Verfahren zur Herstellung von ª‡-Halogenalkylisocyanaten

Alkyl isocyanates having at least one halogen atom in the alpha position are obtained by reacting an alkyl isocyanate having at least one H atom in the a position, or an alkyl carbamic acid halide having at least one H atom in the a position, with a halogenating agent. Halogen gas may be flowed into an appropriate alkyl isocyanate whilst the mixture is subjected to ultra-violet light until the stoichiometric required amount of halogen has been absorbed, and thereafter the resulting halogeno alkyl isocyanate is removed by distillation. Halogen gas may be flowed into a suspension of an appropriate alkyl carbamic acid chloride while irradiating the suspension with U-V light, the reaction mixture being maintained at a temperature not exceeding 70 DEG C. during absorption of the halogen. Specified isocyanates which may be halogenated include methyl, ethyl, propyl, butyl, stearyl, cyclohexyl, b -cyanoethyl, and benzyl isocyanate; e -isocyanato p caproyl chloride; hexamethylene diisocyanate; carboxyethyl methyl isocyanate. Halogenation produces the corresponding a -mono or a -di-halogeno alkyl iso- or di-iso-cyanate. Halogeno alkyl carbamyl halides may be formed as intermediate products. These may be converted into isocyanates by heating. The halogenating agent may be chlorine, bromine, sulphuryl chloride, or sulphuryl bromide. During halogenation catalytically active halogen transfer agents such as ferric chloride may be present. Solvents may also be present. Examples describe the production of chloromethyl isocyanate, chloromethyl carbamyl chloride being formed as an intermediate and being converted to the isocyanate by heating to 120 DEG C. in a stream of nitrogen. 1.1.2.2-tetra-chloroethyl isocyanate, and a -chlorobenzyl isocyanate, and reference is made to the production of other isocyanates, including pentachloro - ethyl, a -bromo-benzyl, and a -bromo-b -chloro-ethylisocyanates, and 1.4-diisocyanato-1.4-dichlorocyclohexane. Specification 752,931 is referred to.