56. Acetic Anhydride

Nomenclature

CAS number: 108-24-7
Acetic acid 1,1′-anhydride; acetic oxide; acetyl oxide; ethanoic anhydride.
C4H6O3; mol wt 102.09.
C 47.06%, H 5.92%, O 47.02%.

Description and references

Equivalent to 117.64% acetic acid. Made formerly from sodium acetate and acetyl or sulfuryl chloride; can be obtained from acetaldehyde or acetic acid: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 16-20. Of industrial importance is also the ketene process, starting with the thermal decompn of acetone: Schmidlin, Bergmann, Ber. 43, 2821 (1910). Review of bulk manufacturing process: V. H. Agreda et al., Chemtech 22, 172-181 (1992). Toxicity study: H. F. Smyth et al., Arch. Ind. Hyg. Occup. Med. 4, 119 (1951). Review of synthetic uses: D. H. Kim, J. Heterocycl. Chem. 13, 179-194 (1976); G. B. Baker et al., J. Pharmacol. Toxicol. Methods 31, 141-148 (1994).

Chemical structure

Properties

Very refractive liquid; strong acetic odor. Flammable, corrosive and combustible. Reacts with alcohol, oxidizing materials, alkaline materials. Flash pt, closed cup: 120°F (49°C). d415 1.080. mp 73°. bp 139°. nD20 1.3904. Slowly sol in water, forming acetic acid; with alcohol forms ethyl acetate; sol in chloroform, ether. LD50 orally in rats: 1.78 g/kg (Smyth).

Caution

Potential symptoms of overexposure are conjunctivitis, lacrimation, corneal edema, opacity and photophobia; nasal, pharyngeal irritation; cough, dyspnea and bronchitis; skin burns, vesiculation and sensitization dermatitis. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 2.

Use

Manuf acetyl compounds, cellulose acetates. As acetulizer and solvent in examining wool fat, glycerol, fatty and volatile oils, resins; detection of rosin. Widely used in organic syntheses, e.g., as dehydrating agent in nitrations, sulfonations and other reactions where removal of water is necessary. In prepn of anhydrous acetic acid in nonaqueous titrimetry.