advancing sustainable waste-to-energy technologies, namely plasma gasification, by leveraging sewage sludge as a valuable resource for syngas production.
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(This article belongs to the Special Issue Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes)
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Open AccessArticle
Biosynthesis of Copper Nanoparticles from Acacia cornigera and Annona purpurea and Their Insecticidal Effect against Tribolium castaneum
by
Rogelio Solorzano Toala, Federico Gutierrez-Miceli, Benjamin Valdez-Salas, Ernesto Beltran-Partida, Daniel Gonzalez-Mendoza, Olivia Tzintzun-Camacho, Onecimo Grimaldo-Juarez and Antobelli Basilio-Cortes
Reactions 2024, 5(2), 274-284; https://doi.org/10.3390/reactions5020013 - 8 Apr 2024
Abstract
Diverse studies have showed that the pesticides can cause important damages in ecosystem. Therefore, the development of bio pesticides through nanotechnology can increase efficacy and limit the negative impacts in the environmental that traditionally seen through the use of chemical pesticides. Nanoparticles obtained
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Diverse studies have showed that the pesticides can cause important damages in ecosystem. Therefore, the development of bio pesticides through nanotechnology can increase efficacy and limit the negative impacts in the environmental that traditionally seen through the use of chemical pesticides. Nanoparticles obtained from plants’ extracts can be used for effective pest management as a combined formulation of metal and some other organic material present in the plants. In the present study, our evaluated biosynthesis of nanoparticles of copper used two plant extracts (Acacia cornigera and Annona purpurea), and the Taguchi method was adopted for the synthesis optimization of the following variables of biosynthesis: temperature, pH, extract concentration, and reaction times to maximize the insecticidal activity on Tribolium castaneum. Our results showed that the nanoparticles were successfully synthesized using Acacia cornigera and Anona purpurea extract under optimum conditions under Taguchi L 9 orthogonal design, where copper nanoparticles were obtained with a size of 63–153 nm for using A. cornigera extract, 87–193 nm for A. purpurea extract, and a zeta potential of 9.6 mV and −32.7 mV, respectively. The nanoparticles of copper from A. cornigera showed effective insecticidal activity against Tribolium castaneum, and 90% mortality compared to the 76.6% obtained from nanoparticles of copper from A. purpurea. The results suggest that Cu-nanoparticles derived from both plants could be used as a biocontrol agent of Tribolium castaneum, a pest of stored grain with great economic importance.
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(This article belongs to the Special Issue Nanoparticles: Synthesis, Properties, and Applications)
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Open AccessArticle
Valorization of (Bio)Ethanol over MoO3/(WO3-ZrO2) Sol-Gel-like Catalysts
by
Ana Paula Soares Dias, Bruna Rijo, Manuel Francisco Costa Pereira, Rodica Zăvoianu and Octavian Dumitru Pavel
Reactions 2024, 5(1), 260-273; https://doi.org/10.3390/reactions5010012 - 20 Mar 2024
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Bioethanol, which is currently produced commercially from a growing variety of renewable biomass and waste sources, is an appealing feedstock for the production of fuels and chemicals. The literature clearly shows that bioethanol is a versatile building block to be used in biorefineries.
