Nitrosationen

Nitrosation is the chemical process by which a nitroso group (–NO) is introduced into a molecule. In organic chemistry, it most often refers to the formation of N-nitroso, O-nitroso, or S-nitroso derivatives through reaction with nitrosating agents such as nitrous acid (HNO2) or the nitrosonium ion (NO+).

In typical N-nitrosation, a nitroso group is added to nitrogen atoms, for example converting secondary amines into N-nitrosamines (R2NH + HNO2 → R2N–NO + H2O). Nitrosation can also occur at sulfur atoms, yielding S-nitrosothiols (RSH + HNO2 → RSNO + H2O). Alcohols can be nitrosated to form alkyl nitrites (ROH + HNO2 → RO–NO + H2O) under suitable conditions. In many cases, nitrosating agents are generated in situ from nitrite salts (such as NaNO2) in acidic media, which produces the electrophilic nitrosonium species responsible for the reaction.

Applications and scope: Nitrosation is used in organic synthesis to prepare N-nitroso compounds, which can serve as intermediates in further transformations, including diazotization and radical reactions. In biochemistry, nitrosation is relevant to the formation of S-nitrosothiols and other nitrogen-containing species involved in signaling pathways and nitrosative stress. Endogenous nitrosating processes can occur under physiological or gastric conditions, linking nitrosation to both normal metabolism and potential health risks.

Safety and considerations: Some N-nitrosamines are carcinogenic, and nitrosation reactions can generate reactive or toxic species. Reactions are typically performed under controlled pH, temperature, and reagent concentrations to minimize unwanted side products and health hazards.