THEORETICAL-STUDIES OF THERMAL SYN ELIMINATION-REACTIONS - THE RELATIVE RATES OF ETHYL FORMATE, ETHYL XANTHATE, AND ETHYL PHOSPHINATE ELIMINATIONS

The thermal elimination reactions of ethyl formate, ethyl xanthate, an d ethyl phosphinate were examined in order to address the mechanistic details in this class of E(i) reactions. The reactants, products, and transition structures were fully optimized at the RHF/6-31G level wit h MP2/6-31G single point energies calculated on the HF optimized stru ctures. In addition, the electrostatic potential derived atomic charge s were calculated for each reactant and transition structure. The resu lts of this study show that the C-alpha-O bond is lengthened to a grea ter degree than the CbetaH bond in the transition structure and that t he degree of the lengthening correlates with both calculated and exper imental rate trends. It appears that the C-alpha-O bond dissociates in advance of the CbetaH bond in this asynchronous reaction and that the relative rates of these reactions depend primarily on the ease with w hich the C-alpha-O bond can dissociate.