Aliphatic mono-isocyanate prodn. - by reacting carbamoyl chloride and active hydrogen cpd., then thermal decomposition, of the adduct

摘要

Prepn. of isocyanates of formula R-NCO (I) (R = 1-4C aliphatic hydrocarbyl, opt. olefinically unsatd) comprises reacting the carbamoyl chlorides RNH. COC1 (II) with cpds. contg. >=1 active H atom, in an inert solvent. HCl is eliminated during the reaction and an addition cpd. of (I) with (III) is formed. This adduct is then decomposed by heating to give (I) and (III) which are sepd. simultaneously by distn. Pref. (III) are amides of sulphuric acid or of organic sulphonic acids contg. the gp. -SO2NHR1 (R1 = aliphatic hydrocarbyl); phenols having >=1 electrophilic substit. to increase the acidity of the OH gp; or organic cpds. with >=1 -NH.CO.O-function. (I) re intermediates for plant-protection agents and pharmaceuticals. Reserve reaction between HCl and (I) is completely prevented, so high yields of high purity (I) are achieved without large investments in condensers etc.