Abstract: A series of mesylates of general type ArC (CH3)(S02Ph) OMs, 14, have been prepared and studied under solvolytic conditions. The Hammett p value in methanol is-7.98. A solvent effect study on 14b, where Ar= p-CH3C6H4, gave a good correlation with YoTS values and an m value of 0.85. These data were interpreted in terms of the involvement of a- sulfonyl-substituted carbocations, which have a large demand for aryl group stabilization. ...