A Study of the OH~- -Induced β-Elimination Reactions of 2-(4-Chloroethyl)pyridine, 2-(2-Chloroethyl)pyridine, 1-Methyl-2-(4-chloroethyl)pyridinium Iodide and 1-Methyl-2-(2-chloroethyl)pyridinium Iodide in Acetonitrile/Water

摘要

Second-order rate constants have been determined for the title reactions in OH~-/H_2O and in OH~-/ (CH_3CN/H_2O) [30/70, 60/40, and 85/15 (v/v) mixtures]. A relatively small increase in reactivity is observed for the four substrates upon increasing the percentage of CH_3CN in the solvent mixture. The methyl activating factors (k_(OH~-)~(NCH_3)/k_(OH~-)~N) are also slightly affected by the solvent composition. On the other hand, the high acceleration of the reaction by meth-ylation of the pyridine ring amounts to 10~4— 10~6 according to an E1cb mechanism.