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Bioethanol, which is currently produced commercially from a growing variety of renewable biomass and waste sources, is an appealing feedstock for the production of fuels and chemicals. The literature clearly shows that bioethanol is a versatile building block to be used in biorefineries. The ethanol conversion using several catalysts with acidic, basic, and redox characteristics results in a diverse assortment of high-value bioproducts. High-acidity tungsten zirconia-based catalysts are stated to compete with traditional zeolitic catalysts and can be employed in the dehydration of ethanol to ethylene, but for a low reaction temperature acetic acid is formed, which causes corrosion issues. WO3-ZrO2 (W/Zr = 1, atomic) catalysts modified with MoO3 were prepared by a sol-gel-like procedure and tested in a gas phase ethanol conversion in the presence of air. The citrate derived xerogels were annealed at 853 K for 12 h, allowing low surface area (<10 m2/g) materials with a Mo-W mixed-oxide-rich surface over tetragonal nanostructured zirconia. Catalysts with MoO3-loading produced mainly acetaldehyde, instead of ethylene, as a result of the high reducibility of Mo6+ when compared to W6+. During the reaction, the Mo6+ becomes partially reduced, but Mo6+/Mo5+ species are still active for methanol conversion with increased ethylene selectivity due to the high acidity of tetrahedral MOX species formed during the reaction. Adding water to ethanol, to simulate bioethanol, only leads to a slight inhibition in ethanol conversion over the MoO3/(WO3-ZrO2) catalysts. The results show that molybdenum oxide deposited on tungstated zirconia catalyst is active, with low sensitivity to water, for the valorization of bioethanol into high-value chemicals, such as ethylene and acetaldehyde, and whose selectivity can be tuned by changing the amount of MoO3 that is loaded. The MoO3/(WO3-ZrO2) catalysts prepared show catalytic behavior similar to that of noble metal-based catalysts reported in the literature for the dehydrogenation of bioethanol in high-value chemicals.
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Open AccessArticle
Analytical and Numerical Thermodynamic Equilibrium Simulations of Steam Methane Reforming: A Comparison Study
by
Bruno Varandas, Miguel Oliveira and Amadeu Borges
Reactions 2024, 5(1), 246-259; https://doi.org/10.3390/reactions5010011 - 8 Mar 2024
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Computer simulation is a crucial element in the design of chemical processes. Although numerous commercial software options are widely recognized, the expense associated with acquiring and sustaining valid software licenses can be prohibitive. In contrast, open-source software, being freely available, provides an opportunity
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Computer simulation is a crucial element in the design of chemical processes. Although numerous commercial software options are widely recognized, the expense associated with acquiring and sustaining valid software licenses can be prohibitive. In contrast, open-source software, being freely available, provides an opportunity for individuals to study, review, and modify simulation models. This accessibility fosters technology transfer and facilitates knowledge dissemination, benefiting both academic and industrial domains. In this study, a thermodynamic equilibrium steady-state analysis of steam methane reforming using a natural-gas-like intake fuel was conducted. An analytical method was developed on the Microsoft Excel platform, utilizing the material balance equations system. The obtained results were compared to numerical methods employing the free-of-charge chemical process simulation software COCO and DWSIM. The investigation explored the influence of temperature, pressure, and steam-to-carbon ratio to determine optimal operating conditions. The findings suggest that higher temperatures and lower pressures are highly favorable for this process, considering that the choice of steam-to-carbon ratio depends on the desired conversion, with a potential disadvantage of coke formation at lower values. Consistent results were obtained through both analytical and numerical methods. Notably, simulations performed using DWSIM showed a deviation of 6.42% on average compared to COCO values. However, it was observed that the analytical method tended to overestimate the results by an average of 3.01% when compared to the simulated results from COCO, highlighting the limitations of this analytical approach.
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Open AccessReview
Bioorthogonal “Click” Cycloadditions: A Toolkit for Modulating Polymers and Nanostructures in Living Systems
by
Irene Lepori, Yavuz Oz, Jungkyun Im, Nandan Ghosh, Mohuya Paul, Ulrich S. Schubert and Stefano Fedeli
Reactions 2024, 5(1), 231-245; https://doi.org/10.3390/reactions5010010 - 4 Mar 2024
Abstract
“Click” cycloadditions offer effective pathways for the modifications of supramolecular structures, polymers, and nanomaterials. These reactions include bioorthogonal mechanisms that do not interfere with the biological processes, providing a type of chemistry to operate directly in living environments, such as cells and animals.
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“Click” cycloadditions offer effective pathways for the modifications of supramolecular structures, polymers, and nanomaterials. These reactions include bioorthogonal mechanisms that do not interfere with the biological processes, providing a type of chemistry to operate directly in living environments, such as cells and animals. As a result, the “click” cycloadditions represent highly and selective tools for tailoring the properties of nanomedicine scaffolds, expanding the efficacy of multiple therapeutic strategies. We focused this minireview on the bioorthogonal cycloadditions, presenting an insight into the strategies to modify nanostructured biomedical scaffolds inside living systems. We organized the contributions according to the three main mechanisms of “click” cycloadditions: strain-promoted sydnone-alkyne, tetrazine ligation, and strain-promoted [3+2] azido-alkyne.
