amiini

Amines are a class of organic compounds derived from ammonia by replacement of one or more hydrogen atoms with alkyl or aryl groups, giving primary (RNH2), secondary (R2NH), and tertiary (R3N) amines. They can also form quaternary ammonium salts (R4N+) when all hydrogen atoms of nitrogen are substituted.

A key property of amines is basicity: they accept a proton to form ammonium ions (RNH3+ or R4N+). Basicity is influenced by the nature of the substituents; aliphatic (alkyl) amines are typically more basic than aromatic ones, such as anilines, where resonance with the aromatic ring reduces the availability of the lone pair. In water, primary and secondary amines can be protonated to varying extents, while tertiary amines form stable ammonium salts but do not donate hydrogen bonds as donors.

Amines vary in solubility and physical properties with their substituents. Small amines are generally soluble in water, whereas larger, more hydrophobic amines are less so. They are versatile building blocks in organic synthesis and industry.

Preparation methods include reductive amination of carbonyl compounds, hydrogenation of nitriles or nitro compounds, and alkylation of ammonia or existing amines. The Gabriel synthesis provides a route to primary amines. Reactions of amines include acylation to form amides, condensation with carbonyls to give imines, and formation of diazonium salts from primary aryl or alkyl amines for further functionalization. Alkylation of amines yields tertiary and quaternary ammonium salts.

Applications are widespread: amines are foundational in pharmaceuticals and agrochemicals, serve as dyes (notably anilines), function in catalysis, and appear as surfactants and specialized materials. They also occur naturally in amino acids, neurotransmitters, and other biomolecules. Safety considerations include irritant and toxic properties for many amines, with quaternary salts generally less volatile but environmentally persistent.