scholarly journals Influence of the number of water molecules on the mechanism of N-sulfinylaniline hydrolysis

2005 ◽  
Vol 83 (9) ◽  
pp. 1588-1596 ◽  
Author(s):  
Elena V Ivanova ◽  
Heidi M Muchall
Keyword(s):  
Water Molecule ◽  
Density Functional ◽  
Weak Interactions ◽  
Activation Barrier ◽  
Water Molecules ◽  
Functional Theory ◽  
High Enthalpy ◽  
Rate Determining Step ◽  
Enthalpy Of Activation ◽  
Hydrolysis Of

The mechanism of the uncatalyzed hydrolysis of N-sulfinylaniline (Ph-N=S=O) has been studied with B3LYP/6-31+G(2d,2p) in the gas phase, with explicit treatment of water molecules. Hydrolysis involves water attack on sulfur, with a close to perpendicular alignment of a water molecule and the NSO plane in both prereaction complexes and transition states for the rate-determining step. Consequently, the distance of the weak S···O interaction, together with the efficiency of protonation of either nitrogen (attack across the N=S bond) or oxygen (attack across the S=O bond) atoms of the NSO group, determines the height of the activation barrier for hydrolysis. While the reaction with one water molecule is characterized by an unreasonably high enthalpy of activation, a cooperative effect from the weak interactions appears with the inclusion of a second water molecule, where both participate in the reaction, and the activation enthalpy drops significantly. The preference for attack across the S=O bond that is found in the reaction with one water molecule switches to a dominance of attack across the N=S bond in the reaction with three water molecules.Key words: N-sulfinylaniline, hydrolysis, mechanism, density functional theory (DFT).

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 Computational Evidence Suggests That 1-chloroethanol May Be an Intermediate in the Thermal Decomposition of 2-chloroethanol into Acetaldehyde and HCl

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Oscar Ventura ◽  
Vincenzo Barone
Keyword(s):  
Aqueous Solution ◽  
Water Molecule ◽  
Gas Phase ◽  
Density Functional ◽  
Water Molecules ◽  
Functional Theory ◽  
Direct Transformation ◽  
The Density Functional Theory ◽  
Successive Step ◽  
The One

<p>The dehalogenation of 2-chloroethanol (2ClEtOH) in gas phase with and without participation of catalytic water molecules has been investigated using methods rooted into the density functional theory. The well-known HCl elimination leading to vinyl alcohol (VA) was compared to the alternative elimination route towards oxirane and shown to be kinetically and thermodynamically more favorable. However, the isomerization of VA to acetaldehyde in the gas phase, in the absence of water, was shown to be kinetically and thermodynamically less favorable than the recombination of VA and HCl to form the isomeric 1-chloroethanol (1ClEtOH) species. This species is more stable than 2ClEtOH by about 6 kcal mol<sup>-1</sup>, and the reaction barrier is 22 kcal mol<sup>-1</sup> vs 55 kcal mol<sup>-1</sup> for the direct transformation of VA to acetaldehyde. In a successive step, 1ClEtOH can decompose directly to acetaldehyde and HCl with a lower barrier (29 kcal mol<sup>-1</sup>) than that of VA to the same products (55 kcal mol<sup>-1</sup>). The calculations were repeated using a single ancillary water molecule (W) in the complexes 2ClEtOH_W and 1ClEtOH_W. The latter adduct is now more stable than 2ClEtOH_W by about 8 kcal mol<sup>-1</sup>, implying that the water molecule increased the already higher stability of 1ClEtOH in the gas phase. However, this catalytic water molecule lowers dramatically the barrier for the interconversion of VA to acetaldehyde (from 55 to 6 kcal mol<sup>-1</sup>). This barrier is now smaller than the one for the conversion to 1ClEtOH (which also decreases, but not so much, from 22 to 12 kcal mol<sup>-1</sup>). Thus, it is concluded that while 1ClEtOH may be a plausible intermediate in the gas phase dehalogenation of 2ClEtOH, it is unlikely that it plays a major role in water complexes (or, by inference, aqueous solution). It is also shown that neither in the gas phase nor in the cluster with one water molecule, the oxirane path is competitive with the VA alcohol path.</p>

scholarly journals Density functional theory meta GGA study of water adsorption in MIL-53(Cr)

2019 ◽  
Vol 34 (3) ◽  
pp. 227-232 ◽  
Author(s):  
E. Cockayne
Keyword(s):  
Density Functional Theory ◽  
Water Molecule ◽  
Density Functional ◽  
Critical Concentration ◽  
Metal Organic Framework ◽  
Water Dimer ◽  
Hydroxyl Group ◽  
Water Molecules ◽  
Generalized Gradient ◽  
Functional Theory

