Ab initio study on thermal decomposition of γ-butyrolactone

All the possible decomposition pathways of γ-butyrolactone were explored with UMP4/6-31G**//UHF/6-31G** methods. Two concerted pathways, one leading to decarbonylation and the other to decarboxylation, and one consecutive pathway, which began with the cleavage between C5-O1 followed by cleavage between C2-C3 leading to decarboxylation, were the three lowest pathways on the potential energy surface. Of the three, the concerted decarbonylation pathway was the easiest energetically. For the decarboxylation process, the consecutive pathway was slightly preferred over the concerted, but both were possible since their energy barriers were higher than that of concerted decarbonylation by about 13 kJ/mol only.