Monochloroacetic Acid: Chlorine Bubbled into Hot Acetic Acid with a Little Acetic Anhydride (Hammond, Celanese, US 2,503,334)

Chlorine on its own hardly touches acetic acid. A little acetic anhydride turns into acetyl chloride, which carries the chlorine onto the acid; topping up the anhydride every few hours keeps the reaction going, and after 12 hours the liquor sets to crystals on cooling. Result: about 150 parts of monochloroacetic acid crystals, 97.5 % pure, from 95-100 parts acetic acid (82 % conversion). Source: Hammond, John and Page, US 2,503,334 (Celanese, 1950). Picture drawn by Youblob.