Sulfonation of m-Cresol and m-Methylanisole, and NMR Analyses of the Products

Abstract

In the monosulfonation of m-cresol [1] and m-methylanisole [6] with 90% sulfuric acid the effects of reaction temperature and mercury catalysis on the isomer distribution of the 4 and 6-sulfonated products (6-S/4-S) have been studied. The isomer ratios were determined by bicomponent NMR analyses of their signals of methyl protons. All sulfonic acids were finally purified through their anilinium salts by the method described previously. They were chara cterized by the IR, UV and NMR spectra, and were identified into their sulfonamides and s (p-nitrobenzyl) thiouronium salts. The ratios of [1] 6-S/[1] 4-S in the products of the sulfonation of [1] with 90% sulfuric acid for 1/2 hr at 20, 60, 100 and 120°C were 64/36, 52/48, 42/58 and 32/68 respectively. When mercury (II) chloride was used as a catalyst, the ratios of the 6-isomer increased (at 20, 60 and 100°C, they were 81/19, 66/34 and 51/49 respectively). In the sulfonation of [6] at 20-120°C, the ratios of [6] 6-S/[6] 4-S gradually increased from 17/83 to 26/74, and slight effect of mercury (II) chloride was observed.