Hexamethylenediamine
Encyclopedia
Hexamethylenediamine is the organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula H2N(CH2)6NH2. The molecule is a diamine
Diamine
A diamine is a type of polyamine with exactly two amino groups. Diamines are mainly used as monomers to prepare polyamides, polyimides and polyureas. In terms of quantities produced, 1,6-diaminohexane, a precursor to Nylon 6-6, is most important, followed by ethylenediamine...

, consisting of a hexamethylene
Hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...

 hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 chain terminated with amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

 functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

s. The colorless solid (yellowish for some commercial samples) has a strong amine odor, similar to piperidine
Piperidine
Piperidine is an organic compound with the molecular formula 5NH. This heterocyclic amine consists of a six-membered ring containing five methylene units and one nitrogen atom...

. About 1 billion kilograms are produced annually.

Synthesis

Hexamethylenediamine was first reported by Theodor Curtius
Theodor Curtius
- External links :* * * *...

. It is presently produced by the hydrogenation of adiponitrile
Adiponitrile
Adiponitrile is the organic compound with the formula 42. This dinitrile, a viscous, colourless liquid, is an important precursor to the polymer nylon 66. In 2005, about one billion kilograms were produced annually.-Early routes:...

:
NC(CH2)4CN + 4 H2 → H2N(CH2)6NH2

The hydrogenation is conducted molten adiponitrile
Adiponitrile
Adiponitrile is the organic compound with the formula 42. This dinitrile, a viscous, colourless liquid, is an important precursor to the polymer nylon 66. In 2005, about one billion kilograms were produced annually.-Early routes:...

 diluted with ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, typical catalysts being based on cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

 and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

. 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).

Applications

Hexamethylenediamine is used almost exclusively for the production of polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

s, an application that takes advantage of its bifunctional structure. The great majority of the diamine is consumed by the production of nylon 6-6
Nylon 6-6
Nylon 6-6, also referred to as nylon 6,6, is a type of nylon. Nylon comes in many types, the two most common for textile and plastics industries are: nylon 6 and nylon 6,6.- Composition :...

 via condensation with adipic acid
Adipic acid
Adipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...

. Otherwise hexamethylene diisocyanate
Hexamethylene diisocyanate
Hexamethylene diisocyanate is an organic compound in the class known as isocyanates. More specifically, it is an aliphatic diisocyanate. It is produced in relatively small quantities, accounting for only 3.4% of the global diisocyanate market in the year 2000...

 (HDI) is generated from this diamine as a monomer feedstock in the production of polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

. The diamine also serves as a cross-link
Cross-link
Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...

ing 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
BASF
BASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...

 site in Seal Sands
Seal Sands
Seal Sands is a 294.37 hectare biological Site of Special Scientific Interest in Cleveland, England, notified in 1966.Situated in the mouth of the River Tees next to Greatham Creek and Seaton-on-Tees Channel, and accessible from the A178 road running between Seaton Carew and Port Clarence.- Source...

, near Billingham
Billingham
Billingham is a town in the unitary authority of Stockton on Tees, in north east England, with a population of 35,765 . It was founded circa 650 by a group of Saxons known as Billa's people, which is where the name Billingham is thought to have originated...

 (UK) on 4 January, 2007. 37 injured and 16 seriously injured.

Stability

Hexamethylenediamine is stable in air but combustible. Like all organic compounds, it is incompatible with strong oxidants.
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