Theoretical organic chemistry / by Julius B. Cohen.

  • Cohen, Julius B. (Julius Berend), 1859-1935.
Date:
1942
Catalogue details

Licence: In copyright

Credit: Theoretical organic chemistry / by Julius B. Cohen. Source: Wellcome Collection.

    197/636 (page 175)
    THE ACID CHLORIDES, THE ANHYDRIDES, AND THE AMIDES The Acid or Acyl Chlorides are prepared by the action of phos¬ phorus trichloride or pentachloride on the fatty acids. Acetic acid and phosphorus trichloride give acetyl chloride, phosphorus oxide, and hydrochloric acid; when the pentachloride is used, phosphorus oxychloride and hydrochloric acid are formed— 3CH3-COOH + 2PCI3 = 3CH3-COCl + 3HCI + P2Os. Acetyl chloride. ch3-co-oh + PC15 = CHyCO-Cl + HC1 + POCl3. A more convenient reagent is thionyl chloride, the by-products of which escape as gases. CH3-COOH + SOCl2 = CH3-CO*Cl + S02 + HC1. Formyl chloride, H*COCl, is unknown. It probably decom¬ poses at once into carbon monoxide and hydrochloric acid. Expt. 58. Preparation of Acetyl Chloride.—A distilling flask, through the neck of which a tap-funnel is inserted, is attached to a condenser and receiver. The receiver should be connected with a tower of soda-lime, to absorb the hydrochloric acid evolved; otherwise, the operation must be conducted in a fume-cupboard. Fifty grams of glacial acetic acid are placed in the flask, and 40 grams of phosphorus trichloride are slowly added from the tap-funnel. The flask is gently warmed in the water-bath to 40°-50°, until the evolution of hydrochloric acid gas slackens. The water-bath is then heated to boiling, when the acetyl chloride distils. It boils at 550. These compounds are denoted as chlorides of the acid radicals, or as acid or acyl chlorides. Their structure represents them as substitution products of the aldehydes, and they yield aldehydes on reduction (p. 177). Their general formula is