caa a22 4500 605487170 CHVBK 20210128100449.0 cr unu---uuuuu 210128e20150101xx s 000 0 eng 10.1007/s00214-014-1591-5 doi (NATIONALLICENCE)springer-10.1007/s00214-014-1591-5 Acid-catalyzed transesterification and esterification in methanol: a theoretical cluster-continuum investigation of the mechanisms and free energy barriers [Elektronische Daten] [Poliana Silva, Carlos Silva, Luciana Guimarães, Josefredo Pliego Jr.] The mechanism of the acid-catalyzed transesterification reaction was widely studied by experimental methods. However, theoretical studies with reliable calculation of the free energy barrier for solution phase reaction are scarce. In this report, we have done a theoretical investigation (using MP4, X3LYP, CPCM and SMD methods) of the acid-catalyzed transesterification of ethyl acetate and esterification of acetic acid in methanol solution, two prototypical reactions important for biodiesel production via acid catalysis. We have found three mechanisms of the AAC2 type and one mechanism of the AAL2 type. Only one AAC2 mechanism is kinetically viable and involves initial formation of a complex with protonated methanol hydrogen bonded to the ester (acid) carbonyl oxygen. This reaction pathway takes place through several intermediates and transition states, and the highest free energy barriers were estimated as being 23.1 and 22.4kcalmol−1 for transesterification and esterification reactions, respectively. This last value is in good agreement with the experimentally determined free energy barrier of 19.0kcalmol−1. The present results point out the acid-catalyzed transesterification and esterification reactions take place through the classical AAC2 mechanism in methanol solution. Springer-Verlag Berlin Heidelberg, 2014 Biodiesel nationallicence Density functional theory nationallicence Ab initio nationallicence Ester hydrolysis nationallicence Acid catalysis nationallicence Methanolysis nationallicence Silva Poliana Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut Silva Carlos Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut Guimarães Luciana Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut Pliego Jr. Josefredo Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut Theoretical Chemistry Accounts Springer Berlin Heidelberg 134/1(2015-01-01), 1-13 1432-881X 134:1<1 2015 134 214 https://doi.org/10.1007/s00214-014-1591-5 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00214-014-1591-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Silva Poliana Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut NATIONALLICENCE 700 1- Silva Carlos Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut NATIONALLICENCE 700 1- Guimarães Luciana Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut NATIONALLICENCE 700 1- Pliego Jr Josefredo Departamento de Ciências Naturais, Universidade Federal de São João del Rei, 36301-160, São João del-Rei, MG, Brazil aut NATIONALLICENCE 773 0- Theoretical Chemistry Accounts Springer Berlin Heidelberg 134/1(2015-01-01), 1-13 1432-881X 134:1<1 2015 134 214