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Saber

versão On-line ISSN 2343-6468

Resumo

Transesterification reaction of several acid carboxylic esters, employing basic and acid catalysis. Saber [online]. 2015, vol.27, n.3, pp.470-480. ISSN 2343-6468.

Transesterification reaction of several acid carboxylic esters with methanol, via SN2-like, using HCl and NH3 as catalysts, have been studied using electronic structure methods of interchange-correlations B3PW91, combined with 6-31++G(d,p) basis set. Activation and thermodynamics parameters show that in the presence of ammonia and hydrogen chloride, the values of free energy of activation are much smaller (ΔΔG< 0) than without catalyst, favoring the transesterification process, being, in most cases, hydrogen chloride the mostactive catalyst. The analysis of natural bond orbital (NBO, for its acronym in English) shows that the catalytic process is concerted and synchronous, where the leaving group protonation and nucleophile deprotonation coordinates evolve simultaneously.

Palavras-chave : DFT; transition state; NBO; catalytic activity.

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