Nomenclature
CAS number: 624-83-9
Isocyanatomethane; isocyanic acid methyl ester; MIC.
C
2H
3NO; mol wt 57.05.
C 42.11%, H 5.30%, N 24.55%, O 28.04%.
CH
3N=C=O.
Description and references
Intermediate in the manufacture of insecticides
and herbicides including carbaryl, q.v. Prepn via Curtius rearrangement: J. W. Boehmer, Rec. Trav. Chim. 55, 379 (1933);
by heating N,N-diphenyl-N′-methylurea: W. Siefken, Ann. 562, 75 (1949); by phosgenation
of bis(trimethylsilyl)methylamine: V. F. Mironov et al., Zh. Obshch. Khim. 39, 2598 (1969). Used in prepn of α-aryl-β-methylureas: J. W. Boehmer, loc. cit.; of semicarbazides: Ch. C. P. Pacilly, Rec. Trav. Chim. 55, 101 (1936);
in conversion of aldoximes to nitriles: J. A. Albright, M. L. Alexander, Org. Prep. Proced. Int. 4, 215
(1972). Toxicity of vapor to rats, mice, humans; physical properties:
G. Kimmerle, A. Eben, Arch. Toxicol. 20, 235 (1960). Uptake and distribution studies in animals:
J. S. Ferguson et al., Toxicol.
Appl. Pharmacol. 94, 104 (1988). Acute oral
toxicity: E. H. Vernot et al., ibid. 42, 417 (1977).
Properties
Liquid, bp 39-40°. d20 0.96. Poisonous; flammable. Vapor press. at 4.2°: 200 torr; at 13.5°: 300 torr; at 20.6°:
400 torr; at 31.2°: 600 torr. LD50 in male rats (mg/kg): 140 single oral dose (Vernot). LC50 in rats (4 hours exposure to
vapor): 5 ppm (Kimmerle, Eben).Note
An industrial accident during the manufacture
of carbaryl in Bhopal, India on December 3, 1984 resulted in the leakage
of an unknown amount of methyl isocyanate into the air. Over 2,000
people died and an estimated 200,000 were exposed to the vapor: Chem. Eng. News 62, 6 (Dec. 10,
1984); ibid. 63, 14
(Feb. 11, 1985). Series of articles on follow-up studies on survivors:
Indian J. Exp. Biol. 26, 149-176, 201-204 (1988). Review of human toxicity: P. S. Mehta et al., J. Am. Med. Assoc. 264, 2781-2787 (1990).Caution
Potential symptoms of overexposure
are irritation of eyes, skin, nose and throat; respiratory sensitization;
coughing, pulmonary secretions, chest pain and dyspnea; asthma;
eye and skin injury. See NIOSH
Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997)
p 212. Highly volatile. Exposure to 2 ppm for 1-5 min produced tears
and irritation of the nose and throat (Kimmerle, Eben).Use
In organic synthesis; in manufacture of carbamate
pesticides.