o-Phenylenediamine
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| Names | |
|---|---|
| IUPAC name
Benzene-1,2-diamine
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| Other names
o-Phenylene diamine
1,2-Diaminobenzene 1,2-phenylenediamine | |
| Identifiers | |
3D model (JSmol)
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| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.002.210 |
CompTox Dashboard (EPA)
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| Properties | |
| C6H8N2 | |
| Molar mass | 108.1 g/mol |
| Density | 1.031 g/cm3 |
| Boiling point | 252 °C (486 °F; 525 K) |
| soluble in hot water | |
| Hazards | |
| NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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o-Phenylenediamine is a organic compound with the formula C6H4(NH2)2. This aromatic diamine is an important precursor to many heterocyclic compounds. It is isomeric with m-phenylenediamine and p-phenylenediamine.
Preparation
Most commonly 2-nitrochlorobenzene is treated with ammonia, and the resulting 2-aminonitrobenzene is then hydrogenated:[2]
- ClC6H4NO2 + 2 NH3 → H2NC6H4NO2 + NH4Cl
- H2NC6H4NO2 + 3 H2 → H2NC6H4NH2 + 2 H2O
In the laboratory, the reduction of the nitroaniline is effected with zinc powder in ethanol, followed by purification of the diamine as the hydrochloride.[3]
Reactions and uses
o-Phenylenediamine condenses with ketones and aldehydes to give rise to a variety of useful products. Reactions with esters affords benzimidazoles. The herbicide benomyl is prepared in this manner. Also, quinoxalinedione may be prepared by condensation of o-phenylenediamine with dimethyl oxalate. Condensation with xanthate esters affords mercaptoimidazoles, which are used as antioxidants in rubber products. Treatment with nitrous acid give benzotriazole, a corrosion inhibitor. Condensation of subtituted o-phenylenediamine with various diketones is used in the preparation of a variety of pharmaceuticals.[4]
In coordination chemistry, phenylenediamine is an important ligand precursor. Schiff base derivatives, such as those derived from salicylaldehyde, are excellent chelating ligands. Oxidation of its metal-phenylenediamine complexes affords the diimine derivatives, which are intensely coloured and often exist in multiple stable oxidation states.[5]
Safety
With an LD50 of 44 mg/L (aquatic), o-phenylenediamine is about 1000 times less toxic than the para-isomer. Anilines are typically handled as if they are carcinogenic. For many applications, OPD has been replaced by safer alternatives such as 3,3',5,5'-tetramethylbenzidine.[6]
References
- ^ DuPont Specialty Intermediates: o-Phenylenediamine (OPD)
- ^ Robert A. Smiley “Phenylene- and Toluenediamines” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_405
- ^ E. L. Martin (1943). "o-Phenylenediamine". Organic Syntheses; Collected Volumes, vol. 2, p. 501.
- ^ See for example, Renault, J.; et al. (1981). "Heterocyclic quinones. Quinoxaline-5,6 and 5,8 diones, potential antitumoral agents". Eur. J. Med. Chem. 16: 545–550.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ Warren, L. F. (1977). "Synthesis of [M'-N4] and [M'-N6] Complexes Based on o-Benzoquinone Diimine with Cobalt, Iron, and Ruthenium". Inorg. Chem. 16: 2814–2819. doi:10.1021/ic50177a028.
- ^ Deshpande SS (1996). Enzyme Immunoassays: From Concept to Product Development. New York: Chapman & Hall. p. 169. ISBN 978-0412056017.