Experimental and simulation studies of the OH-(H2O) + CH3I reaction give temperature dependent rate constants which are in excellent agreement. Though there are statistical uncertainties, there is an apparent small decrease in the rate constant as the temperature is increased from - 60 to 125 °C, and for this temperature range the rate constant is ∼ 1.6 times smaller than that for the unsolvated reactants OH- + CH3I. Previous work [J. Phys. Chem. A 117 (2013) 14019] for the unsolvated reaction found that the SN2 and proton transfer pathways, forming CH3OH + I- and CH2I- + H2O, have nearly equal probabilities. However, for the microsolvated OH-(H2O) + CH3I reaction the SN2 pathways dominate. An important contributor to this effect is the stronger binding of H2O to the OH- reactant than to the proton transfer product CH2I-, increasing the barrier for the proton transfer pathway. The effect of microsolvation on the rate constant for the OH-(H2O)0,1 + CH3I reactions agrees with previous experimental studies for X-(H2O)0,1 + CH3Y reactions. The simulations show that there are important non-statistical attributes to the entrance- and exit-channel dynamics for the OH-(H2O) + CH3I reaction.
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© 2015 Walter de Gruyter Berlin/Boston.
- Direct Dynamics
- Proton Transfer
- Zero Point Energy