39. Acetaldehyde

Nomenclature

CAS number: 75-07-0
Ethanal; “aldehyde”; acetic aldehyde; ethylaldehyde.
C2H4O; mol wt 44.05.
C 54.53%, H 9.15%, O 36.32%.
CH3CHO.

Description and references

Produced by oxidation of alcohol with Na2Cr2O7 and H2SO4; usually from acetylene, dil H2SO4 and mercuric oxide as catalyst; also by passing alcohol vapor over a heated metallic catalyst. Lab procedure from ethanol: Wertheim, J. Am. Chem. Soc. 44, 2658 (1922); Fricke, Havestadt, Angew. Chem. 36, 546 (1923); Gattermann-Wieland, Praxis des Organischen Chemikers (de Gruyter, Berlin, 40th ed., 1961) p 180; from acetylene: Gattermann-Wieland, op. cit. 183; from paraldehyde: A. I. Vogel, Practical Organic Chemistry (Longmans, London, 3rd ed., 1959) p 324; by catalytic oxidation of ethylene in aq soln: J. Smidt et al., Angew. Chem. 71, 176 (1959); by oxidation of ethylene in fuel cells in the gas phase: K. Otsuka et al., Chem. Commun. 1988, 1272. Manuf: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 1-7. Toxicity data: Smyth, Arch. Ind. Hyg. Occup. Med. 4, 119 (1951). Review: H. J. Hagemeyer in Kirk-Othmer Encyclopedia of Chemical Technology vol. 1 (John Wiley & Sons, New York, 4th ed., 1991) pp 94-109.

Properties

Liquid with characteristic, pungent odor. d416 0.788. mp 123.5°. bp 21°. nD20 1.3316. Flash pt, closed cup: 36°F (38°C). Flammable. Miscible with water, alcohol. Keep cold. LD50 orally in rats: 1930 mg/kg (Smyth).

Caution

Potential symptoms of overexposure are eye, nose and throat irritation; conjunctivitis; coughing; CNS depression; eye and skin burns; dermatitis; delayed pulmonary edema. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 2. See also Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section II, p 186. This substance is reasonably anticipated to be a human carcinogen: Report on Carcinogens, Eleventh Edition (PB2005-104914, 2004) p III-1.

Use

Manuf paraldehyde, acetic acid, butanol, perfumes, flavors, aniline dyes, plastics, synthetic rubber; silvering mirrors, hardening gelatin fibers. Flavoring agent in foods and beverages. Fumigant for storage of apples and strawberries.