The electronic structure of peracids. Functional models for cytochrome p-450

An extensive set of ground state ab initio and semiempirical molecular orbital calculations has been performed on both peroxytrifluoroacetic and peroxyacetic acids. The equilibrium geometry of peroxyacetic acid was calculated with the STO-3G and MINDO/3 methods, and peroxide rotational barriers for both peracids were obtained with STO-3G and PCILO. Extended basis set calculations with the 6-31G^** basis were performed for both peracids to compare the electronic structures of these two compounds. Electrostatic potential maps in the region of the peroxide bonds of both peracids were also calculated using INDO wavefunetions. These results are discussed with respect to the enhanced reactivity of peroxytrifluoracetic acid relative to peroxyacetic acid and the nature of the oxygen electrophilicity in these compounds and by analogy in cytochrome P-450, for which peroxytrifluoroacetic acid is considered to be an effective chemical model.