We use density functional theory meta-generalized gradient approximation TPSS + D3(BJ) + U + J calculations to investigate the energetics and geometry of water molecules in the flexible metal-organic framework material Materials of Institut Lavoisier (MIL)-53(Cr) as a function of cell volume. The critical concentration of water to cause the transition from the large pore (lp) to the narrow pore (np) structure is estimated to be about 0.13 water molecule per Cr. At a concentration x = 1 water molecule per Cr, the zero-temperature np and lp configurations each have a hydrogen bond between the H of each framework hydroxyl group and water oxygen (OW). At intermediate volumes, water dimer-like configurations are observed. A concentration x = 1.25 leads to hydrogen bonding between water molecules in the np phase that is absent for x = 1. Our results suggest possible mechanisms for pore closing in hydrated MIL-53(Cr).

scholarly journals New insights on the theoretical study of hydrolysis mechanism of carbon disulfide (CS2) at low temperature: A density functional theory study

2022 ◽  
Author(s):  
Yue Wang ◽  
Guijian Zhang ◽  
Xin Shi ◽  
Ming Deng ◽  
Lihong Tang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Exothermic Reaction ◽  
Transition States ◽  
Nbo Analysis ◽  
Functional Theory ◽  
Hydrolysis Mechanism ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract Density functional theory (DFT) is used to investigate the two-step hydrolysis mechanism of CS2. By optimizing the structure of reactants, intermediates, transition states, and products, the conclusion shows that the first step of CS2 (CS2 reacts with H2O first to form COS intermediate); The second step (COS intermediate reacts with H2O to form H2S and CO2). Therefore, hydrogen migration is crucial to the mechanism of CS2 hydrolysis. In the first step of the reaction, the rate-determining step in both the single C=S path and the double C=S path has a higher barrier of 199.9 kJ/mol, but the 127.9 kJ/mol barrier in the double C=S path has a lower barrier of 142.8 kJ/mol in the single C=S path. So the double C=S path is better. Similarly, the order of the barriers for the three paths in the second reaction is C=S path < C=S path and C=O path < C=O path. So the C=S path is better. Also, to further explore the reaction of CS2 hydrolysis, the natural bond orbital (NBO) analysis of the transition states was carried out. Besides, to further explain which reaction path is better, the hydrolysis kinetics of CS2 was analyzed. It was found that the hydrolysis of CS2 was an exothermic reaction, and the increase in temperature was unfavorable to the reaction. During the hydrolysis of CS2, the six reaction paths are parallel and competitive. The results will provide a new way to study the catalytic hydrolysis of CS2.

scholarly journals Computational Evidence Suggests That 1-chloroethanol May Be an Intermediate in the Thermal Decomposition of 2-chloroethanol into Acetaldehyde and HCl

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Oscar Ventura ◽  
Vincenzo Barone
Keyword(s):  
Aqueous Solution ◽  
Water Molecule ◽  
Gas Phase ◽  
Density Functional ◽  
Water Molecules ◽  
Functional Theory ◽  
Direct Transformation ◽  
The Density Functional Theory ◽  
Successive Step ◽  
The One

<p>The dehalogenation of 2-chloroethanol (2ClEtOH) in gas phase with and without participation of catalytic water molecules has been investigated using methods rooted into the density functional theory. The well-known HCl elimination leading to vinyl alcohol (VA) was compared to the alternative elimination route towards oxirane and shown to be kinetically and thermodynamically more favorable. However, the isomerization of VA to acetaldehyde in the gas phase, in the absence of water, was shown to be kinetically and thermodynamically less favorable than the recombination of VA and HCl to form the isomeric 1-chloroethanol (1ClEtOH) species. This species is more stable than 2ClEtOH by about 6 kcal mol<sup>-1</sup>, and the reaction barrier is 22 kcal mol<sup>-1</sup> vs 55 kcal mol<sup>-1</sup> for the direct transformation of VA to acetaldehyde. In a successive step, 1ClEtOH can decompose directly to acetaldehyde and HCl with a lower barrier (29 kcal mol<sup>-1</sup>) than that of VA to the same products (55 kcal mol<sup>-1</sup>). The calculations were repeated using a single ancillary water molecule (W) in the complexes 2ClEtOH_W and 1ClEtOH_W. The latter adduct is now more stable than 2ClEtOH_W by about 8 kcal mol<sup>-1</sup>, implying that the water molecule increased the already higher stability of 1ClEtOH in the gas phase. However, this catalytic water molecule lowers dramatically the barrier for the interconversion of VA to acetaldehyde (from 55 to 6 kcal mol<sup>-1</sup>). This barrier is now smaller than the one for the conversion to 1ClEtOH (which also decreases, but not so much, from 22 to 12 kcal mol<sup>-1</sup>). Thus, it is concluded that while 1ClEtOH may be a plausible intermediate in the gas phase dehalogenation of 2ClEtOH, it is unlikely that it plays a major role in water complexes (or, by inference, aqueous solution). It is also shown that neither in the gas phase nor in the cluster with one water molecule, the oxirane path is competitive with the VA alcohol path.</p>

scholarly journals Quantum mechanical investigations of base-catalyzed cycloaddition reaction between phenylacetylene and azidobenzene

