Unexpected Mechanistic Behavior in Peracid Epoxidation of Alkenes

The peracid epoxidation reaction is frequently employed in the synthesis of complex organic compounds, including alcohols, pharmaceuticals, and thermoset polymers. The original mechanistic study, published in 1950, proposed a concerted “butterfly” mechanism that is now commonly accepted [1]. Our quantum molecular dynamics simulations using density functional theory (DFT) methods, however, show many trajectories in which a proton is transferred to the ‘wrong’ oxygen of the peracid, inconsistent with the accepted mechanism. Additionally, we see a few reaction trajectories leading to unexpected rearrangement products analogous to those observed experimentally from highly strained alkenes [2]. [1] P.D. Bartlett, Rec. Chem. Prog. 11 (1950) 47. [2] Kenneth W. Hill, Ph. D. Dissertation, UCSB (1986).