The solvolysis of 4-methoxybenzyl chloride (1) and bromide (3), and 1-(4-methoxyphenyl)ethyl chloride (4) in a variety of solvents were carried out. The observation of linear correlation using the dualparameter Grunwald-Winstein equation, and the positive azide salt effect indicate significant nucleophilic solvent participation for 1 and 3. A smaller deviation of log k (in 100% 2,2,2-trifluoroethanol) for the bromide 3 than chloride 1 in the log k ؊ Y BnX plots reveals a lesser extent of nucleophilic participation and is also in harmony with the greater nucleofugality of the bromide ion. The use of a low k Br /k Cl ratio as evidence for the presence of solvent participation is discussed. The observed -deuterium kinetic isotope effect of 1.08 to 1.21 measured for 1 and 3 is inconsistent with the magnitude generally considered for a concerted mechanism.

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The solvolysis of 2-bromo-2-methylpropane (1B), 2-bromo-2-methylbutane (2B), 2-bromo-2,3-dimethylbutane (3B), 2-bromo-2,3,3-trimethylbutane (4B), 3-bromo-3-methylpentane (5B), 3-bromo-2,3-dimethylpentane (6B), 3-bromo-2,2,3-trimethylpentane (7B), 3-bromo-3-ethylpentane (8B), 3-bromo-3-ethyl-2-methylpentane (9B) and 2-bromo-2,4,4-trimethylpentane (11B) in 15 to 21 solvents was studied, and correlation analyses by using the single-and dual-parameter Grunwald-Winstein equations (Eqns 1 and 2) were examined. Substrates 7B, 9B and 11B showed excellent linear relationship (R ³ 0.997) in the logk -Y Br plots and indicated limiting S N 1 mechanism for the solvolysis. On the other hand, bromides 1B-6B and 8B gave linear correlations (R = 0.987-0.996) with the dual-parameter (Y Br and N OTs ) equation (2) only, which indicated the presence of significant nucleophilic solvent participation. Normal trends of reactivity due to the relief of B-strain could be found in the poorly nucleophilic trifluoroethanol. Similar to the corresponding chlorides, the overwhelming influence of nucleophilic solvent assistance results in the observed inverse order of reactivity: k(2B) > k(3B), k(5B) > k(6B) and k(8B) > k(9B).