The solvolysis of 1-alkyl-1-chloro-1-(4-methyl)phenylmethanes (4a-d) in aqueous acetone, aqueous ethanol, aqueous methanol and ethanol-trifluoroethanol was studied. Grunwald-Winstein-type correlation analysis using the Y BnCl scale suggests significant nucleophilic solvent intervention in the case of 1-chloro-1-(4-methyl)phenylethane (4a). Increasing bulkiness of the 1-alkyl substituent from methyl (4a) to ethyl (4b), to isopropyl (4c) and to tert-butyl (4d) resulted in a gradual change to limiting S N 1 mechanisms. The observed excellent linear correlations with Y BnCl and the good solubility in high-water-containing binary solvents made 4d a suitable reference standard for deriving more Y BnCl values. A positive azide salt effect was realized in the solvolysis of 4a but not 4d. A small decrease in the โค-deuterium kinetic isotope effect from 4a to 1-chloro-1-(4-methoxyphenyl)propane (5) suggested the presence of additional stabilization of the benzylic cationic transition state. Howver, no relationship between k(CH 3 )/k(CD 3 ) and the solvent effect was found. The superiority of employing the Y BnCl scale over the combination of Y Cl and I scales in the mehanistic study was observed.