Full article
(This article belongs to the Special Issue Cycloaddition Reactions at the Beginning of the Second Millennium)
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Open AccessArticle
Reduction and Cycloaddition of Heteroalkenes at Ga(I) Bisamide Center
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Vladimir A. Dodonov, Olga A. Kushnerova, Evgeny V. Baranov and Igor L. Fedushkin
Reactions 2024, 5(1), 213-230; https://doi.org/10.3390/reactions5010009 - 20 Feb 2024
Abstract
The reactivity of the complex [(dpp-bian)GaNa(DME)2] (1) (dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) towards isocyanates, benzophenone, diphenylketene, and 1,2-dibenzylidenehydrazine has been studied. Treatment of 1 with isocyanates led to derivatives of imidoformamide [(dpp-bian)Ga{C(=NPh)2}2–NPh][Na(DME)3] (2),
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The reactivity of the complex [(dpp-bian)GaNa(DME)2] (1) (dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) towards isocyanates, benzophenone, diphenylketene, and 1,2-dibenzylidenehydrazine has been studied. Treatment of 1 with isocyanates led to derivatives of imidoformamide [(dpp-bian)Ga{C(=NPh)2}2–NPh][Na(DME)3] (2), biuret [(dpp-bian)Ga(NCy)2(CO)2NCy][Na(DME)] (3), or carbamic acids [(dpp-bian)GaN(Cy)C(O)O]2[Na(THF)(Et2O)] (4), [(dpp-bian)GaC(=NCy)N(Cy)C(O)O][Na(Py)3] (5). Treatment of 1 with 2 equiv. of Ph2CO resulted in gallium pinacolate [(dpp-bian)GaO(CPh2)2O][Na(Py)2] (9), while the reaction of 1 with 2 equiv. Ph2CCO gave divinyl ether derivative [(dpp-bian)Ga{C(=CPh2)O}2][Na(DME)3] (10). Complex 1 treated with 2 equiv. 1,2-dibenzylidenehydrazine underwent [1+2+2] cycloaddition to give C–C coupling product [(dpp-bian)Ga{N(NCHPh)}2(CHPh)2][Na(DME)3] (11). When complex 1 was sequentially treated with 1 equiv. of 1,2-dibenzylidenehydrazine and 1 equiv. of pyridine or pyridine-d5; it gave [1+2+2] cycloaddition product [(dpp-bian)GaN(NCHPh)C(Ph)CN][Na(DME)3] (12). Compounds 2–12 were characterized by NMR and IR spectroscopy, and their molecular structures were established by single-crystal X-ray diffraction analysis.
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(This article belongs to the Special Issue Cycloaddition Reactions at the Beginning of the Second Millennium)
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Open AccessReview
Use of Biosourced Molecules as Liquid Organic Hydrogen Carriers (LOHC) and for Circular Storage
by
Nelson Alexis Bermudez Aponte and Valérie Meille
Reactions 2024, 5(1), 195-212; https://doi.org/10.3390/reactions5010008 - 7 Feb 2024
Abstract
The use of Liquid Organic Hydrogen Carriers (LOHC) is one of the potential options to store hydrogen. Today, the vast majority of compounds used as LOHC come from the oil industry. Using biosourced LOHC would be a step forward in the development of
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The use of Liquid Organic Hydrogen Carriers (LOHC) is one of the potential options to store hydrogen. Today, the vast majority of compounds used as LOHC come from the oil industry. Using biosourced LOHC would be a step forward in the development of this CO2-free solution. This article looks at LOHC candidates that can be obtained from biomass. The special case of formic acid and methanol, which do not fall within the definition of LOHC, is also considered. The synthesis of alcohols, polyols, amines, aminoalcohols and N-heterocyclic compounds from biosourced compounds is reviewed.
