Reaction mechanism of 1,2-hydrogen migration of hydrogen peroxide

1990 ◽  
Vol 68 (5) ◽  
pp. 666-673 ◽  
Author(s):  
Enric Bosch ◽  
José M. Lluch ◽  
Juan Bertrán
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Mechanism ◽  
Water Molecule ◽  
Energy Barrier ◽  
Electron Distribution ◽  
Reaction Path ◽  
Bifunctional Catalyst ◽  
Reaction Coordinate ◽  
Intrinsic Reaction Coordinate ◽  
Hydrogen Migration

The 1,2-hydrogen migration of hydrogen peroxide has been investigated by abinitio methods and the Intrinsic Reaction Coordinate (IRC) has been constructed. An analysis of the evolution of the electron distribution along the reaction path has shown that the shifting hydrogen behaves as a proton. This transferring proton polarizes the O—O bond of the hydrogen peroxide that becomes broken at the transition state. If a water molecule is allowed to participate in the reaction, the energy barrier is noticeably lowered, this water molecule acting as a bifunctional catalyst. Keywords: 1,2-hydrogen migration, hydrogen peroxide, proton transfer, bifunctional catalyst, Intrinsic Reaction Coordinate.

scholarly journals New Insight into the Chloroacetanilide Herbicide Degradation Mechanism through a Nucleophilic Attack of Hydrogen Sulfide

2018 ◽  
Vol 19 (10) ◽  
pp. 2864 ◽  
Author(s):  
José Mora ◽  
Cristian Cervantes ◽  
Edgar Marquez
Keyword(s):  
Hydrogen Sulfide ◽  
Reaction Mechanism ◽  
Activation Barrier ◽  
Degradation Mechanism ◽  
Reaction Force ◽  
Transition States ◽  
Reaction Coordinate ◽  
Basis Sets ◽  
Nucleophilic Attack ◽  
Intrinsic Reaction Coordinate

The nucleophilic attack of hydrogen sulfide (HS−) on six different chloroacetanilide herbicides was evaluated theoretically using the dispersion-corrected hybrid functional wB97XD and the 6-311++G(2d,2p) Pople basis sets. The six evaluated substrates were propachlor (A), alachlor (B), metolachlor (C), tioacetanilide (D), β-anilide (E), and methylene (F). Three possible mechanisms were considered: (a) bimolecular nucleophilic substitution (SN2) reaction mechanism, (b) oxygen assistance, and (c) nitrogen assistance. Mechanisms based on O- and N-assistance were discarded due to a very high activation barrier in comparison with the corresponding SN2 mechanism, with the exception of compound F. The N-assistance mechanism for compound F had a free activation energy of 23.52 kcal/mol, which was close to the value for the corresponding SN2 mechanism (23.94 kcal/mol), as these two mechanisms could occur in parallel reactions with almost 50% of each one. In compounds A to D, an important electron-withdrawing effect of the C=O and C=S groups was seen, and consequently, the activation free energies in these SN2 reactions were smaller, with a value of approximately 18 kcal/mol. Instead, compounds E and F, which have a CH2 group in the β-position, presented a higher activation free energy (≈22 kcal/mol). Good agreement was found between experimental and theoretical values for all cases, and a reaction force analysis was performed on the intrinsic reaction coordinate profile in order to gain more details about the reaction mechanism. Finally, from the natural bond orbital (NBO) analysis, it was possible to evaluate the electronic reorganization through the reaction pathway where all the transition states were early in nature in the reaction coordinate (δBav < 50%); the transition states corresponding to compounds A to D turned out to be more synchronous than those for compounds E and F.

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

scholarly journals On the 3D → 2D Isomerization of Hexaborane(12)

Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 28-38
Author(s):  
Josep M. Oliva-Enrich ◽  
Ibon Alkorta ◽  
José Elguero ◽  
Maxime Ferrer ◽  
José I. Burgos
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Transition States ◽  
Three Dimensional ◽  
Reaction Coordinate ◽  
Intrinsic Reaction Coordinate ◽  
Limiting Factor ◽  
Two Dimensional ◽  
Axis Of Rotation

By following the intrinsic reaction coordinate connecting transition states with energy minima on the potential energy surface, we have determined the reaction steps connecting three-dimensional hexaborane(12) with unknown planar two-dimensional hexaborane(12). In an effort to predict the potential synthesis of finite planar borane molecules, we found that the reaction limiting factor stems from the breaking of the central boron-boron bond perpendicular to the C2 axis of rotation in three-dimensional hexaborane(12).

