Temperature dependences of the rate constants and branching ratios for the reactions of F-(H2O)0-5 with CH3Br

Article abstract of DOI:10.1021/jp970492a

The effects of solvation, isotopic substitution, and temperature on the reactions of F^-(H₂O)_n=0-5 with CH₃Br have been studied. The reaction of n = 0 produces Br^- as the exclusive ionic product and has a rate which is fast, approaching the collision rate, with a slight negative temperature dependence of T^-0.9±0.1. The reaction of n = 1 is a factor of 3 slower with a slightly larger negative temperature dependence, T^-1.1±0.05. The main ionic product is Br^-, with smaller amounts of Br^-(H₂O) also formed. Substituting D₂O for H₂O causes the n = 1 rate constant to increase slightly. The n = 2 reaction has a much slower rate and produces three ionic products: Br^-, Br^-(H₂O), and F^-(H₂O)₂(CH₃Br). The n = 3 reaction is immeasurably slow. The rate constants for the n = 4 and 5 reactions are greater than those for the n = 3 reaction. The ionic products of these reactions are F^-(H₂O)₃ and F^-(H₂O)₄, respectively.