Pub Date : 2019-05-01DOI: 10.1177/1468678319825898
Xiaojun Tan, Xiuhui Lu
X2Si=Sn: (X = H, Me, F, Cl, Br, Ph, Ar, etc.) are a new chemical species. The cycloaddition reactions of X2Si=Sn: are a new field of stannylene chemistry. The mechanism of the cycloaddition reaction between singlet state Me2Si=Sn: and ethene has been investigated for the first time here using second-order Møller-Plesset perturbation theory together with the 6-311++G** basis set for C, H and Si atoms and the LanL2dz basis set for Sn atoms. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction process presented is that the 5p unoccupied orbital of Sn in Me2Si=Sn: and the π orbital of ethene form a π → p donor–acceptor bond resulting in the formation of an intermediate. The instability of this intermediate makes it isomerize to a four-membered Si-heterocyclic ring stannylene. Because the 5p unoccupied orbital of the Sn atom in the four-membered Si-heterocyclic ring stannylene and the π orbital of ethene form a π → p donor–acceptor bond, the four-membered Si-heterocyclic ring stannylene further combines with ethene to form another intermediate. Because the Sn atom in this intermediate assumes sp3 hybridization after the transition state, the intermediate isomerizes to a Si-heterocyclic spiro-Sn-heterocyclic ring compound. This result indicates the modes of cycloaddition reactions between X2Si=Sn: and symmetric π-bonded compounds, i.e. this study opens up a new field for stannylene chemistry.
{"title":"Ab initio study of mechanism of forming a Si-heterocyclic spiro-Sn-heterocyclic ring compound by cycloaddition reaction of Me2Si=Sn: and ethene","authors":"Xiaojun Tan, Xiuhui Lu","doi":"10.1177/1468678319825898","DOIUrl":"https://doi.org/10.1177/1468678319825898","url":null,"abstract":"X2Si=Sn: (X = H, Me, F, Cl, Br, Ph, Ar, etc.) are a new chemical species. The cycloaddition reactions of X2Si=Sn: are a new field of stannylene chemistry. The mechanism of the cycloaddition reaction between singlet state Me2Si=Sn: and ethene has been investigated for the first time here using second-order Møller-Plesset perturbation theory together with the 6-311++G** basis set for C, H and Si atoms and the LanL2dz basis set for Sn atoms. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction process presented is that the 5p unoccupied orbital of Sn in Me2Si=Sn: and the π orbital of ethene form a π → p donor–acceptor bond resulting in the formation of an intermediate. The instability of this intermediate makes it isomerize to a four-membered Si-heterocyclic ring stannylene. Because the 5p unoccupied orbital of the Sn atom in the four-membered Si-heterocyclic ring stannylene and the π orbital of ethene form a π → p donor–acceptor bond, the four-membered Si-heterocyclic ring stannylene further combines with ethene to form another intermediate. Because the Sn atom in this intermediate assumes sp3 hybridization after the transition state, the intermediate isomerizes to a Si-heterocyclic spiro-Sn-heterocyclic ring compound. This result indicates the modes of cycloaddition reactions between X2Si=Sn: and symmetric π-bonded compounds, i.e. this study opens up a new field for stannylene chemistry.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"7 1","pages":"114 - 121"},"PeriodicalIF":0.7,"publicationDate":"2019-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78878810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-24DOI: 10.1177/1468678319825727
B. Qin, Yang Tian, Pengxiang Zhang, Zuoyin Yang, Guoxin Zhang, Zhao Cai, Yaping Li
Density functional theory calculations were employed to investigate the electrochemical oxygen reduction reaction on the (111) and (100) surfaces of cobalt(II) oxide. Different mechanisms were applied to evaluate the oxygen reduction reaction performance of cobalt(II) oxide structures in terms of the Gibbs free energy and density of states. A variety of intermediate structures based on associative and dissociative mechanisms were constructed and optimized. As a result, we estimated the catalytic activity by calculating the free energy of the intermediates and constructing free energy diagrams, which suggested that the oxygen reduction reaction Gibbs free energy on cobalt(II) oxide (111) and (100) surfaces based on the associative mechanism is smaller than that based on the dissociative mechanism, demonstrating that the associative mechanism should be more likely to be the oxygen reduction reaction pathway. Moreover, the theoretical oxygen reduction reaction activity on the cobalt(II) oxide (111) surface was found to be higher than that on the cobalt(II) oxide (100) surface. These results shed light on the rational design of high-performance cobalt(II) oxide oxygen reduction reaction catalysts.
