URETHANE, NH2CO2C2H5, the ethyl ester of carbamic acid, is synthesized from ammonia and chlorcarbonic ester or diethyl carbonate; by prolonged boiling of urea with alcohol (A. W. Hofmann, Ber., 1871, 4, p. 268); by the action of alcoholic hydrochloric acid on cyanogen; by the action of alcohol on urea chloride (L. Gattermann, Ann., 1888, 244, p. 40); and by warming alcoholic hydrochloric acid with an alcoholic solution of potassium cyanate (O. Folin, Amer. Chem. Jour., 1897, 19, p. 341). It crystallizes in large plates, readily soluble in water and melting at 49–50° C. When heated with ammonia to 180° C., it gives urea. Cold alcoholic potash decomposes it into potassium cyanate and alcohol.
Nitroso-urethane, NO·NH·CO2C2H5, formed by reducing ammonium nitro-urethane with zinc dust and glacial acetic acid (J. Thiele, Ann., 1895, 288, p. 304), crystallizes in needles which melt at 51–52° C. (with decomposition). It is decomposed by alkalis and by acids:
| C3H6N2O3 = | CO2+C2H5OH+N2 | (alkalis), |
| 2C3H6N2O3 = 2 | CO2+C2H5OH+2N2+H2O+C2H4 | (acids). |
On oxidation it yields nitro-urethane. With a methyl alcoholic solution of potash it yields a yellow precipitate, which is probably the potassium salt of nitrosocarbamic acid, NK·NO·CO2K. Nitrourethane, NO2·NH·CO2C2H5, formed by dissolving urethane in concentrated sulphuric acid and adding ethyl nitrate to the well-cooled mixture (J. Thiele, ibid.), crystallizes in plates which melt at 64° C. and is soluble in water. It has a strongly acid reaction, its salts, however, being neutral. Its silver salt with methyl iodide gives a methyl ether, which is readily split by ammonia into methyl nitramine and methyl urethane (cf. A. P. Franchimont, Rec. trav. chim., 1894, 13, p. 309). On reduction with zinc dust and acetic acid it yields hydrazine carboxylic ester. Phenyl urethena, C6H5NH·CO2C2H5, is formed by the action of cyanformic ester on aniline at 100° C.; by the action of absolute alcohol on benzoyl azoimide (T. Curtius, Jour. prak. Chem. [2], 52, p. 214); and by the action of bromine and sodium ethylate on benzamide (E. Jeffreys, Amer. Chem. Jour., 1899, 22, p. 41). It crystallizes in long needles which melt at 51–52° C. and boil at 227–228° C. (with partial decomposition). It is easily soluble in alcohol and when heated in a sealed tube yields aniline and urea. With phosphorus pentasulphide it yields phenyl mustard oil.
Physiologically urethane has a rapid hypnotic action, producing a calm sleep and having no depressant effect on the circulation. It is much used as an anaesthetic for animals. Di-urethane, NH(CO2C2H5)2, and hedonal, NH2CO2CH(CH3)·(C3H7), are also narcotics, the latter being, in addition, a powerful diuretic. Phenyl urethane or euphorin has a physiological action more like that of acetanilide and phenacetin than of urethane. It depresses the temperature and is an analgesic. It is of little value as an hypnotic.