An attempt to evaluate the effect of proton-coupled electron transfer on the H-abstraction step of the reaction between 1,1-dimethylhydrazine and cytochrome P450 compound I

Abstract

A series of density functional theory and G4 calculations are performed to quantify the extent to which proton-coupled electron transfer (PCET) lowers the barrier for H-abstraction in the reaction between 1,1-dimethylhydrazine (UDMH) and the compound I intermediate of a cytochrome P450 enzyme. The homolytic bond dissociation energy of UDMH is larger than that of 1,4-cyclohexadiene; nevertheless, the H-abstraction barrier is significantly lower for the former substrate. The barrier lowering in the UDMH reaction caused by PCET is roughly estimated to be 9kcal/mol. Valence bond structures are analyzed in detail to figure out how PCET lowers the barrier height.