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 quantities produced, 1,6-diaminohexane (a precursor to Nylon 6-6) is most important, followed by ethylenediamine. Vicinal (chemistry), Vicinal diamines (1,2-diamines) are a structural motif in many biological compounds and are used as ligands in coordination chemistry.

Aliphatic diamines

Linear

* 2 carbon backbone: ethylenediamine (1,2-diaminoethane). Related derivatives include the N-alkylated compounds, 1,1-dimethylethylenediamine, 1,2-dimethylethylenediamine, ethambutol, tetrakis(dimethylamino)ethylene, TMEDA. Many 1,2-diamine derivatives are of practical interest such as penicillin. * 3 carbon backbone: 1,3-diaminopropane (propane-1,3-diamine) * 4 carbon backbone: putrescine (butane-1,4-diamine) * 5 carbon backbone: cadaverine (pentane-1,5-diamine) image:Pentane-1,5-diamine 200.svg, 120px, Cadaverine, thumb * 6 carbon backbone: hexamethylenediamine (hexane-1,6-diamine, HMD). HMD and other long chain diamines can be prepared by hydrocyanation to give dinitrile, which can be hydrogenated.

Branched

Derivatives of ethylenediamine are prominent: * 1,2-diaminopropane, which is chiral. * 2,3-Butanediamine, two diastereomers, one of which is C₂-symmetric. * Diphenylethylenediamine, two diastereomers, one of which is C₂-symmetric. * trimethylhexamethylenediamine, several isomers * 1,2-Diaminocyclohexane, two diastereomers, one of which is C₂-symmetric.

Cyclic

image:DACH.png, 1,4-Diazacycloheptane, 120px, right * piperazine () * 1,4-Diazacycloheptane

Xylylenediamines

Xylylenediamines are classified as alkylamines since the amine is not directly attached to an aromatic ring. *''o''-xylylenediamine or OXD * m-Xylylenediamine, ''m''-xylylenediamine or MXD *''p''-xylylenediamine or PXD

Aromatic diamines

Three phenylenediamines are known: * o-Phenylenediamine, ''o''-phenylenediamine or OPD * m-Phenylenediamine, ''m''-phenylenediamine or MPD * p-Phenylenediamine, ''p''-phenylenediamine or PPD. 2,5-diaminotoluene is related to PPD but contains a methyl group on the ring. image:P-phenylenediamine.svg, ''p''-phenylenediamine, 120px, thumb Various N-methylated derivatives of the phenylenediamines are known: * dimethyl-4-phenylenediamine, a reagent. * N,N'-di-2-butyl-1,4-phenylenediamine, an antioxidant. Examples with two aromatic rings include derivatives of biphenyl and naphthalene: * benzidine, 4,4'-diaminobiphenyl * 1,8-diaminonaphthalene

Geminal diamines

image:Me2NCH2NMe2.svg, 160px, Bis(dimethylamino)methane Geminal diamines (1,1-diamines) are an unusual class of diamines mainly of academic interest. Bis(dimethylamino)methane ([(CH₃)₂N]₂CH₂) is a stable example. Geminal diamines with N-H bonds are particularly rare. They are invoked as intermediates in transimination reactions and the reduction of Amidine, amidines. In aqueous conditions they preferentially eliminate the less basic amine to leave an Iminium, iminium ion. Some stable geminal diamines have been isolated. The parent gem-diamine is methylenediamine (diaminomethane), which again is mainly of theoretical interest.

References

External links

* {{MeshName, Diamines
Synthesis of diamines
Diamines, Monomers