Nitrowanie

Nitrowanie, or nitration, is a chemical reaction that introduces a nitro functional group (-NO2) into an organic molecule. The most common form is electrophilic aromatic substitution on aromatic rings, typically using a mixture of concentrated sulfuric acid and nitric acid to generate the nitronium ion (NO2+), the active electrophile.

In aromatic nitration, the aromatic ring acts as the nucleophile; substitution occurs with loss of a hydrogen, yielding nitro-substituted aromatic compounds such as nitrobenzene. The reaction is highly exothermic and temperature-controlled to avoid over-nitration (dinitration) and side reactions. The nitronium ion is generated by protonation and dehydration of nitric acid in the acidic medium. Alternative nitrating systems exist, including nitronium salts and organic solvent media, but the mixed acid system remains the most common.

Reactivity and regioselectivity depend on existing substituents. Benzene gives nitrobenzene in a straightforward process. Alkyl substituents (e.g., toluene) direct to ortho and para positions; electron-withdrawing substituents can direct to meta positions. Phenols or anisole are highly activated, and nitration occurs rapidly at the ortho and para positions; some meta products may appear under certain conditions, especially with deactivated rings.

Industrial relevance: Nitro compounds are important precursors. Nitrobenzene is hydrogenated to aniline, a key intermediate for polymers, dyes, and pharmaceuticals. Nitroaromatics are also used in the production of explosives such as TNT and in the manufacture of nitrocellulose, dyes, and specialty chemicals.

Safety and environmental aspects: The process uses strong acids, is highly exothermic, and can generate corrosive fumes and mixed nitrated byproducts. Proper handling, temperature control, and waste treatment are essential to minimize hazards and environmental impact.