NitrosoGruppe

The nitroso group is a functional group in organic chemistry defined by the presence of a nitroso moiety (-NO) attached to the rest of the molecule via the nitrogen atom. In common notation it appears as R–NO, where R represents the remainder of the compound. The nitrogen–oxygen bond has substantial multiple-bond character, and resonance forms place charge distribution between N and O. The group can be found in two broad classes of compounds: simple nitrosyl derivatives with a single nitrogen bound to the carbon skeleton (R–NO) and N-nitroso compounds in which the nitrogen bears two substituents (R2N–NO).

Nitroso compounds occur in several forms. Aryl and alkyl nitroso compounds have the nitroso group directly attached to an aromatic ring or alkyl chain, for example nitrosobenzene (Ph–NO). N-nitroso compounds feature an N–N bond arrangement where a second substituent is attached to the nitrogen, such as N-nitrosamines (R2N–NO). These different arrangements influence properties such as stability, reactivity, and susceptibility to reduction or rearrangement.

Preparation and occurrence: The nitroso group is typically introduced by nitrosation, using nitrous acid generated in situ from nitrite salts and acid, or by reactions with nitrosylating reagents. Nitroso compounds can arise as intermediates in organic synthesis and can be encountered in environmental and biological contexts, where they may release reactive species such as nitric oxide under certain conditions.

Reactivity, applications, and safety: Nitroso compounds are versatile intermediates in synthesis, enabling transformations such as nitroso-ene reactions and various coupling strategies. They can be reduced to hydroxylamines or amines or rearranged under specific conditions. However, many N-nitroso compounds, particularly nitrosamines, are of toxicological concern due to carcinogenic potential, necessitating careful handling and control of exposure.