General structure of (primary) diamines. Theprimary amino groups (NH2) are markedblue, R is a divalent organic radical (e.g. apara-phenylene group).

Adiamine is anamine with twoamino groups. Diamines are used asmonomers to preparepolyamides,polyimides, andpolyureas. The termdiamine refers mostly toprimary diamines, as those are the most reactive.^[1]

In terms of quantities produced,1,6-diaminohexane (a precursor toNylon 6-6) is most important, followed byethylenediamine.^[2]Vicinal diamines (1,2-diamines) are a structural motif in many biological compounds and are used asligands incoordination chemistry.^[3]

• 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 aspenicillin.^[4][5]

• 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)

• 6 carbon backbone:hexamethylenediamine (hexane-1,6-diamine, HMD). HMD and other long chain diamines can be prepared byhydrocyanation to give dinitrile, which can be hydrogenated.^[6]

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.

• piperazine ((CH₂CH₂NH)₂)
• 1,4-Diazacycloheptane

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

Threephenylenediamines are known:^[7]

• 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.

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 ofbiphenyl andnaphthalene:

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

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 ofamidines. In aqueous conditions they preferentially eliminate the less basic amine to leave animinium ion.^[8] Some stable geminal diamines have been isolated.^[9] The parent gem-diamine ismethylenediamine (diaminomethane), which again is mainly of theoretical interest.

• Diamines at the U.S. National Library of MedicineMedical Subject Headings (MeSH)
• Synthesis of diamines

• Diamines
• Monomers