Diamine

A diamine is an amine with exactly two amino groups. Diamines are used as monomers to prepare polyamides, polyimides, and polyureas. The term diamine refers mostly to primary diamines, as those are the most reactive.[1]

General structure of (primary) diamines. The primary amino groups (NH2) are marked blue, R is a divalent organic radical (e.g. a para-phenylene group).

In terms of quantities produced, 1,6-diaminohexane (a precursor to Nylon 6-6) is most important, followed by ethylenediamine.[2] Vicinal diamines (1,2-diamines) are a structural motif in many biological compounds and are used as ligands in coordination chemistry.[3]

Aliphatic diamines

Linear

• 1 carbon: methanediamine (diaminomethane)
• 2 carbons: ethylenediamine (1,2-diaminoethane). Related derivatives include the N-alkylated compounds, 1,1-dimethylethylenediamine, 1,2-dimethylethylenediamine, ethambutol and TMEDA.

• 
  Ethylenediamine

• 3 carbons: 1,3-diaminopropane (propane-1,3-diamine)
• 4 carbons: putrescine (butane-1,4-diamine)
• 5 carbons: cadaverine (pentane-1,5-diamine)

• 
  Cadaverine

• 6 carbons: hexamethylenediamine (hexane-1,6-diamine), trimethylhexamethylenediamine

Branched

Derivatives of ethylenediamine are prominent:

• 1,2-diaminopropane, which is chiral.
• diphenylethylenediamine, which is C₂-symmetric.
• trans-1,2-diaminocyclohexane, which is C₂-symmetric.

Cyclic

• 1,4-Diazacycloheptane

• 
  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 or MXD
• p-xylylenediamine or PXD

Aromatic diamines

Three phenylenediamines are known:[4]

• o-phenylenediamine or OPD
• m-phenylenediamine or MPD
• p-phenylenediamine or PPD. 2,5-diaminotoluene is related to PPD but contains a methyl group on the ring.

• 
  p-phenylenediamine

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:

• 4,4'-diaminobiphenyl
• 1,8-diaminonaphthalene

References

1. "Nucleophilicity Trends of Amines". Master Organic Chemistry. 2018-05-07. Retrieved 2019-08-18.
2. Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke (2005). "Amines, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a02_001.CS1 maint: uses authors parameter (link)
3. Lucet, D., Le Gall, T. and Mioskowski, C. (1998), The Chemistry of Vicinal Diamines. Angew. Chem. Int. Ed., 37: 2580–2627. doi: 10.1002/(SICI)1521-3773(19981016)37:19<2580::AID-ANIE2580>3.0.CO;2-L
4. Robert A. Smiley "Phenylene- and Toluenediamines" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_405

External links

• Diamines at the US National Library of Medicine Medical Subject Headings (MeSH)
• Synthesis of diamines