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Theoretical Study of O-CH₃ Bond Dissociation Enthalpy in Anisole Systems.

ABSTRACT: Understanding ubiquitous methyl transfer reactions requires a systematic study of thermodynamical parameters that could reveal valuable information about the nature of the chemical bond and the feasibility of those processes. In the present study, the O-CH₃ bond dissociation enthalpies (BDEs) of 67 compounds belonging to phenol/anisole systems were calculated employing the Gaussian-4 (G4) method. Those compounds contain different substituents including alkyl groups, electron-donating groups (EDGs), and electron-withdrawing groups (EWGs). The results show that the bigger branched alkyl groups and EDGs will destabilize the O-CH₃ bond, while EWGs have the opposite effect. A combination of different effects including steric effects, hydrogen bonds, and substituents and their position can achieve around 20 kcal/mol difference compared to the basic phenyl frame. Also, the linear correlation between σ_p ⁺ and O-CH₃ BDE can provide a reference for the O-CH₃ BDE prediction. The present study represents a step forward to establish a comprehensive O-CH₃ BDE database to understand the substituent effect and make its contribution to the rational design of inhibitors and drugs.

SUBMITTER: Li R

PROVIDER: S-EPMC8412933 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Theoretical Study of O-CH<sub>3</sub> Bond Dissociation Enthalpy in Anisole Systems.

Li Rui R Du Tianshu T Liu Jingxing J Aquino Adelia J A AJA Zhang Jianyu J

ACS omega 20210819 34

Understanding ubiquitous methyl transfer reactions requires a systematic study of thermodynamical parameters that could reveal valuable information about the nature of the chemical bond and the feasibility of those processes. In the present study, the O-CH<sub>3</sub> bond dissociation enthalpies (BDEs) of 67 compounds belonging to phenol/anisole systems were calculated employing the Gaussian-4 (G4) method. Those compounds contain different substituents including alkyl groups, electron-donating ...[more]

PMID: 34497890

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Project description:Thermodynamic properties, i.e., bond dissociation energies and enthalpy of formation, of chlorinated and brominated polycyclic aromatic hydrocarbons play a fundamental role in understanding their formation mechanisms and reactivity. Computational electronic structure calculations routinely used to predict thermodynamic properties of various species are limited for these compounds due to large computational cost to obtain accurate results by employing high-level wave function theory methods. In this work, a number of composite model chemistry methods (CBS-QB3, G3MP2, G3, and G4) are used to compute bond dissociation energies and enthalpies of formation of small to medium-size chlorinated and brominated polycyclic aromatic hydrocarbon compounds. The enthalpy of formation is derived via the atomization method and compared against the recommended values. Statistical analysis indicates that G4 is the best method. For comparison, three commonly used density functional theory (DFT) methods (M06-2X, ωB97X-D and B2PLYP-D3) with various basis sets including 6-311++G(d, p), cc-pVTZ, and cc-pVQZ in the prediction of bond dissociation energies and enthalpies of formation have been tested using the optimized geometries at the same M06-2X/6-311++G(d, p) level of theory. It is found that ωB97X-D/6-311++G(d, p) shows the best performance in computing the bond dissociation energies, while ωB97X-D/cc-pVTZ exhibits the best prediction in enthalpy of formation of the studied reaction systems. The structural effect on the bond dissociation energies and enthalpy of formation of chlorinated and brominated polycyclic aromatic hydrocarbons are then systematically analyzed. Based on comparisons of the various methods, reliable DFT methods are recommended for future theoretical studies on large chlorinated and brominated polycyclic aromatic hydrocarbons considering both accuracy and computational cost. This work, to the authors' knowledge, is the first to systematically benchmark theoretical methods for the accurate prediction of thermodynamic properties for chlorinated and brominated polycyclic aromatic hydrocarbons.

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Theoretical Study of O-CH₃ Bond Dissociation Enthalpy in Anisole Systems.

Publications

Theoretical Study of O-CH<sub>3</sub> Bond Dissociation Enthalpy in Anisole Systems.

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Theoretical Study of O-CH3 Bond Dissociation Enthalpy in Anisole Systems.

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Theoretical Study of O-CH<sub>3</sub> Bond Dissociation Enthalpy in Anisole Systems.

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OmicsDI is part of the ELIXIR infrastructure

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Theoretical Study of O-CH₃ Bond Dissociation Enthalpy in Anisole Systems.