2020 ◽  
pp. 174751982094625
Author(s):  
Mohammad Abd Al-Hakim Badawi ◽  
Sultan T Abu-Orabi
Keyword(s):  
Density Functional ◽  
Activation Barrier ◽  
Cycloaddition Reaction ◽  
Product Formation ◽  
Dipolar Cycloaddition ◽  
Kinetic Properties ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Charged System ◽  
The Difference

In this study, the mechanism for both the Huisgen 1,3-dipolar cycloaddition and the base-catalyzed cycloaddition reactions between phenylacetylene and azidobenzene has been investigated with density functional theory, namely at the M06-2X/6-31G(d) computational level. Later, the reaction has been modeled with a representative simple alkyne and a simple azide to concentrate solely on how the difference bases affect the mechanism of the reaction between phenylacetylene and azidobenzene as charged components. In this study, another mechanism of this reaction with uncharged components has been proposed to compare the calculated thermodynamic and kinetic properties for charged and uncharged systems. The calculated activation barrier differences between the catalyzed and the uncatalyzed reactions are consistent with the faster and the regioselective synthesis of the triazole product in the presence of solvents. The calculated barrier of the rate-determining step in the base-catalyzed mechanism with the uncharged system is lower than that with charged systems. Finally, the reaction leading to final product formation in uncharged system is more spontaneous than that in the charged system, and the same applies to the total reaction in the presence of solvents.

scholarly journals Bias-dependent local structure of water molecules at a metallic interface

2018 ◽  
Vol 9 (1) ◽  
pp. 62-69 ◽  
Author(s):  
Luana S. Pedroza ◽  
Pedro Brandimarte ◽  
Alexandre Reily Rocha ◽  
M.-V. Fernández-Serra
Keyword(s):  
Density Functional Theory ◽  
Water Molecule ◽  
Electronic Properties ◽  
Local Structure ◽  
Density Functional ◽  
Water Molecules ◽  
Functional Theory ◽  
Structure Of Water ◽  
Metallic Interfaces ◽  
Non Equilibrium Green’S Function

We combine Density Functional Theory (DFT) and Non-Equilibrium Green’s Function (NEGF) methods to study the electronic properties and atomic forces of a water molecule at metallic interfaces.

A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

2018 ◽  
Author(s):  
Kyle Reeves ◽  
Damien Dambournet ◽  
Christel Laberty-Robert ◽  
Rodolphe Vuilleumier ◽  
Mathieu Salanne
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Water Dissociation ◽  
Water Molecules ◽  
Chemical Doping ◽  
Charge Balance ◽  
Functional Theory ◽  
Adsorption Of Water ◽  
Properties Of Materials ◽  
Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO<sub>2</sub> with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a<br>monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the<br>variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in<br>the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

2018 ◽  
Author(s):  
Kyle Reeves ◽  
Damien Dambournet ◽  
Christel Laberty-Robert ◽  
Rodolphe Vuilleumier ◽  
Mathieu Salanne
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Water Dissociation ◽  
Water Molecules ◽  
Chemical Doping ◽  
Charge Balance ◽  
Functional Theory ◽  
Adsorption Of Water ◽  
Properties Of Materials ◽  
Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO<sub>2</sub> with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a<br>monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the<br>variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in<br>the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

scholarly journals Weak Interactions in Cocrystals of Isoniazid with Glycolic and Mandelic Acids

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 328
Author(s):  
Raquel Álvarez-Vidaurre ◽  
Alfonso Castiñeiras ◽  
Antonio Frontera ◽  
Isabel García-Santos ◽  
Diego M. Gil ◽  
...  
Keyword(s):  
Density Functional ◽  
Glycolic Acid ◽  
Weak Interactions ◽  
Three Dimensional ◽  
Functional Theory ◽  
Molecular Systems ◽  
X Ray Crystallography ◽  
Hydroxycarboxylic Acids ◽  
Non Covalent Interactions ◽  
Covalent Interactions

This work deals with the preparation of pyridine-3-carbohydrazide (isoniazid, inh) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or d,l-mandelic acid (H2ma) resulted in the formation of cocrystals or salts of composition (inh)·(H2ga) (1) and [Hinh]+[Hma]–·(H2ma) (2) when reacted with isoniazid. An N′-(propan-2-ylidene)isonicotinic hydrazide hemihydrate, (pinh)·1/2(H2O) (3), was also prepared by condensation of isoniazid with acetone in the presence of glycolic acid. These prepared compounds were well characterized by elemental analysis, and spectroscopic methods, and their three-dimensional molecular structure was determined by single crystal X-ray crystallography. Hydrogen bonds involving the carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and its derivatives. The remaining hydrogen-bonding sites on the isoniazid backbone vary based on the steric influences of the derivative group. These are contrasted in each of the molecular systems. Finally, Hirshfeld surface analysis and Density-functional theory (DFT) calculations (including NCIplot and QTAIM analyses) have been performed to further characterize and rationalize the non-covalent interactions.

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