 Using a peracid ("m"CPBA or peroxybenzoic acid), the epoxy product quickly rearranges, catalyzed by the acid byproduct of the epoxidation.Using DMDO gives the epoxide as a stable product—the byproduct of the epoxidation is neutral acetone.By varying the amount of DMDO, either the mono- or diepoxide can be formed, with the oxygen atoms "exo" on the bicyclic carbon framework.