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(This article belongs to the Special Issue Hydrogen Production and Storage, 2nd Edition)
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Open AccessReview
Photocatalytic TiO2-Based Nanostructures as a Promising Material for Diverse Environmental Applications: A Review
by
Maria-Anna Gatou, Athanasia Syrrakou, Nefeli Lagopati and Evangelia A. Pavlatou
Reactions 2024, 5(1), 135-194; https://doi.org/10.3390/reactions5010007 - 1 Feb 2024
Cited by 1
Abstract
Contemporary technological and industrial advancements have led to increased reliance on chemicals for product innovation, leading to heightened contamination of water sources by traditional pollutants (organic dyes, heavy metals) and disease-causing microorganisms. Wastewater treatment processes now reveal “emerging pollutants”, including pharmaceuticals, endocrine disruptors,
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Contemporary technological and industrial advancements have led to increased reliance on chemicals for product innovation, leading to heightened contamination of water sources by traditional pollutants (organic dyes, heavy metals) and disease-causing microorganisms. Wastewater treatment processes now reveal “emerging pollutants”, including pharmaceuticals, endocrine disruptors, and agricultural chemicals. While some are benign, certain emerging pollutants can harm diverse organisms. Researchers seek cost-effective water purification methods that completely degrade pollutants without generating harmful by-products. Semiconductor-based photocatalytic degradation, particularly using titanium dioxide (TiO2), is popular for addressing water pollution. This study focuses on recent applications of TiO2 nanostructures in photocatalysis for eliminating various water pollutants. Structural modifications, like doping and nanocomposite formation, enhance photocatalyst performance. The study emphasizes photocatalytic elimination mechanisms and comprehensively discusses factors impacting both the mechanism and performance of nano-TiO2-based photocatalysts. Characteristics of TiO2, such as crystal structure and energy band-gap, along with its photocatalytic activity mechanism, are presented. The review covers the advantages and limitations of different TiO2 nanostructure production approaches and addresses potential toxicity to human health and the environment. In summary, this review provides a holistic perspective on applying nano-TiO2 materials to mitigate water pollution.
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(This article belongs to the Special Issue Nanoparticles: Synthesis, Properties, and Applications)
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Open AccessArticle
Oxidative Cleavage of 9,10-Dihydroxystearic Acid on Supported Au, Pd and PdAu Nanoparticle-Based Catalysts
by
Dmitrii German, Vladislav Turyanskiy, Julia Schroeder, Mohammed Al-Yusufi, Katja Neubauer, Angela Köckritz, Sónia A. C. Carabineiro, Ekaterina Kolobova and Alexey Pestryakov
Reactions 2024, 5(1), 120-134; https://doi.org/10.3390/reactions5010006 - 27 Jan 2024
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The oxidative C-C cleavage of a C18 substrate is an important transformation in synthetic organic chemistry, facilitating the synthesis of valuable C8-C9 acids widely used in many industries. Through a comparative analysis of the catalytic and physicochemical properties of
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The oxidative C-C cleavage of a C18 substrate is an important transformation in synthetic organic chemistry, facilitating the synthesis of valuable C8-C9 acids widely used in many industries. Through a comparative analysis of the catalytic and physicochemical properties of catalysts, comprising mono- (Pd or Au) and bimetallic (PdAu) nanoparticles deposited on oxides, oxyhydroxides and graphite-like carbon material Sibunit (Cp), it was shown that the efficiency of the catalyst in the oxidative cleavage of 9,10-dihydroxystearic acid relies on the nature of the active component, the support and the average size of metal nanoparticles (NPs). The dependency of 9,10-DSA conversion on the average size of metal NPs shows the structural sensitivity of the oxidative cleavage reaction. Notably, catalysts with an average size of gold particles less than 3 nm exhibit the highest activity. The nature of the active component and the support material are crucial factors determining the process selectivity. Among the catalysts studied, the most effective for the oxidative cleavage of 9,10-DSA is a material based on Au NPs deposited on Cp.
