Hydrochloric Acid → 2,4-Dichloro-5-carboxybenzenesulfinic acid

Participants

Reaction Conditions

Reaction Steps

A three liter flask equipped with a mechanical stirrer, thermometer and dropping funnel is charged with sodium sulfite (378 g,; 3.0 moles) and water (1 liter). The solution is cooled in an ice bath and treated with 2,4-dichloro-5-chlorosulfonylbenzoic acid (290 g.; 1.0 mole) and 10N sodium hydroxide (290 ml.) simultaneously in small portions over a period of 1.5 hours keeping the temperature below 20° C. and the pH of the reaction at 9. When the addition of the reagents is complete, the reaction is stirred for 3 hours at 25° C. then cooled to 10° C. and acidified with concentrated hydrochloric acid (440 ml.). The 2,4-dichloro-5-carboxybenzenesulfinic acid which precipitates is filtered, washed with ice water, then used in the next step without further purification.

Provenance & Evidence