In this work, the mechanism and intrinsic reaction energy barriers of transmethylation, as the initial stage of the catalytic and non-catalytic anisole decomposition, were investigated by Density Functional Theory (DFT). Molecule analyses indicated that methyl free radical transfer happened in the absence of catalyst, and the catalytic transmethylation over Brønsted acid sites was considered based on the dual electrophilic attack mechanism with protonation and carbocation substitution respectively. Reactions modelling for the formation of methyl-contained compounds in both non-catalytic and catalytic anisole decomposition indicated that the energy barriers were significantly decreased in the presence of catalyst by 60 kcal/mol at the most in the case of o-cresol. The results also revealed that the intrinsic transmethylation orientation preferred the ortho- and para-positions on the acceptor compounds contained oxygen-rich substituents due to its large electronegativity, and the lowest energy barrier was observed in the case of transmethylation towards the para-position of the cresol molecule (54.1 kcal/mol).

中文翻译：

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布朗斯台德酸位上苯甲醚分解过程中反甲基化的机理：密度泛函理论（DFT）研究

在这项工作中，通过密度泛函理论（DFT）研究了甲基转移反应的机理和内在的反应能垒，作为催化和非催化的苯甲醚分解的初始阶段。分子分析表明，在没有催化剂的情况下发生了甲基自由基的转移，并且基于分别具有质子化和碳阳离子取代的双重亲电进攻机理，考虑了布朗斯台德酸位上的催化反甲基化。在非催化和催化苯甲醚分解过程中形成甲基的化合物的反应模型表明，在邻甲酚的情况下，存在催化剂时，能垒最大降低了60 kcal / mol。