GB624604A - Improvements in or relating to esters of chloroformic acid and the preparation thereof - Google Patents

Abstract

Esters of chloroformic acid are produced by reacting a compound having an alcoholic hydroxyl group with liquid phosgene or phosgene in solution, the phosgene being present in excess of the stoichiometric amount required for reaction with the alcoholic compound, allowing unreacted phosgene to vaporize, condensing the vaporized phosgene and returning the condensed phosgene to the reaction mixture. After the reaction begins additional amounts of the alcohol and phosgene are introduced into the reactor, preferably in continuous streams, a considerable excess of phosgene being always maintained in the reaction vessel. The reaction temperature is preferably between 15 DEG and 25 DEG C. and is controlled by adjusting the relative rates at which the alcohol and phosgene are introduced, thus, if the temperature becomes too high the ratio of phosgene to alcohol is increased and vice versa. The reaction may also be effected by introducing phosgene, preferably gaseous phosgene, into a preformed quantity of the chloroformate of the alcoholic compound having phosgene dissolved therein, then introducing phosgene, preferably gaseous phosgene, together with additional alcohol at such a rate as to maintain an excess of phosgene, allowing the unreacted phosgene to vaporize, condensing the vaporized phosgene and returning it to the reaction mixture. The reaction may be carried out continuously. In examples: (1), (2) and (3) ethyl alcohol, isopropyl alcohol and allyl alcohol respectively are introduced into liquid phosgene in a glass reactor equipped with a brine cooled reflux condenser, the phosgene vapour is condensed and returned to the reactor and further amounts of the alcohol and phosgene are introduced, the flow and relative amounts of phosgene and alcohol being adjusted so as to maintain the reaction temperature between 15 DEG and 25 DEG C., ethyl, isopropyl and allyl chloroformates respectively are obtained; (4) and (5) gaseous phosgene is introduced into a reaction vessel charged with ethylene glycol bis-(chloroformate) and diethylene glycol bis-(chloroformate) respectively, and ethylene glycol or diethylene glycol then added, the temperature being controlled as in (1). Other compounds containing an alcoholic hydroxyl group which are specified are monohydric alcohols, e.g. propyl-, butyl-, isobutyl- and benzyl-alcohols; glycols such as propylene glycol, trimethylene glycol; glycerol, 2-nitro-propanol-1, methyl-tert-butyl carbinol; ethyl lactate and methyl glycollate.