aminés

Amines are organic compounds derived from ammonia by replacing one or more hydrogen atoms with alkyl or aryl groups. They are commonly classified by the number of carbon substituents on the nitrogen: primary amines (RNH2), secondary amines (R2NH), and tertiary amines (R3N). When a tertiary amine is further alkylated, quaternary ammonium salts (R4N+) are formed.

Amines can be aliphatic (alkyl or cycloalkyl substituents) or aromatic, with aniline-type structures where the amino group is attached to an aryl ring. The lone pair on nitrogen makes amines basic and nucleophilic; they form ammonium salts upon protonation or with acids. Aliphatic amines are typically more basic than aromatic amines due to resonance stabilization in anilines.

Common preparation methods include: reduction of nitro compounds; reductive amination of carbonyl compounds with ammonia or primary/secondary amines; catalytic hydrogenation of nitriles to primary amines; the Gabriel synthesis for primary amines; and alkylation of ammonia or existing amines to give higher-substituted amines. Dehydration and Hofmann rearrangement are also related transformations.

Applications: amines are key intermediates in the manufacture of pharmaceuticals, agrochemicals, dyes, and polymers. Anilines are important in dye production; tertiary amines and quaternary ammonium salts serve as bases, catalysts, or surfactants in various chemical processes. Amines are also used as ligands in coordination chemistry.

Safety: many amines are corrosive or irritant and can be toxic if inhaled or absorbed; proper ventilation, containment, and protective equipment are required during handling. Some amines have strong odors and environmental concerns due to persistence or toxicity.