process comprising heating a dioxole at 100 °- 400 ° c . for a sufficient time to convert the dioxole to an epoxide , for example , bis - 2 , 2 - trifluoromethyl - 4 , 5 - difluoro - 1 , 3 - dioxole to 2 , 3 - epoxy - 3 - trifluoromethyl - 4 - trifluorobutyryl fluoride .