3-Methylcatechol → 2-Hydroxy-6-methylbenzenesulfonic acid

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Reaction Steps

A 500 ml three-neck flask, equipped with magnetic stirrer, addition funnel and reflux condenser, was charged with 108.0g (1.0 mole) of m-cresol. Sulfuric acid (96.5%), 147.9g was added dropwise during 25 minutes, while the temperature rose to 80°. External heating by mantle raised the temperature to 107° during 15 min. and Sample 1 was withdrawn. The sample was diluted with water, made basic with aqueous sodium hydroxide and the water was evaporated. The resultant salts, 11.0 g. were fused with 25 g. potassium hydroxide for 40 min. at 235°-330° under a nitrogen atmosphere. The mass was diluted with water, acidified with hydrochloric acid to pH 2 and extracted with four portions of 100 ml each of ether. The solvent was boiled off leaving only 0.5 g. of residue. Infrared and nuclear magnetic resonance showed it to contain 36% m-cresol, 26% diethyl ether solvent and 38% aryl carboxylic acids. There was no evidence of orcinol, methylhydroquinone and methylcatechol. Continuous liquid-liquid extraction of the aqueous phase with ether for five hours only produced 0.2 g. of additional product. A repeat fusion on ca. 25 ml of reaction mixture produced 45 g. of salts which were fused with 100 g. of potassium hydroxide for 35 min. at 350° to 360°. Work-up produced only 2.2 g. in which only m-cresol could be identified. The sulfonation resulted in the formation of substantially only m-cresolsulfonic acid isomers wherein the acid group is in ortho and/or para position relative to the hydroxyl group. The failure to obtain methylhydroquinone and/or 4-methylcatechol by fusion from the above m-cresol-sulfonic acids is not surprising in view of Barth and Senhofer's [Ber. 9, 969 (1876)] failure to fuse o- and p- phenolsulfonic acids.

Provenance & Evidence