PhNO

PhNO is the shorthand commonly used in organic chemistry to denote nitrosobenzene, a simple aryl nitroso compound with the formula C6H5NO. The structure consists of a benzene ring bearing a nitroso substituent (-NO), typically represented as Ph–N=O. Nitrosobenzene is generally a colorless to pale yellow liquid at room temperature and is soluble in many organic solvents, with limited water solubility.

In chemical reactivity, PhNO acts as an electrophile and participates in a range of reactions characteristic of aryl nitroso compounds. It is employed as a nitroso source in synthetic sequences and can undergo reductions to give phenylhydroxylamine, which itself is a versatile intermediate for further transformations. Nitrosobenzene can participate in nitroso–ene reactions, condensation processes, and formation of various heterocycles and azo derivatives under appropriate conditions. Because of its reactivity, PhNO is typically used in well-controlled, designed reaction schemes rather than as a general-purpose reagent.

Preparation and handling in laboratory contexts are generally described at a high level. PhNO can be prepared via oxidation of phenylhydroxylamine or through other routes from aniline derivatives that install the nitroso group, with care taken to control oxidation state and purity. Storage requires a tightly closed container, protection from light, and a cool environment to minimize decomposition. Handling should be conducted in a fume hood using appropriate personal protective equipment due to irritant and reactive nature.

Safety and regulatory notes: nitrosobenzenes are reactive and can irritate skin, eyes, and the respiratory tract. They should be used with proper ventilation and appropriate safety protocols. Related compounds include other aryl nitroso derivatives and phenylhydroxylamine.