Title: Diazomethane
CAS Registry Number: 334-88-3
Additional Names: Azimethylene
Molecular Formula: CH2N2
Molecular Weight: 42.04
Percent Composition: C 28.57%, H 4.80%, N 66.64%
Line Formula: CH2=N+=N-
Literature References: Prepd from chloroform and hydrazine by reaction with potassium hydroxide: Staudinger, Kupfer, Ber. 45, 501 (1912); McManus et al., J. Org. Chem. 33, 4272 (1968); from KOH and nitrosomethylurea: Dessaux, Durand, Bull. Soc. Chim. Fr. 1963, 41. These methods yield gaseous diazomethane. The following procedures yield ether solns of diazomethane. From N-nitroso-b-methylaminoisobutyl methyl ketone in ether and isopropanol by reaction with sodium isopropoxide or from the same ketone in ether by reaction with sodium cyclohexoxide: Redemann et al., Org. Synth. 25, 28 (1945). By KOH saponification of nitrosomethylurea in ether: Arndt, Org. Synth. coll. vol. II, 165 (1943), or of nitrosomethylurethan in ether: von Pechmann, Ber. 27, 1888 (1894); 28, 855 (1895); Meerwein, Burneleit, Ber. 61, 1845 (1928). In the laboratory diazomethane may be prepd most simply by the action of alkali on the commercially available N-methyl-N-nitroso-N¢-nitroguanidine, cf. McKay, J. Am. Chem. Soc. 70, 1974 (1948); McKay et al., Can. J. Res. 28, 683 (1950); Fieser and Fieser, Organic Chemistry (Reinhold, New York, 3rd ed., 1956) p 176. Alternate intermediate: p-tolylsulfonylmethylnitrosamide ("Diazald" Aldrich Chemical Co.), see De Boer, Backer, Org. Synth. coll. vol. IV, 250 (1963).
Properties: Very toxic yellow gas. Explosive! Use safety screen. Insidious poison, a well-ventilated hood is absolutely necessary, avoid vapor. mp -145°; bp -23°. Undil liq and concd solns may explode violently, especially if impurities are present. Gaseous diazomethane may explode on heating to 100° or on rough glass surfaces. Ground glass apparatus and glass stirrers with glass sleeve bearings where grinding may occur, should not be used. Alkali metals also produce explosions with diazomethane. Sol in ether, dioxane. Such solns dec only slowly at low temps. Decompn is more rapid if alcohols or water are present. Copper powder causes active decompn with the evolution of nitrogen and the formation of insol white flakes of polymethylene (CH2)x. Solid calcium chloride or boiling stones have the same effect. This phenomenon appears to occur always during the action of diazomethane on solid substances.
Melting point: mp -145°
Boiling point: bp -23°
CAUTION: Potential symptoms of overexposure are eye irritation; coughing, shortness of breath; headache; fatigue, flushing of skin, fever; chest pain, pulmonary edema, pneumonitis; asthma; direct contact with liquid may cause frostbite. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 92. May act as a respiratory sensitizer. See Patty's Industrial Hygiene and Toxicology vol. 2A, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 3rd ed., 1981) pp 2784-2786.
Use: Powerful methylating agent for acidic compds such as carboxylic acids, phenols, enols. For syntheses with diazomethane see the reviews by Smith, Chem. Rev. 23, 193 (1938); Eistert, Z. Angew. Chem. 54, 99, 124 (1941) translated by Spangler in Newer Methods of Preparative Organic Chemistry (New York, 1948) p 513; J. S. Pizey, Synthetic Reagents vol. 2 (John Wiley, New York, 1974) pp 65-142.

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