View source for O-Phenylenediamine

{{DISPLAYTITLE:''o''-Phenylenediamine}}
{{chembox
| verifiedrevid = 415872334
| Name = ''o''-Phenylenediamine
| ImageFile = o-phenylenediamine.png
| ImageSize = 120px
| IUPACName = Benzene-1,2-diamine
| OtherNames = ''o''-Phenylene diamine<br>1,2-Diaminobenzene<br>1,2-phenylenediamine
| Reference = <ref name=dupont>[http://www.dupont.com/specintermediates/opd.html DuPont Specialty Intermediates: o-Phenylenediamine (OPD)<!-- Bot generated title -->]</ref>
| Section1 = {{Chembox Identifiers
| Abbreviations = 
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 13837582
| InChI = 1/C6H8N2/c7-5-3-1-2-4-6(5)8/h1-4H,7-8H2
| InChIKey = GEYOCULIXLDCMW-UHFFFAOYAR
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 70582
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C6H8N2/c7-5-3-1-2-4-6(5)8/h1-4H,7-8H2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = GEYOCULIXLDCMW-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 95-54-5
| EINECS = 
| PubChem = 
| SMILES = Nc1ccccc1N
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| Section2 = {{Chembox Properties
| Formula = C<sub>6</sub>H<sub>8</sub>N<sub>2</sub>
| MolarMass = 108.1 g/mol
| Appearance =
| Density = 1.031 g/cm<sup>3</sup>
| MeltingPtCL = 102
| MeltingPtCH = 104
| Melting_notes =
| BoilingPtC = 252
| Boiling_notes = Other sources: 256 — 258 °C.
| Solubility = soluble in hot water
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| Section3 = {{Chembox Structure
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| Section4 = {{Chembox Thermochemistry
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| Section5 = {{Chembox Pharmacology
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| Section6 = {{Chembox Explosive
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| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://msds.chem.ox.ac.uk/PH/o-phenylenediamine.html Oxford MSDS]
| EUClass = Toxic (T); Dangerous for the environment (N)
| EUIndex = 
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| NFPA-H = 2
| NFPA-F = 1
| NFPA-R = 0
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| Section8 = {{Chembox Related
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}}
'''''o''-Phenylenediamine''' is a [[organic compound]] with the formula C<sub>6</sub>H<sub>4</sub>(NH<sub>2</sub>)<sub>2</sub>.  This [[aromatic]] [[diamine]] is an important precursor to many [[heterocyclic compound]]s. It is [[isomer]]ic with [[M-Phenylenediamine|''m''-phenylenediamine]] and [[P-Phenylenediamine|''p''-phenylenediamine]].

==Preparation==
Most commonly 2-nitrochlorobenzene is treated with ammonia, and the resulting 2-aminonitrobenzene is then hydrogenated:<ref name=Ullmann>Robert A. Smiley “Phenylene- and Toluenediamines” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a19_405}}</ref>
:ClC<sub>6</sub>H<sub>4</sub>NO<sub>2</sub>  +  2 NH<sub>3</sub>   →   H<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>NO<sub>2</sub>  +  NH<sub>4</sub>Cl
:H<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>NO<sub>2</sub>  +  3 H<sub>2</sub>   →   H<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>  +  2 H<sub>2</sub>O

In the laboratory, the reduction of the nitroaniline is effected with [[zinc]] powder in ethanol, followed by purification of the diamine as the hydrochloride.<ref>{{OrgSynth | author = E. L. Martin | title = ''o''-Phenylenediamine | collvol = 2 | collvolpages = 501 | prep = cv2p0501 | year = 1943}}</ref>

==Reactions and uses==
''o''-Phenylenediamine condenses with [[ketone]]s and [[aldehyde]]s to give rise to a variety of useful products.  Reactions with esters affords [[benzimidazole]]s. The herbicide [[benomyl]] is prepared in this manner. Also, [[quinoxaline]]dione 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 [[diketone]]s is used in the preparation of a variety of pharmaceuticals.<ref>See for example, {{cite journal | author = Renault, J. et al. | title = Heterocyclic quinones. Quinoxaline-5,6 and 5,8 diones, potential antitumoral agents | journal = Eur. J. Med. Chem. | year = 1981 | volume = 16 | pages = 545–550}}</ref>

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 [[imine|diimine]] derivatives, which are intensely coloured and often exist in multiple stable oxidation states.<ref>{{cite journal | author = Warren, L. F. | title = Synthesis of [M'-N<sub>4</sub>] and [M'-N<sub>6</sub>] Complexes Based on ''o''-Benzoquinone Diimine with Cobalt, Iron, and Ruthenium | journal = [[Inorg. Chem.]] | year = 1977 | volume = 16 | pages = 2814–2819 | doi = 10.1021/ic50177a028}}</ref>

==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]].<ref>{{cite book|title=Enzyme Immunoassays: From Concept to Product Development|author=Deshpande SS|page=169|year=1996|isbn=978-0412056017|publisher=Chapman &amp; Hall|location=New York}}</ref>

==References==
<references/>

{{DEFAULTSORT:Phenylenediamine, o-}}
[[Category:Polyamines]]
[[Category:Anilines]]
[[Category:Chelating agents]]

[[de:O-Phenylendiamin]]
[[it:1,2-fenilendiammina]]
[[pt:O-Fenilenodiamina]]
[[ja:O-フェニレンジアミン]]
[[fi:O-fenyleenidiamiini]]
[[zh:邻苯二胺]]