反应详情

The product of Step A is placed in a three-liter flask to which is added water (300 ml.), methanol (500 ml.) sufficient 10N sodium hydroxide to attain a pH of 9 and methyl iodide (520 g.; 3.66 moles). The reaction mixture is refluxed for 36 hours with the occasional addition of 10N sodium hydroxide to maintain pH 9. The alcohol is distilled at reduced pressure and the reaction solution is acidified with hydrochloric acid. The product is filtered, washed with water, dried and recrystallized from ethanol (800 ml.) to give 150 g. (yield 56%) 2,4-dichloro-5-methylsulfonylbenzoic acid, m.p. 210°-211° C.

1. temperatureto maintain pH 9
2. distillationThe alcohol is distilled at reduced pressure
3. filtrationThe product is filtered
4. washwashed with water
5. customdried
6. customrecrystallized from ethanol (800 ml.)
7. customto give 150 g