PREPARATION OF ALKYL ISOTHIOCYANIC ESTER

Alkyl isothiocyanates of the formula R-N=C=S can be prepared by reaction of N-alkyldithiocarbamates with hydrogen peroxide in aqueous phase at 95 to 130 DEG C. According to the invention, the aqueous N-alkyldithiocarbamate solution is made to react with a 20 to 40% strength by weight aqueous hydrogen peroxide solution in a volume ratio of 1 to 0.8 to 1, while maintaining a pH of 1.5 to 4.5. Preferably, the solutions are sprayed into a reactor in which the alkyl isothiocyanate formed is distilled off in vapour form and the aqueous phase containing the by-products accumulates in the reactor. The process according to the invention makes it possible to increase the space-time yield significantly because compared with the prior art process which is carried out at pH 5 to 9 a much smaller amount of sulphur is formed, thus minimising the shutdown times for the cleaning of the reactor.