Preparation of vicinal epoxides

A process for the preparation of a vicinal epoxide having 2 to 30 carbon atoms per molecule of the general formula ##STR6## wherein each R and each R' are individually selected from the group consisting of hydrogen and hydrocarbyl radical groups having 1 to 10 carbon atoms and wherein R' radicals in said epoxide can represent a divalent aliphatic hydrocarbon radical which together with the oxirane group in said epoxide can form a cycloaliphatic nucleus, which comprises heating the corresponding carbonate ester having the general formula ##STR7## wherein R and R' are as defined above, in the presence of a catalytic amount amount of a phosphonium halide catalyst having the general formula R".sub.4 PX, wherein R" is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkenyl, cycloalkenyl and combinations thereof having from 1 to 10 carbon atoms and X is selected from the group consisting of chlorine, bromine and iodine.