GB485761A - Manufacture of isocyanates - Google Patents

Abstract

Isocyanates are obtained by the action of phosgene on urethanes of the type RNHCOOR1, where R is an alkyl, aryl, aralkyl or cycloalkyl group and R1 is an alkyl group. Urethanes of the type specified may be obtained by the known process wherein an alkaline alcoholic solution of a carboxylic acid amide is treated with halogen; specified amides from which urethanes may be so prepared are those of acetic, propionic, butyric, valeric, caproic, heptoic, caprylic, nonylic, capric, undecylenic, lauric, tridecylic, myristic, pentadecylic, palmitic, margaric, stearic, nondecylic, arachidic, behenic, lignoceric, cerotic, melissic, benzoic, o- and p-toluic, o- and p-methoxybenzoic, a -naphthoic, phenylacetic, phenylpropionic, o- and p-tolylacetic, hexahydrobenzoic, cyclohexylacetic, methylcyclohexylacetic, cyclohexylpropionic, naphthenic and hydroabietic acids, and also the amides of mixed acids such as are obtainable from coconut or palm-kernel oil, carnauba or montan wax, or hydrogenated fats. Suitable unethanes may also be obtained by the interaction of a primary amine and an alkyl chloroformate. Examples are given in which, by reaction with phosgene at a raised temperature in the presence or absence of a diluent, (1) N-heptadecylcarbamic acid methyl ester yields heptadecyl isocyanate; (2) N-phenylcarbamic acid methyl ester yields phenyl isocyanate; (3) N-benzylcarbamic acid methyl ester yields benzyl isocyanate; (4) N-methylcarbamic acid ethyl ester yields methyl isocyanate; (5) a mixture of N-alkylcarbamic acid esters, obtained by the action of chlorine and sodium methoxide on the amides of coconut-oil acids, yields a mixture of the corresponding alkyl isocyanates; (6) N-o-tolylcarbamic acid ethyl ester yields o-tolyl isocyanate; (7) N-p-tolylcarbamic acid methyl ester yields p-tolyl isocyanate; (8) N-cyclohexyl carbamic acid methyl ester yields cyclohexyl isocyanate.