Diamine

 ( Monomers ) 

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).

A diamine is an amine with two . Diamines are used as monomers to prepare , , and . The term diamine refers mostly to 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 diamines (1,2-diamines) are a structural motif in many biological compounds and are used as ligands in coordination chemistry.

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Aliphatic diamines

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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)
• 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.
  (2025). 9783527306732 ISBN 9783527306732

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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.

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Cyclic

• piperazine ()
• 1,4-Diazacycloheptane

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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

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Aromatic diamines Three are known:Robert A. Smiley "Phenylene- and Toluenediamines" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim.

• 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 of biphenyl and naphthalene:

• benzidine
• 1,8-diaminonaphthalene

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Geminal diamines Geminal diamines (1,1-diamines) are an uncommon class of diamines mainly of academic interest. Of the few that exist, most are di-tertiary amines. Bis(dimethylamino)methane ((CH₃)₂N₂CH₂) is an isolable example.

Geminal diamines with N-H bonds are particularly rare. They are invoked as intermediates in transimination reactions and the reduction of Amidine. In aqueous conditions they preferentially eliminate the less basic amine to leave an Iminium. Some stable geminal diamines have been isolated. The parent gem-diamine is methylenediamine (diaminomethane), which again is mainly of theoretical interest.

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External links

• Synthesis of diamines

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