scholarly journals Molecular simulation on mechanism of thiophene hydrodesulfurization on surface of Ni2P

2021 ◽  
pp. 014459872199495
Author(s):  
Songjian Du ◽  
Tingting Li ◽  
Xinwei Wang ◽  
Liqiang Zhang ◽  
Zhengda Yang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Heavy Oil ◽  
Density Functional ◽  
Reaction Path ◽  
Functional Theory ◽  
Thiophene Hydrodesulfurization ◽  
Cracking Reaction ◽  
Materials Studio ◽  
Optimal Reaction

Hydrodesulfurization reaction, as the last step of hydrothermal cracking reaction, is of great significance for the reduction of viscosity and desulfurization of heavy oil. Based on Density Functional Theory and using Dmol3 module of Materials Studio, this research simulated the adsorption and hydrodesulfurization of thiophene on Ni2P (001) surface, and discussed the hydrodesulfurization reaction mechanism of thiophene on Ni2P (001) surface. It was found that the direct hydrodesulfurization of thiophene had more advantages than the indirect hydrodesulfurization of thiophene. Finally, the optimal reaction path was determined: C4H4S+H2→C4H6.

Kinetics Studies for Catalytic Oxidation of Methyl Orange over the Heterogeneous Fe/Beta Catalysts

2013 ◽  
Vol 807-809 ◽  
pp. 361-364
Author(s):  
Fang Guo ◽  
Jun Qiang Xu ◽  
Jun Li
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Reaction Mechanism ◽  
Methyl Orange ◽  
Incipient Wetness Impregnation ◽  
Kinetics Studies ◽  
Optimum Reaction ◽  
Catalyst Dosage ◽  
Oxidation Degradation ◽  
Degradation Of Methyl Orange

The Fe/Beta catalysts were prepared by conventional incipient wetness impregnation. The catalysis oxidation degradation of methyl orange was carried out in catalyst and H2O2 process. The results indicated that the catalyst and hydrogen peroxide were more benefit to degradation of methyl orange. The reaction condition was optimized. The optimum reaction process was as follow: iron amount of catalyst was 1.25%, the catalyst dosage and H2O2 concentration was 1 mg/L and 1.5 mg/L, and reaction temperature was 70 °C. The apparent activation energy (65 KJ/mol) was obtained according to the arrhenius formula, which was benefit to study the reaction mechanism.

scholarly journals Reaction Mechanism of Aqueous Benzene with Hydrogen Peroxide by Transient Absorbance Spectra

2004 ◽  
Vol 20 (09) ◽  
pp. 1112-1117 ◽  
Author(s):  
Zhu Cheng-Zhu ◽  
◽  
Zhang Ren-Xi ◽  
Zheng Guang-Ming ◽  
Ouyang Bin ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Mechanism ◽  
Transient Absorbance ◽  
Absorbance Spectra

Laboratory Stopped-Flow XAFS Apparatus. Structure Determination of the Short-Lived Peroxochromium Intermediate Formed during Reduction Process of Chromate(VI) Ion by Hydrogen Peroxide

1997 ◽  
Vol 52 (6) ◽  
pp. 711-718 ◽  
Author(s):  
Y. Inada ◽  
S. Funahashi
Keyword(s):  
Hydrogen Peroxide ◽  
Fine Structure ◽  
Water Molecule ◽  
Reduction Process ◽  
Stopped Flow ◽  
Structure Parameters ◽  
X Ray ◽  
Reaction Intermediate ◽  
X Ray Absorption

In order to determine the structure parameters of the reaction intermediate formed during the reduction process of chromate(VI) ion by hydrogen peroxide, a laboratory stopped-flow X-ray absorption fine structure (XAFS ) apparatus, which was constructed by a rotating anode X-ray generator, an energy scanning spectrometer, a stopped-flow assembly, and X-ray detectors, was newly developed. Using the apparatus, the Cr K -edge XAFS spectrum of the reaction intermediate was measured. One oxo group, two peroxo groups, and one water molecule are coordinated to the Cr(VI) center in the intermediate, CrO(O2)2(H2O ) , with Cr - O bond lengths of 157, 168, and 193 pm, respectively. The geometry around the Cr(VI) center is probably 6-coordinate pentagonal pyramidal.

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