Hexamethylenediamine


Hexamethylenediamine is the organic compound with the formula H2N6NH2. The molecule is a diamine, consisting of a hexamethylene hydrocarbon chain terminated with amine functional groups. The colorless solid has a strong amine odor. About 1 billion kilograms are produced annually.

Synthesis

Hexamethylenediamine was first reported by Theodor Curtius. It is produced by the hydrogenation of adiponitrile:
The hydrogenation is conducted on molten adiponitrile diluted with ammonia, typical catalysts being based on cobalt and iron. The yield is good, but commercially significant side products are generated by virtue of reactivity of partially hydrogenated intermediates. These other products include 1,2-Cyclohexanediamine, hexamethyleneimine, and the triamine bis.
An alternative process uses Raney nickel as the catalyst and adiponitrile that is diluted with hexamethylenediamine itself. This process operates without ammonia and at lower pressure and temperature.

Applications

Hexamethylenediamine is used almost exclusively for the production of polymers, an application that takes advantage of its structure. It is difunctional in terms of the amine groups and tetra functional with respect to the amine hydrogens. The great majority of the diamine is consumed by the production of nylon 66 via condensation with adipic acid. Otherwise hexamethylene diisocyanate is generated from this diamine by Phosgenation as a monomer feedstock in the production of polyurethane. The diamine also serves as a cross-linking agent in epoxy resins.

Safety

Hexamethylenediamine is moderately toxic, with of 792–1127 mg/kg. Nonetheless, like other basic amines, it can cause serious burns and severe irritation. Such injuries were observed in the accident at the BASF site in Seal Sands, near Billingham on 4 January 2007 in which 37 persons were injured, one of them seriously.

Stability

Hexamethylenediamine is stable in air but combustible. It is incompatible with strong oxidants.