Non-statistical dynamics for the allene oxide to cyclopropanone conversion

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.