Urea-hydrogen peroxide (UHP) alone or in combination with carboxylic anhydrides has been shown to serve as a valuable alternative to anhydrous hydrogen peroxide: the range of substrates oxidised include alkenes (epoxidation), ketones (Baeyer-Villiger reaction), sulphides (to sulphones), nitrogen heterocycles (to N-oxides), and aromatic hydrocarbons (to phenols).