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采用密度泛函理论(DFT)的B3LYP方法,在6-311++G(d,p)基组水平上,研究了在无催化剂、H_2O参与、H_3O~+参与3种条件下苯并噻吩-2-甲酸脱羧的微观反应机理。结果表明,在无催化剂或H_2O参与条件下,苯并噻吩-2-甲酸的脱羧反应的活化能分别为249.1和246.5 kJ.mol~(-1)。在H_3O~+参与的反应中,反应主要经历了噻吩环α-C的质子化、羧基的水合以及C-C键断开的过程,羧基的水合反应为决速步骤,其活化能为177.6 kJ·mol~(-1),而C-C键断开所需克服的能垒仅为32.8 kJ·mol~(-1),从而表明H_3O~+能促进反应的进行。
The B3LYP method of density functional theory (DFT) was applied to study the effect of benzothiophene-benzaldehyde on the basis of 6-311 ++ G (d, p) group without any catalyst, H 2 O and H 3 O + Micro-reaction mechanism of decarboxylation of 2-formic acid. The results show that the activation energy of decarboxylation of benzothiophene-2-carboxylic acid is 249.1 and 246.5 kJ · mol -1, respectively, in the absence of catalyst or H 2 O. The reaction of H_3O ~ + involved the protonation of the α-C thiophene ring, the hydration of the carboxyl group and the cleavage of the CC bond. The hydration reaction of the carboxyl group was the rate-determining step with an activation energy of 177.6 kJ · mol ~ (-1). However, the energy barrier to be overcome by CC bond breaking is only 32.8 kJ · mol -1, indicating that H_3O ~ + can promote the reaction.