A direct dynamics trajectory study of F-+CH3OOHreactive 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(CO)2 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 CH2(OH)(2)center dot center dot center dot 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(CO)2 path whose energy release is -27 kcal/mol. Other product channels not observed, and which have a lower energy than that for the E(CO)2 path, are F- + CO + H-2 + H2O (-43 kcal/mol), F- + CH2O + H2O (-51 kcal/mol), and F- + CH2(OH)(2) (-60 kcal/mol). Formation of the CH3OOH center dot center dot center dot F- complex, with randomization of its internal energy, is important, and this complex dissociates via the E(CO)2 mechanism. Trajectories which form HF + CH3OO- are nonstatistical events and, for the 4 ps direct dynamics simulation, are not mediated by the CH3OOH center dot center dot center dot F- complex. Dissociation of this complex to form HF + CH3OO- may occur on longer time scales.