Rate constants of solvolysis of a-tert-butyl(2-naphthyl)methyl chloride (1), 9-fluorenyl chloride (2) and a series of monosubstituted benzhydryl chlorides (3) in a wide range of solvents were measured. Grunwald-Winsteintype correlation analysis of log k for 2 and 3 against Y BnCl , with or without nucleophilicity N, yielded less satisfactory linear correlations than that against log k(1). A new scale of solvent ionizing power, Y xBnCl , for the correlation of solvolytic reactivities of benzylic chlorides with extended charge delocalization based on log k(1) was developed. Application to the mechanistic study suggested the solvolysis of 2 and 4-nitrobenzhydryl chloride were non-limiting. Hammett plots against ' constants exhibited more negative r values in less nucleophilic solvents. In a benzhydryl chloride containing a strong deactivating substituent, such as 4-nitro, the positive charge delocalizes mainly over the unsubstituted ring in the cationic transition state. The uneven charge distribution was also confirmed by Mulliken population analysis at the level of the RHF/6-31G * //RHF/3-21G

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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).