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Open AccessBrief Report
Preparation of Dibenzofurotropones via Pd-Catalyzed Cyclization
by
Yu-Wei Lin and Shiuh-Tzung Liu
Reactions 2024, 5(1), 111-119; https://doi.org/10.3390/reactions5010005 - 22 Jan 2024
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A synthetic approach to dibenzofurotropone derivatives 1 has been developed through the palladium-catalyzed cyclization of (2-bromoaryl)(3-arylfuran-2-yl)methanones 2 via the activation of arylic C–H bonds. Compounds 2 were easily prepared from the palladium-promoted acyl migration and cyclization of (Z)-pent-2-en-4-yn-1-yl acetates 3 in
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A synthetic approach to dibenzofurotropone derivatives 1 has been developed through the palladium-catalyzed cyclization of (2-bromoaryl)(3-arylfuran-2-yl)methanones 2 via the activation of arylic C–H bonds. Compounds 2 were easily prepared from the palladium-promoted acyl migration and cyclization of (Z)-pent-2-en-4-yn-1-yl acetates 3 in the presence of 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU), followed by oxidative decarbonylation and oxidation with O2. Ten new tropone compounds are reported and these compounds show absorption in the UV-vis region and emission in the visible region.
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Open AccessArticle
Formation of OH Radicals on BiVO4–TiO2 Nanocomposite Photocatalytic Film under Visible-Light Irradiation: Roles of Photocatalytic Reduction Channels
by
Shizu Terao and Yoshinori Murakami
Reactions 2024, 5(1), 98-110; https://doi.org/10.3390/reactions5010004 - 22 Jan 2024
Abstract
In this study, we investigated the effects of H2O2 addition on OH radical formation on the surfaces of visible-light-irradiated BiVO4–TiO2 nanocomposite photocatalysts. Additionally, we examined the possible roles of OH radicals formed by the reduction reaction of
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In this study, we investigated the effects of H2O2 addition on OH radical formation on the surfaces of visible-light-irradiated BiVO4–TiO2 nanocomposite photocatalysts. Additionally, we examined the possible roles of OH radicals formed by the reduction reaction of H2O2 on the visible-light-irradiated surfaces of photocatalytic BiVO4–TiO2 nanocomposites. The BiVO4–TiO2 nanocomposite photocatalysts were prepared by mixing a BiVO4 photocatalytic film with commercially available semiconductor particulate TiO2 photocatalysts. By removing oxygen gas from the photocatalytic reactor, the effects of oxygen molecules on OH radical formation during the visible-light irradiation of BiVO4–TiO2 nanocomposite photocatalysts were examined. During visible-light irradiation, BiVO4 and BiVO4–TiO2 photocatalysts play different roles in OH radical formation because of two characteristic reduction reaction channels: (a) the direct reduction of H2O2 on photocatalytic surfaces and (b) the indirect reduction reaction of H2O2 by superoxide radical anions (O2−).
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(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
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Dry and Hydrothermal Co-Carbonization of Mixed Refuse-Derived Fuel (RDF) for Solid Fuel Production
by
Andrei Longo, Octávio Alves, Ali Umut Sen, Catarina Nobre, Paulo Brito and Margarida Gonçalves
Reactions 2024, 5(1), 77-97; https://doi.org/10.3390/reactions5010003 - 16 Jan 2024
Abstract
The present study aims to test several conditions of the thermochemical pretreatment of torrefaction and carbonization to improve the physical and combustible properties of the Portuguese RDF. Therefore, two different types of RDF were submitted alone or mixed in 25%, 50%, and 75%
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The present study aims to test several conditions of the thermochemical pretreatment of torrefaction and carbonization to improve the physical and combustible properties of the Portuguese RDF. Therefore, two different types of RDF were submitted alone or mixed in 25%, 50%, and 75% proportions to dry carbonization processes in a range of temperatures between 250 to 350 °C and residence time between 15 and 60 min. Hydrothermal carbonization was also carried out with RDF samples and their 50% mixture at temperatures of 250 and 300 °C for 30 min. The properties of the 51 chars and hydrochars produced were analyzed. Mass yield, apparent density, proximate and elemental analysis, ash mineral composition, and higher heating value (HHV), among others, were determined to evaluate the combustion behavior improvement of the chars. The results show that after carbonization, the homogeneity and apparent density of the chars were increased compared to the raw RDF wastes. The chars and hydrochars produced present higher HHV and lower moisture and chlorine content. In the case of chars, a washing step seems to be essential to reduce the chlorine content to allow them to be used as an alternative fuel. In conclusion, both dry and wet carbonization demonstrated to be important pretreatments of the RDF to produce chars with improved physical and combustion properties.
