Diamine

Practical considerations

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. Many diamines are used as hardeners in the curing of epoxide resins. Putrescine and cadaverine are simple diamines that occur widely in nature.

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) right|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

thumb|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 or MXD
• p-xylylenediamine or PXD

Aromatic diamines

Three phenylenediamines are known:

• 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|120px|right|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:
• 4,4'-diaminobiphenyl
• 1,8-diaminonaphthalene

Geminal diamines

thumb|right|160px|Bis(dimethylamino)methane 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)2N]2CH2) 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 amidines. In aqueous conditions they preferentially eliminate the less basic amine to leave an iminium ion. Some stable geminal diamines have been isolated. The parent gem-diamine is methylenediamine (diaminomethane), which again is mainly of theoretical interest.

References

References

1. (1998). "The Chemistry of Vicinal Diamines". Angewandte Chemie International Edition.
2. (2018-05-07). "Nucleophilicity Trends of Amines".
3. Peter Roose. (2005). "Amines, Aliphatic". Wiley-VCH.
4. (1998). "The Chemistry of Vicinal Diamines". Angewandte Chemie International Edition.
5. (2006). "Vicinal Diamino Functionalities as Privileged Structural Elements in Biologically Active Compounds and Exploitation of their Synthetic Chemistry". Chemical Biology & Drug Design.
6. (1998). "The Chemistry of Vicinal Diamines". Angewandte Chemie International Edition.
7. (2011). "Ullmann's Encyclopedia of Industrial Chemistry".
8. Robert A. Smiley "Phenylene- and Toluenediamines" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. {{doi. 10.1002/14356007.a19_405
9. (1 August 1978). "On the mechanism of decomposition of geminal diamines". Journal of the American Chemical Society.
10. (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.