Diamine

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 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]

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

• 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. ^{[4] [5]}

Ethylenediamine

• 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)

Cadaverine

• 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. ^[6]

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

1,4-Diazacycloheptane

• piperazine ((CH₂CH₂NH)₂)
• 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: ^[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.

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

Structure of Wurster's cation, illustrating the ability of amino substituents to stabilize arene radical cations.

Geminal diamines

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

References

1. "Nucleophilicity Trends of Amines". Master Organic Chemistry. 2018-05-07. Retrieved 2019-08-18.
2. Peter Roose; 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.pub2. ISBN   3-527-30673-0.
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. Saibabu Kotti, S. R. S.; Timmons, Cody; Li, Guigen (2006). "Vicinal Diamino Functionalities as Privileged Structural Elements in Biologically Active Compounds and Exploitation of their Synthetic Chemistry". Chemical Biology & Drug Design. 67 (2): 101–114. doi:10.1111/j.1747-0285.2006.00347.x. PMID   16492158.
5. Lucet, Denis; Le Gall, Thierry; Mioskowski, Charles (1998). "The Chemistry of Vicinal Diamines". Angewandte Chemie International Edition. 37 (19): 2580–2627. doi:10.1002/(SICI)1521-3773(19981016)37:19<2580::AID-ANIE2580>3.0.CO;2-L. PMID   29711625.
6. Dahlmann, Marc; Grub, Joachim; Löser, Eckhard (2011). "Butadiene". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–24. doi:10.1002/14356007.a04_431.pub2. ISBN   978-3-527-30673-2.
7. Robert A. Smiley "Phenylene- and Toluenediamines" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi : 10.1002/14356007.a19_405
8. Moad, Graeme; Benkovic, S. J. (1 August 1978). "On the mechanism of decomposition of geminal diamines" . Journal of the American Chemical Society. 100 (17): 5495–5499. doi:10.1021/ja00485a038. ISSN   0002-7863.
9. Aydın, Fatma; Arslan, N Burcu (5 September 2021). "Synthesis, spectral properties, crystal structure and theoretical calculations of a new geminal diamine: 2,2,2-Trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine" . Journal of Molecular Structure. 1232: 129976. doi:10.1016/j.molstruc.2021.129976.

External links

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