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(This article belongs to the Special Issue Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes)
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Open AccessReview
The Miracle of Vitamin B12 Biochemistry
by
Tudor Spataru
Reactions 2024, 5(1), 20-76; https://doi.org/10.3390/reactions5010002 - 5 Jan 2024
Abstract
For decades, the comparison of experimental data with theoretical results in studying the biochemistry of vitamin B12 has been very confusing. While the methylcobalamin cofactor-dependent Methionine Synthase process can undergo unlimited turnovers, and some of the adenosylcobalamin-dependent processes run with close-to-unity equilibrium constants
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For decades, the comparison of experimental data with theoretical results in studying the biochemistry of vitamin B12 has been very confusing. While the methylcobalamin cofactor-dependent Methionine Synthase process can undergo unlimited turnovers, and some of the adenosylcobalamin-dependent processes run with close-to-unity equilibrium constants (e.g., with close-to-zero energy barriers), the DFT and QM/MM based on density functional theory, the most used and appreciated methods for calculating the electronic structure of molecules, have been showing a much shorter than experimental-determined Co-N distances in the vitamin B12 cofactors of Co+2 and the inadequate large energetic barriers of their enzymology bioprocesses. The confusion was even larger since some in vitro experimental data showed large barriers to the vitamin B12 cofactor reactions (which in fact play a destructive role in the Methionine Synthase process and which barriers were caused mostly by the influence of the solvents in which the reaction took place). It reached the point where solid contributions to the study of the biochemical processes of vitamin B12 were almost officially questioning the correctness of the experimental determination of the Co-N chemical bond distances in the cobalt(II) cofactors of vitamin B12. Unexpectedly, all the theoretical biochemistry of the vitamin B12 cofactors began to agree with all in vivo experimental data only when they were treated with the MCSCF method, the method that considers the orbital mixing, or in other words, the Pseudo-Jahn–Teller Effect. MCSCF data establish unknown mechanistic details of the methyl radical and hydrogen transfers, the origin of the electronic transfers between bioreagents, and the nature and the relationship between the bioreactions. The Pseudo-Jahn–Teller Effect, e.g., orbital mixing, governs vitamin B12 chemistry in general and provides insight into particular details of vitamin B12-dependent reactions in the human body. It turns out that the DFT or QM/MM based on DFT method theoretical data are incongruent with the experimental data due to their limitations, e.g., the unaccounted-for effects of orbital mixing.
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(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
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Open AccessReview
A Critical Review of the Sustainable Production and Application of Methanol as a Biochemical and Bioenergy Carrier
by
Arash Yahyazadeh, Sonil Nanda and Ajay K. Dalai
Reactions 2024, 5(1), 1-19; https://doi.org/10.3390/reactions5010001 - 27 Dec 2023
Cited by 2
Abstract
There is a growing interest in the production of biofuels and biochemicals from renewable biomass. Biomass in the form of woody and agricultural residues, municipal solid waste and other organic refuse is becoming popular as a feedstock for biofuel and biochemical production through
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There is a growing interest in the production of biofuels and biochemicals from renewable biomass. Biomass in the form of woody and agricultural residues, municipal solid waste and other organic refuse is becoming popular as a feedstock for biofuel and biochemical production through thermochemical and biological routes. Methanol, a widely used industrial chemical, also has clean fuel properties due to its high-octane number, low flammability, low emissions and high engine performance. This paper performs a comprehensive review of different thermochemical and biological processes able to sustainably convert waste biomass to methanol. This article also evaluates the techno-economic assessment and lifecycle analysis of different processes used for methanol production. The article discusses the effects of process parameters and biomass properties on methanol production and utilization. Finally, the article concludes with recommendations on the eco-friendly aspects of methanol for use as a clean fuel and chemical derived from renewable organic bioresources.
