P-Phenylenediamine
Encyclopedia
p-Phenylenediamine is an organic compound
with the formula C6H4(NH2)2. This derivative of aniline
is a colorless solid, but typically samples can contain yellowish impurities arising from oxidation. It is mainly used as a component of engineering polymer
s and composites. It is also an ingredient in hair dyes
.
is treated with ammonia
and the resulting 4-nitroaniline
is then hydrogenated:
In the DuPont route, aniline is converted to diphenyltriazine, which is converted by acid-catalysis to 4-aminoazobenzene. Hydrogenation of the latter affords PPD.
plastics and fibers such as Kevlar
. These applications exploit PPD's difunctionality, i.e. the presence of two amines which allow the molecules to be strung together. 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.
. Other popular derivatives include tetraaminopyrimidine and indoanilines and indophenol
s. Derivatives of diaminopyrazole give red and violet colours. In these applications, the nearly colourless dye precursor oxidizes to the dye.
s in production of rubber
products. The substituents, naphthyl, isopropyl etc affect the effectiveness of their antioxidant roles as well as their properties as skin irritants.
color photographic film development process, reacting with the silver grains in the film and creating the colored dyes that form the image.
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
. 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.
Poisoning by PPD "is rare in western countries."
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the formula C6H4(NH2)2. This derivative of aniline
Aniline
Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...
is a colorless solid, but typically samples can contain yellowish impurities arising from oxidation. It is mainly used as a component of engineering polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s and composites. It is also an ingredient in hair dyes
Hair coloring
Hair coloring is the practice of changing the color of hair. Common reasons are to cover gray hair, to change to a color regarded as more fashionable or desirable, and to restore the original hair color after it has been discolored by hairdressing processes or sun bleaching...
.
Production
PPD is produced via three routes. Most commonly, 4-nitrochlorobenzene4-Nitrochlorobenzene
4-Nitrochlorobenzene is the organic compound with the formula ClC6H4NO2. This compound is a light yellow crystalline solid that is stable to air...
is treated with ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and the resulting 4-nitroaniline
4-Nitroaniline
4-Nitroaniline, p-nitroaniline or 1-amino-4-nitrobenzene is an organic compound with the formula C6H6N2O2. It is an organic chemical compound, consisting of a phenyl group attached to an amino group which is para to a nitro group. The chemical structure of p-nitroaniline is shown at the right...
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.
Precursor to polymers
PPD is a precursor to aramidAramid
Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide"...
plastics and fibers such as Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
. These applications exploit PPD's difunctionality, i.e. the presence of two amines which allow the molecules to be strung together. This polymer arises from the reaction of PPD and terephthaloyl chloride
Terephthaloyl chloride
Terephthaloyl chloride is the acid chloride of terephthalic acid and is one of two monomers used to make Kevlar, the other being p-phenylenediamine...
. The reaction of PPD with phosgene
Phosgene
Phosgene is the chemical compound with the formula COCl2. This colorless gas gained infamy as a chemical weapon during World War I. It is also a valued industrial reagent and building block in synthesis of pharmaceuticals and other organic compounds. In low concentrations, its odor resembles...
gives the diisocyanate
Isocyanate
Isocyanate is the functional group of elements –N=C=O , not to be confused with the cyanate functional group which is arranged as –O–C≡N or with isocyanide, R-N≡C. Any organic compound which contains an isocyanate group may also be referred to in brief as an isocyanate. An isocyanate may have more...
, a precursor to urethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
polymers.
Dyeing
This compound is a common hair dye. Its use is being supplanted by other aniline analogues and derivatives such as 2,5-diamino(hydroxyethylbenzene and 2,5-diaminotoluene2,5-Diaminotoluene
2,5-Diaminotoluene is an organic compound with the formula C6H32CH3. It is one isomer of six with this formula. 2,5-Diaminotoluene is a colorless crystalline solid that is commonly used in hair coloring.- Formation and use:...
. Other popular derivatives include tetraaminopyrimidine and indoanilines and indophenol
Indophenol
Indophenol is an artificial blue metachromatic dye, obtained by the action of phenol on certain nitrogenous derivatives of quinone. Indophenol resembles the color indigo in appearance...
s. Derivatives of diaminopyrazole give red and violet colours. In these applications, the nearly colourless dye precursor oxidizes to the dye.
Rubber antioxidant
PPD is easily oxidized, and for this reason derivatives of PPD are used as antiozonantAntiozonant
An antiozonant, also known as anti-ozonant, is a chemical compound that prevents or slows down the degradation of material caused by ozone gas in the air...
s in production of rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
products. The substituents, naphthyl, isopropyl etc affect the effectiveness of their antioxidant roles as well as their properties as skin irritants.
Other uses
PPD is also used as a developing agent in the C-41C-41 process
C-41 is a chromogenic color print film developing process. C-41, also known as CN-16 by Fuji, CNK-4 by Konica, and AP-70 by AGFA, is the most popular film process in use, with most photofinishing labs devoting at least one machine to this development process....
color photographic film development process, reacting with the silver grains in the film and creating the colored dyes that form the image.
Safety
The aquatic of PPD is 0.028 mg/L. The U.S. Environmental Protection Agency reported that in rats and mice chronically exposed to PPD in their diet, it simply depressed body weights, and no other clinical signs of toxicity were observed in several studies. One review of 31 English-language articles published between January 1992 and February 2005 that investigated the association between personal hair dye use and cancer as identified through the PubMed search engine found "at least one well-designed study with detailed exposure assessment" that observed associations between personal hair dye use and non-Hodgkin's lymphoma, multiple myeloma, acute leukemia, and bladder cancer, but those associations were not consistently observed across studies. A formal meta-analysis was not possible due to the heterogeneity of the exposure assessment across the studies.The CDC lists PPD as being a contact allergen
Allergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
. Exposure routes are through inhalation, skin absorption, ingestion, and skin and/or eye contact; symptoms of exposure include throat irritation (pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
and larynx
Larynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...
), bronchial asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
, and sensitization dermatitis
Dermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...
. 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
Allergen of the Year
Allergen of the Year is an annual 'award' of dubious distinction voted upon by the American Contact Dermatitis Society. It is "designed to draw attention to allergens that are very common and/or under-recognized and merit more attention because they are causing significant allergic contact...
in 2006 by the American Contact Dermatitis Society.
Poisoning by PPD "is rare in western countries."