Transition Structures for [2, 3]-Wittig Rearrangement Basis Set Dependency of Activation Enthalpies

Abstract

Three transition structures (TS- I, TS-. II and TS-III) for [2, 3]-Wittig rearrangement of (allyloxy)methyllithium (1) were optimized at HF/6-31 (+ ) G (* ) levels. The activation enthalpies (δH≠) were evaluated at MP2/6-31 (+)G (* ) levels. There are little differences between the optimized structural parameters but are considerably large energy differences between δH≠ evaluated at MP2 levels. Calculation shows that TS-III has the largest δH≠ among the three transition structures. TS-I and TS-II have the lower δH≠ than TS-III, though the stability and the energy differences (δδH≠) considerably change whether the polarization function (* ) or the diffusion function (+) were included or not in geometry optimization and energy calculation.