nitrogrupper

Nitro groups, written as -NO2, are a class of functional groups in organic chemistry. A nitro group consists of a nitrogen atom bonded to two oxygens, usually attached to a carbon skeleton. The group is typically planar and highly polar, with several resonance structures that delocalize negative charge onto the oxygens.

Chemically, the nitro group is a strong electron-withdrawing substituent due to both inductive (-I) effects and resonance (-M). This withdrawal lowers electron density on nearby atoms, influences acidity and basicity, and often deactivates reactive sites toward electrophilic attack. On aromatic rings, nitro groups are strongly deactivating and direct substitution to the meta position.

Most common entry of nitro groups into organic molecules is aromatic nitration, using nitronium ion NO2+ generated from nitric and sulfuric acids. Nitro groups also appear in aliphatic nitro compounds (R-NO2), formed by various nitrosation and oxidation processes. Nitroarenes are stable and widely used as intermediates in synthesis.

Nitro groups can be reduced to amines under catalytic hydrogenation or with metal reducing agents, giving anilines (Ar-NH2) after workup. They can also be converted to other functional groups, such as hydroxylamines or nitroso derivatives, under controlled conditions. Because of their properties, nitro groups are useful precursors in the production of dyes, pharmaceuticals, and energetic materials.

Safety notes: many nitro compounds are toxic and some nitroaromatics are sensitive explosives. Handling requires appropriate precautions and knowledge of material safety data sheets.