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(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
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Open AccessCommunication
Increased Yields of the Guanine Oxidative Damage Product Imidazolone Following Exposure to LED Light
by
Taishu Kawada, Moka Maehara and Katsuhito Kino
Reactions 2023, 4(4), 801-810; https://doi.org/10.3390/reactions4040046 - 16 Dec 2023
Abstract
Among the bases of DNA, guanine is the most easily oxidized. Imidazolone (Iz) is a guanine oxidative damage, and we sought to generate Iz-containing oligomers. In this paper, we describe the methods and conditions to increase the yield of Iz by employing photooxidation
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Among the bases of DNA, guanine is the most easily oxidized. Imidazolone (Iz) is a guanine oxidative damage, and we sought to generate Iz-containing oligomers. In this paper, we describe the methods and conditions to increase the yield of Iz by employing photooxidation reactions using light-emitting diodes (LEDs) with emission wavelengths of 365 nm and 450 nm. For photooxidation performed with the 450 nm LED source at light intensities of 2.75–275 mW/cm2, peak yields of Iz were 35% at light intensities of 27.5 and 68.8 mW/cm2. For reactions performed with the 365 nm LED source at light intensities of 5.12–512 mW/cm2, the peak yield of Iz was 34% at a light intensity of 51.2 mW/cm2. By varying the irradiation time, the maximum yield of Iz (34–35%) was obtained with irradiation times of 5–20 min using the 450 nm LED source at an intensity of 13.8 mW/cm2. Using the 365 nm LED source at an intensity of 25.6 mW/cm2, the maximum Iz yield obtained was 31% at irradiation times of 2–5 min. Thus, we obtained conditions that can provide an Iz yield of up to 35%.
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(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
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Open AccessReview
One-Pot Reactions of Triethyl Orthoformate with Amines
by
Elina Marinho
Reactions 2023, 4(4), 779-800; https://doi.org/10.3390/reactions4040045 - 2 Dec 2023
Abstract
One-pot reactions offer advantages like easy automation, higher product yields, minimal waste generation, operational simplicity, and thus reduced cost, time and energy. This review presents a comprehensive overview of one-pot reactions including triethyl orthoformate and amines as valuable and efficient reagents for carrying
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One-pot reactions offer advantages like easy automation, higher product yields, minimal waste generation, operational simplicity, and thus reduced cost, time and energy. This review presents a comprehensive overview of one-pot reactions including triethyl orthoformate and amines as valuable and efficient reagents for carrying out two-, three- or four-component organic reactions.
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(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
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Open AccessReview
Chlorophyll Sensitization of TiO2: A Mini-Review
by
Maria E. K. Fuziki, Angelo M. Tusset, Onélia A. A. dos Santos and Giane G. Lenzi
Reactions 2023, 4(4), 766-778; https://doi.org/10.3390/reactions4040044 - 1 Dec 2023
Abstract
Recent studies have shown that chlorophyll sensitization can improve the performance of semiconductors like TiO2 in photocatalytic reactions and light-harvesting technologies, such as solar cells. Faced with the search for renewable energy sources and sustainable technologies, the application of this natural pigment
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Recent studies have shown that chlorophyll sensitization can improve the performance of semiconductors like TiO2 in photocatalytic reactions and light-harvesting technologies, such as solar cells. Faced with the search for renewable energy sources and sustainable technologies, the application of this natural pigment has been gaining prominence. The present work addresses some of the main possibilities of chlorophyll-TiO2 combination, presenting the most relevant aspects affecting chlorophyll extraction and TiO2 sensitization.
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(This article belongs to the Special Issue Traditional and Innovative Catalysts for Reactions of Industrial Interest)
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