Publication Date:
2015-06-26
Description:
Direct dynamics simulations, with B97-1/ECP/d theory, were performed to study the role of microsolvation for the OH − (H 2 O) + CH 3 I reaction. The S N 2 reaction dominates at all reactant collision energies, but at higher collision energies proton transfer to form CH 2 I − , and to a lesser extent CH 2 I − (H 2 O), becomes important. The S N 2 reaction occurs by direct rebound and stripping mechanisms, and 28 different indirect atomistic mechanisms, with the latter dominating. Important components of the indirect mechanisms are the roundabout and formation of S N 2 and proton transfer pre-reaction complexes and intermediates, including [CH 3 --I--OH] − . In contrast, for the unsolvated OH − + CH 3 I S N 2 reaction, there are only seven indirect atomistic mechanisms and the direct mechanisms dominate. Overall, the simulation results for the OH − (H 2 O) + CH 3 IߙS N 2 reaction are in good agreement with experiment with respect to reaction rate constant, product branching ratio, etc. Differences between simulation and experiment are present for the S N 2 velocity scattering angle at high collision energies and the proton transfer probability at low collision energies. Equilibrium solvation by the H 2 O molecule is unimportant. The S N 2 reaction is dominated by events in which H 2 O leaves the reactive system as CH 3 OH is formed or before CH 3 OH formation. Formation of solvated products is unimportant and participation of the (H 2 O)CH 3 OH---I − post-reaction complex for the S N 2 reaction is negligible.
Print ISSN:
0021-9606
Electronic ISSN:
1089-7690
Topics:
Chemistry and Pharmacology
,
Physics
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