Application of the aromatic ring parameter (I ) to solvolyses of β-arylalkyl toluene-p-sulfonates

Abstract

The specific rates of solvolysis of a variety of β-arylalkyl toluene-p-sulfonates, where the solvolyses proceed with anchimeric assistance (a k_Δ pathway), are shown to be very well correlated by a Grunwald–Winstein treatment involving Y_OTs and I (the aromatic ring parameter), previously successfully applied to k_c solvolyses of substrates with aryl groups at the α-carbon. A recently proposed alternative treatment, using Y_OTs in conjunction with Y_Δ [a scale derived from 2-methyl-2-(p-methyoxyphenyl)propyl toluene-p-sulfonate solvolyses], is shown to be equivalent to use of Y_OTs plus I; the sensitivity coefficients from the two treatments can be readily interconverted. Three methods (similarity models of type Y_BnX, use of Y_X plus I and use of Y_X plus Y_ΔX have now been proposed for treatment of dispersion in Grunwald–Winstein plots due to the presence in the substrate of conjugated π electrons. The relative efficiencies of these three methods are discussed.