{"title":"A density functional theory study of the oxygen reduction reaction on the (111) and (100) surfaces of cobalt(II) oxide","authors":"B. Qin, Yang Tian, Pengxiang Zhang, Zuoyin Yang, Guoxin Zhang, Zhao Cai, Yaping Li","doi":"10.1177/1468678319825727","DOIUrl":"https://doi.org/10.1177/1468678319825727","url":null,"abstract":"Density functional theory calculations were employed to investigate the electrochemical oxygen reduction reaction on the (111) and (100) surfaces of cobalt(II) oxide. Different mechanisms were applied to evaluate the oxygen reduction reaction performance of cobalt(II) oxide structures in terms of the Gibbs free energy and density of states. A variety of intermediate structures based on associative and dissociative mechanisms were constructed and optimized. As a result, we estimated the catalytic activity by calculating the free energy of the intermediates and constructing free energy diagrams, which suggested that the oxygen reduction reaction Gibbs free energy on cobalt(II) oxide (111) and (100) surfaces based on the associative mechanism is smaller than that based on the dissociative mechanism, demonstrating that the associative mechanism should be more likely to be the oxygen reduction reaction pathway. Moreover, the theoretical oxygen reduction reaction activity on the cobalt(II) oxide (111) surface was found to be higher than that on the cobalt(II) oxide (100) surface. These results shed light on the rational design of high-performance cobalt(II) oxide oxygen reduction reaction catalysts.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"47 1","pages":"122 - 131"},"PeriodicalIF":0.7,"publicationDate":"2019-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75035827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-24DOI: 10.1177/1468678319825735
Junrui Cao, Yuhui Ma
Non-isothermal pyrolysis and gasification of Enteromorpha prolifera (also known as Ulva prolifera) under a CO2 atmosphere were investigated by thermogravimetry analysis. The gaseous products were measured online with Fourier transform infrared spectroscopy coupled with thermogravimetry. The kinetic parameters of pyrolysis and gasification reactions were obtained using the Coats–Redfern method. The experimental results showed that Enteromorpha prolifera had two derivative thermogravimetry peaks centered at 240 and 800°C, indicating the pyrolysis of organics and gasification of char, respectively. Carboxylic acids, ethers, and alcohols were the dominating condensable products generated from pyrolysis between 230 and 300°C. H2O, CH4, and aliphatic hydrocarbons were also formed in this temperature range, and they were also continuously released at higher temperatures, indicating further polymerization of the freshly generated pyrolytic char. CO was mainly produced between 700 and 900°C, and its yield was much higher than that of the pyrolytic gaseous products. The Ginstling equation (the D4 model) proved to be the most probable mechanism function for both the pyrolysis and gasification stages, with activation energies of 138.30 and 93.43 kJ mol−1, respectively.
