F2 reacts with water and CH3CN, apparently to produce the relatively stable complex HOF-CH3CN. This is probably the best known oxygen-transfer reagent and can epoxidize olefins quickly and efficiently. Various types of alkenes including aliphatic, benzylic, enones, dienones, maleates, and fumarates have been examined, and all react with the reagent to produce the corresponding mono- or diepoxides in good to excellent yields. This epoxidation is fully stereospecific, and the configuration of the starting olefin is fully retained in the resulting oxirane. In cases where exceptionally stable oxocarbocations can be formed as in 1,1-diphenylethene, the reaction produces vicinal glycols in good yields. Since the origin of the epoxides' oxygen is in the water, this method is very suitable for introducing the isotopes 170 and 180 into various molecules.