p-Phenylenediamine
| p-Phenylenediamine | |
|---|---|
| File:P-phenylenediamine.png | |
| 1,4-diaminobenzene | |
| Other names paraphenylenediamine, 1,4-diaminobenzene, 1,4-phenylenediamine | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers | |
| CAS number | 106-50-3 
|
| SMILES | Script error: No such module "collapsible list". |
| InChI | Script error: No such module "collapsible list". |
| style="background: #F8EABA; text-align: center;" colspan="2" | Properties | |
| Molecular formula | C6H8N2 |
| Molar mass | 108.1 |
| Appearance | white (tan when impure) |
| Melting point |
143-145 °C |
| Boiling point |
267 °C, 540 K, 513 °F |
| style="background: #F8EABA; text-align: center;" colspan="2" | Hazards | |
| R-phrases | R23 R24 R25 R36 R37 R38 R40 R42 R43 |
| S-phrases | S26 S36 S37 S39 |
 (what is this?) (verify)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
p-Phenylenediamine (PPD) is an organic compound with the formula C6H4(NH2)2. 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 polymers and composites. It is an ingredient used in some hair dyes, though it may be a contact allergen.
Contents
Production
PPD is produced via three routes. Most commonly 4-nitrochlorobenzene is treated with ammonia and the resulting 4-aminonitrobenzene is then hydrogenated:
- ClC6H4NO2 + 2 NH3 → H2NC6H4NO2 + NH4Cl
- H2NC6H4NO2 + 3 H2 → H2NC6H4NH2 + 2 H2O
In the DuPont route, aniline is converted to diphenyltriazine, which is converted by acid-catalysis to 4-aminoazobenzene. Hydrogenation of the latter affords PPD.[1]
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 diisocyanate, a precursor to urethane polymers.[1]
Other uses
PPD is easily oxidized, and for this reason PPD is used as antiozonants in production of rubber products. PPD is also used as a developing agent in the 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.[2]
Safety
The aquatic LD50 of PPD is 0.028 mg/L.[1] 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.[3] 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[4] 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 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.[5][6] 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
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fr:Para-Phénylènediamine it:1,4-fenilendiammina nl:P-fenyleendiamine pl:Diaminobenzeny
pt:P-fenilenodiamina- ↑ 1.0 1.1 1.2 Robert A. Smiley “Phenylene- and Toluenediamines” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_405
- ↑ "Henna is not black", hennapage.com
- ↑ p-Phenylenediamine, U.S. Environmental Protection Agency
- ↑ Rollison, DE; Helzlsouer, KJ; Pinney, SM (2006). "Personal hair dye use and cancer: a systematic literature review and evaluation of exposure assessment in studies published since 1992". Journal of toxicology and environmental health. Part B, Critical reviews. 9 (5): 413–39. doi:10.1080/10937400600681455. PMID 17492526.
- ↑ The NIOSH Pocket Guide to Chemical Hazards
- ↑ NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) entry for p-Phenylenediamine (PPD)