{"title":"Pyrolysis and gasification of macroalgae Enteromorpha prolifera under a CO2 atmosphere using the thermogravimetry–Fourier transform infrared spectroscopy technique","authors":"Junrui Cao, Yuhui Ma","doi":"10.1177/1468678319825735","DOIUrl":"https://doi.org/10.1177/1468678319825735","url":null,"abstract":"Non-isothermal pyrolysis and gasification of Enteromorpha prolifera (also known as Ulva prolifera) under a CO2 atmosphere were investigated by thermogravimetry analysis. The gaseous products were measured online with Fourier transform infrared spectroscopy coupled with thermogravimetry. The kinetic parameters of pyrolysis and gasification reactions were obtained using the Coats–Redfern method. The experimental results showed that Enteromorpha prolifera had two derivative thermogravimetry peaks centered at 240 and 800°C, indicating the pyrolysis of organics and gasification of char, respectively. Carboxylic acids, ethers, and alcohols were the dominating condensable products generated from pyrolysis between 230 and 300°C. H2O, CH4, and aliphatic hydrocarbons were also formed in this temperature range, and they were also continuously released at higher temperatures, indicating further polymerization of the freshly generated pyrolytic char. CO was mainly produced between 700 and 900°C, and its yield was much higher than that of the pyrolytic gaseous products. The Ginstling equation (the D4 model) proved to be the most probable mechanism function for both the pyrolysis and gasification stages, with activation energies of 138.30 and 93.43 kJ mol−1, respectively.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"93 1","pages":"132 - 142"},"PeriodicalIF":0.7,"publicationDate":"2019-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83889899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-22DOI: 10.1177/1468678319825724
Enisa Selimović, T. Soldatović
Substitution reactions of square-pyramidal [ZnCl2(terpy)] complex (terpy = 2,2′:6′,2″-terpyridine) with biologically relevant nucleophiles such as imidazole, glutathione, 1,2,4-triazole, and pyrazine were investigated at pH 7.0 as a function of nucleophile concentration. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions comprised two steps of consecutive displacement of chlorido ligands. Different reaction pathways for the first reaction step of nucleophilic substitution were defined. The order of reactivity of the investigated nucleophiles for the first reaction was imidazole > glutathione > pyrazine > 1,2,4-triazole, while for the second reaction step it was pyrazine > 1,2,4-triazole > imidazole > glutathione.
{"title":"Study on the reactions between dichlorido[2,2′:6′,2″-terpyridine] zinc(II) and biologically relevant nucleophiles in aqueous solution","authors":"Enisa Selimović, T. Soldatović","doi":"10.1177/1468678319825724","DOIUrl":"https://doi.org/10.1177/1468678319825724","url":null,"abstract":"Substitution reactions of square-pyramidal [ZnCl2(terpy)] complex (terpy = 2,2′:6′,2″-terpyridine) with biologically relevant nucleophiles such as imidazole, glutathione, 1,2,4-triazole, and pyrazine were investigated at pH 7.0 as a function of nucleophile concentration. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions comprised two steps of consecutive displacement of chlorido ligands. Different reaction pathways for the first reaction step of nucleophilic substitution were defined. The order of reactivity of the investigated nucleophiles for the first reaction was imidazole > glutathione > pyrazine > 1,2,4-triazole, while for the second reaction step it was pyrazine > 1,2,4-triazole > imidazole > glutathione.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"114 1","pages":"105 - 113"},"PeriodicalIF":0.7,"publicationDate":"2019-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77061053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-10DOI: 10.1177/1468678319825689
N. Mozayyeni, A. Morsali, M. Bozorgmehr, S. Beyramabadi
Using Fe6(OH)18(H2O)6 as a ring cluster model for superparamagnetic iron oxide nanoparticles, noncovalent configurations and three mechanisms of covalent functionalization of superparamagnetic iron oxide nanoparticles with cyclophosphamide an anticancer drug were studied. Quantum molecular descriptors, solvation, and binding energies of noncovalent interactions were investigated the in gas and solution phases at the B3LYP and M06-2X density functional levels. In the vicinity of superparamagnetic iron oxide nanoparticles, the reactivity of the drug increases, showing cyclophosphamide can probably bind to superparamagnetic iron oxide nanoparticles through Cl (k1 mechanism), P=O (k2 mechanism), and NH in a six-membered ring (k3 mechanism) groups. The activation parameters of all pathways were calculated, indicating the high barriers related to the k1 and k2 mechanisms are higher the barrier related to the k3 mechanism. The k3 mechanism is also spontaneous and exothermic and is therefore the preferred mechanism for covalent functionalization.
