Study of the OH- + CH2F2 Reaction by Selected Ion Flow Tube Experiments and ab Initio Calculations

Abstract

The reaction OH- + CH2F2 → products has been investigated by both selected ion flow tube (SIFT) experiments and ab initio molecular calculations. The SIFT experiments showed that a bimolecular process, leading to two major anionic products, CHF2- (86%) and F- (11%), and one minor anionic product, HF2- (3%), is in competition with a three-body association leading to OH-·CH2F2 (where values in parentheses are the relative values of the detected anionic products at 300 K). From a pressure dependence study, an upper limit of the bimolecular reaction rate coefficient at 300 K is determined to be (2.4 ± 1.4) × 10-12 cm3 molecule-1 s-1. This shows a small negative temperature dependence, suggesting that the reaction proceeds via an ion-complex intermediate. These experimental results were rationalized using ab initio molecular orbital calculations. Stationary points on the reaction paths of the two main reaction channels were located at both the HF/6-31++G** and MP2/6-31++G** levels. The relative energies of the...