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.