Benzoic anhydride

Description

Benzoic anhydride is prepared by heating benzoic acid with acetic anhydride in the presence of H3PO4, as described by H. T. Clarke and E. J. Rahrs in 1923 in volume 3 of?Organic Syntheses. It is used primarily as a benzoylating agent in industrial chemical synthesis. Recently, D. Seidel and co-workers?used benzoic anhydride and other inexpensive reagents in acylation reactions?to give products that can be enantiomerically resolved.

Chemical properties

white to almost white crystals or crystalline

The Uses of Benzoic anhydride

Benzoic Anhydride is the more active analogue of benzoic acid formed via dehydration. Benzoic Anhydride is used in the synthesis of a wide range of organic compounds including some dyes. Benzoic Anhyd ride is also used as an arylation agent in the Heck reaction.

The Uses of Benzoic anhydride

In organic syntheses, as benzoylating agent in the manufacture of pharmaceuticals, dyes, and intermediates.

The Uses of Benzoic anhydride

Benzoic anhydride is used as a benzoylating agent in the manufacture of pharmaceuticals, dyes and intermediates. It serves as an arylation agent in the Heck reaction. It is also used to get benzoic acid through dehydration. Further, it is used to prepare furan-2-yl-phenyl-methanone, which is similar to Friedel-Crafts acylation reaction. In addition to this, it is used for the synthesis of carboxylic esters and lactones.

Preparation

To a flask containing 14.0 gm (0.1 mole) of benzoyl chloride and equipped with a stirrer is added 40 ml of dry dioxane and it is cooled to 5°C.Then 10 ml (0.1 mole) of dry pyridine is rapidly added at 5-10°C followed by 1.0 ml (0.056 mole) of water. After stirring for 10-15 min at 0-5°C, the reaction mixture is then poured into a mixture of 75 ml of cone, hydrochloric acid, 75 gm of cracked ice, and 350 ml of water. The product is filtered, washed first for 1 min with a cold 5% solution of sodium bicarbonate and then with water. The product is dried to afford 11.0 gm (97%), m.p. 43°C (recrystallized from a mixture of ether-petroleum ether).

Definition

ChEBI: Benzoic anhydride is an acyclic carboxylic anhydride. It is functionally related to a benzoic acid.

Synthesis Reference(s)

Chemical and Pharmaceutical Bulletin, 35, p. 1262, 1987 DOI: 10.1248/cpb.35.1262
Tetrahedron Letters, 26, p. 1503, 1985 DOI: 10.1016/S0040-4039(00)98536-8

General Description

Benzoic anhydride undergoes Friedel-Crafts acylation reaction with benzene over various ion-exchanged heteropoly acids to yield benzophenone.

Purification Methods

Free it from benzoic acid by washing with NaHCO3, then water, and drying. Crystallise it from *benzene (0.5mL/g) by adding just enough pet ether (b 40-60o) to cause cloudiness, then cool in ice. It can be distilled at 210-220o/20mm. [Beilstein 19 IV 550.]