A direct dynamics trajectory study of F^- + CH₃OOH reactive collisions reveals a major non-IRC reaction path

A direct dynamics simulation at the B3LYP/6-311+G(d,p) level of theory was used to study the F^- + CH₃OOH reaction dynamics. The simulations are in excellent agreement with a previous experimental study (J. Am. Chem. Soc. 2002, 124, 3196). Two product channels, HF + CH₂O + OH^- and HF + CH₃OO^-, are observed. The former dominates and occurs via an E_CO2 mechanism in which F^- attacks the CH₃-group, abstracting a proton. Concertedly, a carbon-oxygen double bond is formed and OH^- is eliminated. Somewhat surprisingly this is not the reaction path, predicted by the intrinsic reaction coordinate (IRC), which leads to a deep potential energy minimum for the CH ₂(OH)₂⋯F^- complex followed by dissociation to HF + CH₂(OH)O^-. None of the direct dynamics trajectories followed this path, which has an energy release of -63 kcal/mol and is considerably more exothermic than the E_CO2 path whose energy release is -27 kcal/mol. Other product channels not observed, and which have a lower energy than that for the E_CO2 path, are F^- + CO + H₂ + H₂O (-43 kcal/mol), F^- + CH ₂O + H₂O (-51 kcal/mol), and F^- + CH ₂(OH)₂ (-60 kcal/mol). Formation of the CH ₃OOH⋯F^- complex, with randomization of its internal energy, is important, and this complex dissociates via the E_CO2 mechanism. Trajectories which form HF + CH₃OO^- are nonstatistical events and, for the 4 ps direct dynamics simulation, are not mediated by the CH₃OOH⋯F^- complex. Dissociation of this complex to form HF + CH₃OO^- may occur on longer time scales.