4-sulfocatechol

ChEBI: A benzene ring substituted with a sulphonic acid group at position C-1, and hydroxy groups at C-3 and C-4.

0.3 mol of disodium 4-hydroxy-1,3- benzenedisulfonate is reacted with 1.2 mol of sodium hydroxide for 36 min at 340℃; the reaction mass is diluted with water, acidified with sulfuric acid, and boiled to remove sulfur dioxide; the product is extracted with ether. Yield 80%. Pyrocatechol is obtained by hydrolyzing the sulfonic acid group at 190 ℃.