nitrosonium

Nitrosonium refers to the nitrosonium ion, NO+. It is a positively charged diatomic cation that acts as a strong nitrosating agent in inorganic and organic chemistry. In strongly acidic solutions, nitrous acid (HNO2) can generate NO+ and water, and the ion can also be supplied directly by isolable nitrosonium salts such as nitrosonium tetrafluoroborate [NO]BF4 or nitrosonium hexafluorophosphate [NO]PF6. In practice, NO+ is generated in situ for numerous transformations.

The nitrosonium ion is a potent electrophile, transferring a nitrosyl group to nucleophiles. Its chemistry centers on nitrosation reactions, notably the conversion of amines to N-nitroso derivatives and the nitrosation of thiols to form S-nitrosothiols. Reactions with alcohols or other nucleophiles can also lead to related nitroso compounds under appropriate conditions. The NO+ ion thus serves as a versatile reagent for introducing the nitroso functionality in organic synthesis.

Uses and safety considerations: Nitrosonium salts are widely used as nitrosating agents in synthetic organic chemistry and analytical applications. They enable the formation of N-nitrosamines, S-nitrosothiols, and related nitroso derivatives. Because nitrosating reactions can generate potentially hazardous or carcinogenic products in some substrates, their use requires careful control of conditions, awareness of substrate scope, and appropriate safety measures. Nitrosonium salts are typically moisture- and air-sensitive and are handled under inert or strictly anhydrous conditions.

See also: nitrosation, nitrosonium salts, N-nitrosamines.