{"title":"Mechanistic and energetic studies of superparamagnetic iron oxide nanoparticles as a cyclophosphamide anticancer drug nanocarrier: A quantum mechanical approach","authors":"N. Mozayyeni, A. Morsali, M. Bozorgmehr, S. Beyramabadi","doi":"10.1177/1468678319825689","DOIUrl":"https://doi.org/10.1177/1468678319825689","url":null,"abstract":"Using Fe6(OH)18(H2O)6 as a ring cluster model for superparamagnetic iron oxide nanoparticles, noncovalent configurations and three mechanisms of covalent functionalization of superparamagnetic iron oxide nanoparticles with cyclophosphamide an anticancer drug were studied. Quantum molecular descriptors, solvation, and binding energies of noncovalent interactions were investigated the in gas and solution phases at the B3LYP and M06-2X density functional levels. In the vicinity of superparamagnetic iron oxide nanoparticles, the reactivity of the drug increases, showing cyclophosphamide can probably bind to superparamagnetic iron oxide nanoparticles through Cl (k1 mechanism), P=O (k2 mechanism), and NH in a six-membered ring (k3 mechanism) groups. The activation parameters of all pathways were calculated, indicating the high barriers related to the k1 and k2 mechanisms are higher the barrier related to the k3 mechanism. The k3 mechanism is also spontaneous and exothermic and is therefore the preferred mechanism for covalent functionalization.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"66 1","pages":"101 - 92"},"PeriodicalIF":0.7,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86890386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-10DOI: 10.1177/1468678319830488
Hua Song, Xueyan Dai, N. Jiang, Zijin Yan, Tianhan Zhu, Feng Li
Neodymium (Nd)- or yttrium (Y)- modified bulk Ni2P catalysts (Nd-Ni2P or Y-Ni2P) have been successfully prepared and their catalytic performance in benzofuran hydrodeoxygenation have been investigated. The as-prepared catalysts were characterised by X-ray diffraction, N2 adsorption–desorption, CO uptake and X-ray photoelectron spectroscopy. The addition of Nd or Y, especially Nd, can increase the surface area of the catalysts and promote the formation of smaller and more highly dispersed Ni2P particles. The Nd-Ni2P catalyst showed the highest benzofuran hydrodeoxygenation activity of 95.3% and the O-free products yield of 74.6%, which gives an increase of 25.3% and 35.4% when compared with that found for Ni2P.
{"title":"The effect of neodymium and yttrium on benzofuran hydrodeoxygenation performance over a bulk Ni2P catalyst","authors":"Hua Song, Xueyan Dai, N. Jiang, Zijin Yan, Tianhan Zhu, Feng Li","doi":"10.1177/1468678319830488","DOIUrl":"https://doi.org/10.1177/1468678319830488","url":null,"abstract":"Neodymium (Nd)- or yttrium (Y)- modified bulk Ni2P catalysts (Nd-Ni2P or Y-Ni2P) have been successfully prepared and their catalytic performance in benzofuran hydrodeoxygenation have been investigated. The as-prepared catalysts were characterised by X-ray diffraction, N2 adsorption–desorption, CO uptake and X-ray photoelectron spectroscopy. The addition of Nd or Y, especially Nd, can increase the surface area of the catalysts and promote the formation of smaller and more highly dispersed Ni2P particles. The Nd-Ni2P catalyst showed the highest benzofuran hydrodeoxygenation activity of 95.3% and the O-free products yield of 74.6%, which gives an increase of 25.3% and 35.4% when compared with that found for Ni2P.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"40 1","pages":"29 - 36"},"PeriodicalIF":0.7,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76350591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-10DOI: 10.1177/1468678319825693
C. Han, Hua Song, N. Jiang, Yanguang Chen, Feng Li, Tianzhen Hao
A series of Ti-incorporated bulk Ni2P catalysts was prepared by means of temperature-programmed reduction, and the role of metallic Ti on the structure and catalytic activity of the Ni2P catalysts was studied. For this purpose, bulk Ni2P catalysts with metal Ti contents of 0.005 wt%, 0.01 wt%, and 0.02 wt% were synthesized. X-ray diffraction, CO uptake, Brunauer–Emmett–Teller measurements, and X-ray photoelectron spectroscopy were utilized to characterize the catalysts. Addition of titanium could increase the surface area and promote the formation of small, highly dispersed Ni2P particles. The Ti0.02-Ni2P system with a Ti molar fraction of 0.02 showed the highest hydrodesulfurization activity of 99.6%, which was an increase of 44% compared with that found for the bulk Ni2P.
