Decarboxylation of pyrrole-2-carboxylic acid: A DFT investigation

► The proton-catalyzed decarboxylation system of pyrrole-2-carboxylic acid aided with H2O were investigated with Gaussian 03 program package at B3LYP/6-311++G∗∗ level, and the decarboxylation mechanism was elucidated in details. ► Then the CPCM model was considered to estimate the solvation effect. ► With the aid with water and H+, pyrrole-2-carboxylic acid is decarboxylated to pyrrole and the protonated carbon dioxide, and the energy barrier of the C-C rupture decreases significantly to 9.77 kcal/mol, which is the most important highlight of this work. The total energy barrier decreases to 33.99 kcal/mol. ► In theoretical and experimental investigations on decarboxylation, the effects of water were seldom considered. ► Moreover, no previous theoretical study of this mechanism is reported.