A reducible unsaturated organic compound is reduced with diimide in an aqueous emulsion comprised of water, an organic phase which contains the compound to be reduced, and an effective stabilizing amount of an anionic surfactant. The organic compound is preferably an unsaturated organic compound containing a carbon-to-carbon multiple bond, which is preferably a carbon-to-carbon double bond. Diimide is formed by reaction of hydrazine with an oxidant in the aqueous emulsion described above. The preferred oxidant is hydrogen peroxide. A product is obtained in high yield and purity in most cases. This process is especially useful for the selective reduction of a compound having two or more carbon-to-carbon double bonds of different reactivities or a carbon-to-carbon double bond and a functionality (e.g., an O--O or S--S linkage) which is reducible by catalytic hydrogenation but not diimide.