{"title":"Effect of Ti on dibenzothiophene hydrodesulfurization performance over bulk Ni2P","authors":"C. Han, Hua Song, N. Jiang, Yanguang Chen, Feng Li, Tianzhen Hao","doi":"10.1177/1468678319825693","DOIUrl":"https://doi.org/10.1177/1468678319825693","url":null,"abstract":"A series of Ti-incorporated bulk Ni2P catalysts was prepared by means of temperature-programmed reduction, and the role of metallic Ti on the structure and catalytic activity of the Ni2P catalysts was studied. For this purpose, bulk Ni2P catalysts with metal Ti contents of 0.005 wt%, 0.01 wt%, and 0.02 wt% were synthesized. X-ray diffraction, CO uptake, Brunauer–Emmett–Teller measurements, and X-ray photoelectron spectroscopy were utilized to characterize the catalysts. Addition of titanium could increase the surface area and promote the formation of small, highly dispersed Ni2P particles. The Ti0.02-Ni2P system with a Ti molar fraction of 0.02 showed the highest hydrodesulfurization activity of 99.6%, which was an increase of 44% compared with that found for the bulk Ni2P.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"29 1","pages":"45 - 54"},"PeriodicalIF":0.7,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83396589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-10DOI: 10.1177/1468678319825686
Guilin Cheng, Lin-yan Wang, Chengjun Jiang
This study employed Nb2O5.nH2O for the dehydration of butane-2,3-diol, which could be derived from biomass or waste gas using a fermentation process. The experiments were conducted at a temperature ranging from 220 °C to 260 °C and a weight hourly space velocity of 0.01–0.05 min−1. There are three main products that include methyl ethyl ketone, isobutyraldehyde, and butadiene. The yield of products increased with the reaction temperature. Rate data for the dehydration reaction were well represented by Langmuir–Hinshelwood kinetics with adsorption parameters in the rate equations, which assumed the formation of products was reversible with single-site reaction. The apparent activation energies for the dehydration reaction of methyl ethyl ketone, isobutyraldehyde, and butadiene obtained from the Arrhenius plot data were 19.5, 24.0, and 23.7 kJ mol−1, respectively. The adsorption energies for butane-2,3-diol, methyl ethyl ketone, isobutyraldehyde, and butadiene were −182.4, −142.1, −136.1, and −105.6 kJ mol−1, respectively.
{"title":"Kinetic modeling of butane-2,3-diol dehydration over Nb2O5.nH2O","authors":"Guilin Cheng, Lin-yan Wang, Chengjun Jiang","doi":"10.1177/1468678319825686","DOIUrl":"https://doi.org/10.1177/1468678319825686","url":null,"abstract":"This study employed Nb2O5.nH2O for the dehydration of butane-2,3-diol, which could be derived from biomass or waste gas using a fermentation process. The experiments were conducted at a temperature ranging from 220 °C to 260 °C and a weight hourly space velocity of 0.01–0.05 min−1. There are three main products that include methyl ethyl ketone, isobutyraldehyde, and butadiene. The yield of products increased with the reaction temperature. Rate data for the dehydration reaction were well represented by Langmuir–Hinshelwood kinetics with adsorption parameters in the rate equations, which assumed the formation of products was reversible with single-site reaction. The apparent activation energies for the dehydration reaction of methyl ethyl ketone, isobutyraldehyde, and butadiene obtained from the Arrhenius plot data were 19.5, 24.0, and 23.7 kJ mol−1, respectively. The adsorption energies for butane-2,3-diol, methyl ethyl ketone, isobutyraldehyde, and butadiene were −182.4, −142.1, −136.1, and −105.6 kJ mol−1, respectively.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"1 1","pages":"18 - 28"},"PeriodicalIF":0.7,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89918583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-26DOI: 10.1177/1468678319832382
A. Tahan, A. Shiroudi
Kinetic rate constants for the oxidation reactions of OH radicals with CH3SH (1), C2H5SH (2), n-C3H7SH (3) and iso-C3H7SH (4) under inert conditions (Ar) over the temperature range 252−430 K have been studied using the CBS-QB3 composite method. Kinetic rate constants under atmospheric pressure and in the fall-off regime have been estimated using transition state theory (TST) and statistical Rice–Ramsperger–Kassel–Marcus (RRKM) theory. Comparison with experiment confirms that in the OH-addition pathways 1−4 leading to the related products, the first bimolecular reaction step has effective negative activation energies around −2.61 to 3.70 kcal mol−1. Effective rate coefficients have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a result of the negative activation energies, pressures larger than 104 bar would be required to restore to some extent the validity of this approximation for all the channels. By comparison with experimental data, all our calculations for both the OH-addition and H-abstraction reaction pathways indicate that from a kinetic viewpoint and in line with the computed reaction energy barriers, the most favourable process is the OH-addition pathway to n-C3H7SH to yield the [n-C3H7SH−OH]• species, whereas under thermodynamic control of the bimolecular reactions (R−SH+OH•), the most abundant product derived from the H-abstraction pathway will be the [n-C3H7 S•+H2O] species.
