View source for P-Phenylenediamine

{{DISPLAYTITLE:''p''-Phenylenediamine}}
{{chembox
| verifiedrevid = 303384938
| ImageFile = P-phenylenediamine.png
| ImageSize = 
| Name = ''p''-Phenylenediamine
| IUPACName = 1,4-diaminobenzene
| OtherNames = paraphenylenediamine,      1,4-diaminobenzene,      1,4-phenylenediamine 
| Section1 = {{Chembox Identifiers
|   CASNo_Ref = {{cascite}}
| CASNo = 106-50-3
|   PubChem = 
|   SMILES = Nc1ccc(N)cc1
|   InChI=1/C6H8N2/c7-5-1-2-6<br/>(8)4-3-5/h1-4H,7-8H2
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>6</sub>H<sub>8</sub>N<sub>2</sub>
|   MolarMass = 108.1
|   Appearance = white (tan when impure)
|   Density = 
|   MeltingPt = 143-145 °C
|   BoilingPtC = 267
|   Solubility = 
  }}
| Section3 = {{Chembox Hazards
|   MainHazards = 
|   FlashPt = 
|   Autoignition = 
|   RPhrases = {{R23}} {{R24}} {{R25}} {{R36}} {{R37}} {{R38}} {{R40}} {{R42}} {{R43}}
|   SPhrases = {{S26}} {{S36}} {{S37}} {{S39}}
  }}
}}

'''''p''-Phenylenediamine''' ('''PPD''') is an [[organic compound]] with the formula C<sub>6</sub>H<sub>4</sub>(NH<sub>2</sub>)<sub>2</sub>. This derivative of [[aniline]] is a colorless solid when pure, but typically samples are partially oxidized and appear yellowish. It is mainly used as a component of engineering [[polymer]]s and composites. It is an ingredient used in some [[Hair coloring|hair dyes]], though it may be a [[contact allergen]].

==Production==
PPD is produced via three routes.  Most commonly 4-nitrochlorobenzene is treated with ammonia and the resulting 4-aminonitrobenzene is then hydrogenated:
: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 DuPont route, aniline is converted to diphenyltriazine, which is converted by acid-catalysis to 4-aminoazobenzene.  Hydrogenation of the latter affords PPD.<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>

==Uses==
===Precursor to polymers===
PPD is a precursor to [[aramid]] plastics and fibers such as [[Kevlar]].  This polymer arises from the reaction of PPD and [[terephthaloyl chloride]].  The reaction of PPD with [[phosgene]] gives the di[[isocyanate]], a precursor to [[polyurethane|urethane]] polymers.<ref name=Ullmann/>

===Other uses===
PPD is easily oxidized, and for this reason PPD is used as [[antiozonant]]s in production of [[rubber]] products.  PPD is also used as a developing agent in the [[C-41 process|C-41]] color photographic film development process, reacting with the silver grains in the film and creating the colored dyes that form the image.

===Dyeing===
This compound is used in almost every [[hair dye]] on the market, regardless of brand. The darker the colour, usually, the higher the concentrations. Some of the so-called "natural" and "herbal" hair colours, while [[ammonia]]-free, contain PPD. Some products sold as [[henna]] also contain PPD added, particularly so-called "black henna." In many cases, PPD causes allergic reaction, and can cause scarring in some people. PPD should never be applied directly to the skin in its pure form or mixed with anything else.<ref>[http://www.hennapage.com/henna/ppd/smallbroch1.pdf "Henna is not black"], hennapage.com</ref>

== Safety ==
The aquatic LD50 of PPD is 0.028 mg/L.<ref name=Ullmann/>  The U.S. Environmental Protection Agency reported that in rats and mice chronically exposed to PPD in their diet, it simply depressed body weights, but there were no other clinical signs of toxicity, as were observed in several studies.<ref>[http://www.epa.gov/ttn/atw/hlthef/phenylen.html p-Phenylenediamine], U.S. Environmental Protection Agency</ref> Between 1992 and 2005, thirty-one articles were published a causal association between PPD and cancer. Associations between personal hair dye use and non-Hodgkin's lymphoma, multiple myeloma, acute leukemia, and bladder cancer<ref>{{cite journal | pmid = 17492526 | year = 2006 | last1 = Rollison | first1 = DE | last2 = Helzlsouer | first2 = KJ | last3 = Pinney | first3 = SM | title = Personal hair dye use and cancer: a systematic literature review and evaluation of exposure assessment in studies published since 1992. | volume = 9 | issue = 5 | pages = 413–39 | doi = 10.1080/10937400600681455 | journal = Journal of toxicology and environmental health. Part B, Critical reviews}}</ref> were observed in at least one well-designed study with detailed exposure assessment, but were not consistently observed across studies. However, the EPA has not classified PPD as a carcinogen. Therefore, no warnings of toxicity have been printed on boxes of hair dye.

The [[Center for Disease Control|CDC]] lists PPD as being a contact [[allergen]].  Exposure routes are through inhalation, skin absorption, ingestion, and skin and/or eye contact; symptoms of exposure include throat irritation ([[pharynx]] and [[larynx]]), bronchial [[asthma]], and sensitization [[dermatitis]].<ref>[http://www.cdc.gov/niosh/ipcsneng/neng0805.html The NIOSH Pocket Guide to Chemical Hazards]</ref><ref>[http://www.cdc.gov/niosh/rtecs/ss7ad550.html NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) entry for p-Phenylenediamine (PPD)]</ref> Sensitization is a lifelong issue, which may lead to active sensitization to products including, but not limited to black clothing, various inks, hair dye, dyed fur, dyed leather, and certain photographic products.

It was voted [[Allergen of the Year]] in 2006 by the American Contact Dermatitis Society.

==References==
{{reflist}}

==External links==
* [http://www2.dupont.com/Specialty_Chem_Intermediates/en_US/products/ppd.html Du Pont technical data sheet and sales policy for p-Phenylenediamine (PPD)]

{{DEFAULTSORT:Phenylenediamine, p-}}
[[Category:Aromatic amines]]
[[Category:Polyamines]]
[[Category:Monomers]]

[[de:Phenylendiamine]]
[[fr:Para-Phénylènediamine]]
[[it:1,4-fenilendiammina]]
[[nl:P-fenyleendiamine]]
[[pl:Diaminobenzeny]]
[[pt:P-fenilenodiamina]]
[[Category:2Fix]]