Non‐statistical dynamics for the allene oxide to cyclopropanone conversion

Abstract

Whether one is interested in mode selective chemistry or non‐statistical reaction dynamics, understanding which vibrational modes contribute to a reaction is important. We investigated the ring‐opening of 2‐methylideneoxirane (a.k.a., allene oxide) to the oxyallyl diradical and subsequent ring‐closure to cyclopropanone using hybrid density functional theory (DFT) and atom centered density matrix propagation (ADMP) molecular dynamics in Gaussian. DFT calculations for this ring‐opening and subsequent ring‐closure show that the energetics allow for the possibility of non‐statistical events, as suggested by the similarities between the imaginary vibrational modes and a twisting motion. ADMP simulations starting near the ring‐opening transition state lead to faster ring‐closure than for simulations starting from the intermediate diradical with the same energy. Analysis of the simulation data identified the presence of a vibrational state near 200 cm−1, corresponding to a disrotatory twisting motion. Selectively exciting this mode leads to a fast reaction time of 50 fs. This work predicts non‐statistical dynamics in the conversion of allene oxide to cyclopropanone.