{"title":"Oxidation reaction mechanism and kinetics between OH radicals and alkyl-substituted aliphatic thiols: OH-addition pathways","authors":"A. Tahan, A. Shiroudi","doi":"10.1177/1468678319832382","DOIUrl":"https://doi.org/10.1177/1468678319832382","url":null,"abstract":"Kinetic rate constants for the oxidation reactions of OH radicals with CH3SH (1), C2H5SH (2), n-C3H7SH (3) and iso-C3H7SH (4) under inert conditions (Ar) over the temperature range 252−430 K have been studied using the CBS-QB3 composite method. Kinetic rate constants under atmospheric pressure and in the fall-off regime have been estimated using transition state theory (TST) and statistical Rice–Ramsperger–Kassel–Marcus (RRKM) theory. Comparison with experiment confirms that in the OH-addition pathways 1−4 leading to the related products, the first bimolecular reaction step has effective negative activation energies around −2.61 to 3.70 kcal mol−1. Effective rate coefficients have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a result of the negative activation energies, pressures larger than 104 bar would be required to restore to some extent the validity of this approximation for all the channels. By comparison with experimental data, all our calculations for both the OH-addition and H-abstraction reaction pathways indicate that from a kinetic viewpoint and in line with the computed reaction energy barriers, the most favourable process is the OH-addition pathway to n-C3H7SH to yield the [n-C3H7SH−OH]• species, whereas under thermodynamic control of the bimolecular reactions (R−SH+OH•), the most abundant product derived from the H-abstraction pathway will be the [n-C3H7 S•+H2O] species.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"50 1","pages":"157 - 174"},"PeriodicalIF":0.7,"publicationDate":"2019-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90272888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-22DOI: 10.1177/1468678319834831
Adel Boualouache, A. Boucenna, Ghazi Otmanine
By employing a combined approach of the unity bond index–quadratic exponential potential method and density functional theory within the generalized gradient approximation, we have studied the interaction of intermediates in the ethanol dehydrogenation process to ethyl acetate on Cu, Ag, Ni, Pd, Pt, Co, Au and Ir(111) transition metal surfaces. Binding energies and geometries were optimized for the main intermediates of this process. Electronic structures were computed for some intermediates/transition metal systems. We also calculated the activation energies for the elementary steps of the reactions. The results show that amid the studied surfaces, Cu(111) stabilizes ethoxy and acetyl species, preventing their dissociation. Inducing the η2 binding mode of acetaldehyde by alloying Cu with Ni, Co, Pd, Pt or Ir can enhance the catalytic proprieties of the Cu(111) clean surface.
{"title":"Interaction of intermediates with transition metal surfaces in the dehydrogenation of ethanol to ethyl acetate: A theoretical investigation","authors":"Adel Boualouache, A. Boucenna, Ghazi Otmanine","doi":"10.1177/1468678319834831","DOIUrl":"https://doi.org/10.1177/1468678319834831","url":null,"abstract":"By employing a combined approach of the unity bond index–quadratic exponential potential method and density functional theory within the generalized gradient approximation, we have studied the interaction of intermediates in the ethanol dehydrogenation process to ethyl acetate on Cu, Ag, Ni, Pd, Pt, Co, Au and Ir(111) transition metal surfaces. Binding energies and geometries were optimized for the main intermediates of this process. Electronic structures were computed for some intermediates/transition metal systems. We also calculated the activation energies for the elementary steps of the reactions. The results show that amid the studied surfaces, Cu(111) stabilizes ethoxy and acetyl species, preventing their dissociation. Inducing the η2 binding mode of acetaldehyde by alloying Cu with Ni, Co, Pd, Pt or Ir can enhance the catalytic proprieties of the Cu(111) clean surface.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"47 1","pages":"74 - 91"},"PeriodicalIF":0.7,"publicationDate":"2019-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80498703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：