Styrene oxide is an epoxide derived from styrene. It can be prepared by epoxidation of styrene with peroxybenzoic acid, in the Prilezhaev reaction. Styrene oxide is slightly soluble in water. A trace amount of acid in water causes hydrolysis to racemic phenylethyleneglycol via a benzylic cation. If the amount of water is not sufficient, acid-catalyzed isomerization for phenylacetaldehyde will occur.