Effect of higher order solvation and temperature on SN2 and E2 reactivity

The reactivity of microsolvated fluoride ions, F-(CH3OH)(0-2), with methyl, ethyl, n-propyl, and t-butyl bromide is evaluated over a broad range of temperatures. Significant decreases inreactivity are observed as either solvation or temperature increases. Increasing solvation increases sensitivity to the reaction barrier as revealed by a larger temperature dependence. These reactions are dominated by an S(N)2 mechanism for the methyl bromide reaction, while the S(N)2 and E2 mechanisms compete for the reactions with ethyl and n-propyl bromide reactions. The elimination mechanism, with some association, dominates the t-butyl bromide reactions. In all cases the unsolvated bromide ion is the primary ionic product. Branching ratios are discussed in both qualitative and quantitative terms for all reactions at 300K. Published by Elsevier B.V.