Diamines

Diamines are organic compounds that contain two amine functional groups (two −NH2 groups) attached to a carbon framework. They are a diverse family used as building blocks in polymers, coatings, and bioactive compounds. Diamines can be aliphatic, cycloaliphatic, aromatic, or heterocyclic in structure.

Prominent examples include ethylenediamine (EDA), the simplest aliphatic diamine; hexamethylenediamine (HMD, 1,6-diaminohexane), important for nylon production; and putrescine (1,4-diaminobutane). Aromatic diamines such as para-phenylenediamine (PPD) are common in hair dyes and pigments, while piperazine is a versatile heterocyclic diamine frequently used in pharmaceutical and polymer chemistry. Diamines may have both amino groups on the same carbon skeleton or at different positions, influencing their reactivity and properties.

Diamines are typically bases due to their amino groups; they form hydrogen bonds readily and are often highly reactive in condensation reactions. Many are water-soluble and can act as bidentate ligands in coordination chemistry, forming chelate complexes with metals.

Key applications include curing agents for epoxy resins, crosslinkers with diisocyanates to make polyurethanes, and monomers for polyamides such as nylon variants. They also serve as intermediates in the production of pharmaceuticals, agrochemicals, and specialty polymers. Industrial production of diamines involves various routes, often starting from nitriles or hydrocarbons; for example, adiponitrile hydrogenation yields hexamethylenediamine used for nylon 6,6.

Safety considerations include their caustic and irritant nature; some aromatic diamines are regulated due to potential health risks. Proper handling and protective equipment are recommended.