Retentive solvolysis. 13 The number and the stability of carbocation intermediate in the SN1 phenolysis. Salt effect on retentive phenolyses of optically active 2,2-dimethyl-1-(p-substituted phenyl)propyl p-nitrobenzoates.

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The salt effect of (n-Bu)4NClO4 and NaOPh on the polarimetric and titrimetric rate constants (kp and kt, respectively) has been examined for the SN1 solvolyses of optically active 2,2-dimethyl-1-(p-methoxyphenyl)propyl (1) and 2,2-dimethyl-1-phenylpropyl p-nitrobenzoates (2) in pure phenol solvent. Four patterns, A, B, C, and D of the kp–kt profile against the added salt concentration have been observed for the phenolyses of 1, 2, and 2,2-dimethyl-1-(p-nitrophenyl)propyl p-nitrobenzoate (3). The patterns can specify the number of the sequential ion-pair intermediates (i.e., one or two), the product-forming stage (i.e., the 1st or the 2nd intermediate), and the species of reactant at the product-forming step (i.e., solvent phenol molecule, the phenoxide, or the perchlorate). The feature of the pattern of the kp–kt profile is predominantly controlled by two factors, (i) the stability of the carbocation intermediate derived from the substrates 1–3 and (ii) the nucleophilicity of the added salt. The patterns of salt effect on the product distribution (% of ROPh, o- and p-RC6H4OH) are also compatible with such rationalization of the four patterns.
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