Hexamethylenediamine or hexane-1,6-diamine, is the

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula H₂N(CH₂)₆NH₂. The molecule is a

diamine A diamine is an amine with two amino groups. Diamines are used as monomers to prepare polyamides, polyimides, and polyureas. The term ''diamine'' refers mostly to Primary (chemistry), primary diamines, as those are the most reactive. In terms of ...

, consisting of a hexamethylene

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

chain terminated with

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

functional group In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...

s. The colorless solid (yellowish for some commercial samples) has a strong amine odor.

Synthesis

Hexamethylenediamine was first reported by Theodor Curtius. It is produced by the hydrogenation of

adiponitrile Adiponitrile is an organic compound with the chemical formula (CH2)4(CN)2. This viscous, colourless dinitrile is an important precursor to the polymer nylon 66. In 2005, about one million tonnes of adiponitrile were produced.M. T. Musser, "Adipi ...

: :NC(CH₂)₄CN + 4 H₂ → H₂N(CH₂)₆NH₂ The hydrogenation is conducted on molten

diluted with

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

, typical catalysts being based on

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

and

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

. 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-diaminocyclohexane, hexamethyleneimine, and the triamine bis(hexamethylenetriamine). An alternative process uses

Raney nickel Raney nickel , also called spongy nickel, is a fine-grained solid composed mostly of nickel derived from a nickel–aluminium alloy. Several grades are known, of which most are gray solids. Some are pyrophoric, but most are used as air-stable s ...

as the catalyst and adiponitrile that is diluted with hexamethylenediamine itself (as the solvent). This process operates without ammonia and at lower pressure and temperature.Robert A. Smiley "Hexamethylenediamine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.

Applications

Hexamethylenediamine is used almost exclusively for the production of

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s, 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 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing six carbon at ...

via condensation with

adipic acid Adipic acid or hexanedioic acid is the organic compound with the formula C6H10O4. It a white crystalline powder at standard temperature and pressure. From an industrial perspective, it is the most important dicarboxylic acid at about 2.5 billion ...

. Otherwise

hexamethylene diisocyanate Hexamethylene diisocyanate (HDI) is the organic compound with the formula (CH2)6(NCO)2. It is classified as an diisocyanate. It is a colorless liquid. It has sometimes been called HMDI but this not usually done to avoid confusion with Hydrogenate ...

(HDI) is generated from this diamine by phosgenation as a monomer feedstock in the production of

polyurethane Polyurethane (; often abbreviated PUR and PU) is a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane term ...

. The diamine also serves as a

cross-link In chemistry and biology, a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...

ing agent in

epoxy resin Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also co ...

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 BASF SE (), an initialism of its original name , is a European Multinational corporation, multinational company and the List of largest chemical producers, largest chemical producer in the world. Its headquarters are located in Ludwigshafen, Ge ...

site in

Seal Sands Seal Sands () is a 294.37 hectare biological Site of Special Scientific Interest in County Durham, England, notified in 1966. Situated in the mouth of the River Tees next to Greatham Creek and Seaton-on-Tees Channel, the site is accessible fr ...

, near

Billingham Billingham is a List of towns in England, town and Civil parishes in England, civil parish in County Durham, England. The town is on the north side of the River Tees and is governed as part of the Borough of Stockton-on-Tees unitary authority ...

(UK) on 4 January 2007 in which 37 persons were injured, one of them seriously.BBC News
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References

{{Reflist Monomers Diamines

Synthesis

Applications

Safety

See also

References