Sulfonation and sulfation in reactions of C‐methylated phenols and anisoles with sulfur trioxide. 4‐Substituted phenyl hydrogen sulfates: Effective reagents for transsulfonation

Abstract The sulfation and sulfonation of the methyl‐ and dimethylphenols with 0.9 and 4.0 equiv. of SO 3 in nitromethane at 0°C have been studied. On using 0.9 equiv. of SO 3 , the sulfonic acid product distributions are determined by the ortho ‐ and para ‐directing effect of the activating hydroxy substituent. In the reactions with 4.0 equiv. of SO 3 , the sulfonic acid product distributions are affected by the predominant initial formation and the subsequent sulfonation of the corresponding phenyl hydrogen sulfates, of which the bulky OSO 3 H substituent is electronically deactivating and (mainly) para ‐directing. For comparison, the sulfonation of the methylanisoles, phenyl methanesulfonate and 2,3‐dihydrobenzofuran was also studied. The sulfonation of 1,3‐dimethoxybenzene in ( 2 H 8 )dioxane at 17.0°C has been studied using 4‐substituted phenyl hydrogen sulfates as transsulfonating agents. The transsulfonation was found to be first order with respect to the phenyl hydrogen sulfates and independent of the 1,3‐dimethoxybenzene concentration. The reaction constant of the transsulfonation reaction was determined to be ρ = 2.0 ± 0.2.