Almost all amine oxides are prepared by the oxidation of either tertiary aliphatic amines or aromatic N-heterocycles. Hydrogen peroxide is the most common reagent both industrially and in academia, however peracids are also important. More specialised oxidising agents can see niche use, for instance Caros acid or m'CPBA. Spontaneous or catalysed reactions using molecular oxygen are rare. Certain other reactions will also produce amine oxides, such as the retro-Cope elimination, however they are rarely employed.