The nitrosation reaction consists in the replacement of a hydrogen atom by the nitroso group with the formation of a nitroso or oximo derivative. With a few exceptions, the replacement of hydrogen on an aliphatic carbon atom requires the presence of an electron-attracting groups adjacent to the carbon to be nitrosated. Acyl, aroyl, carbonyl, carboxy, carbalkoxyl, nitrogen, cyano, imino, and aryl groups may serve as activators. Monoketones are readily converted into alpha-oximino ketones, whereas monoesters containing no other activating groups do not undergo the reaction. Victor Meyer discovered the reaction in 1873–1874.