Ab Initio MP2 and DFT Study of the Thermal Syn Elimination Reaction in Ethyl Formate

The thermal elimination reaction that appears in some polycarbonates has been studied by density functional
theory (DFT) and ab initio methods of different levels. This work has been focused in the elimination process
of ethyl formate, as a good model of this kind of reaction. Different minima and the transition state have
been found to characterize the thermal elimination reaction, and the activation energy has been obtained. In
this study, we have used different methods to calculate the contribution of the correlation energy; different
basis sets were also employed. This will allow us to perform an analysis of the influence of the applied
method in the obtained results to study the thermal elimination. The lengthening of the bonds has also been
analyzed to shown how concerted the thermal elimination is in the ethyl formate. Three minima have been
found for the ethyl formate, two of them are very close and the third is higher in energy. In general, the DFT
method with a B3LYP functional gives a less concerted reaction. A nonplanar transition state is predicted by
most of the methods used.