Diphenylamine
Encyclopedia
Diphenylamine is the organic compound
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
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 (C6H5)2NH. It is a colourless solid, but samples are often yellow due to oxidized impurities.

Preparation and reactivity

Diphenylamine is manufactured by the thermal deamination 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...

 over oxide catalysts:
2 C6H5NH2 → (C6H5)2NH + NH3

It is a weak base, with a Kb of 10−14. With strong acids, it forms the water soluble salt.

Applications

Diphenylamine is used as a pre- or postharvest scald inhibitor for apples. Its anti-scald activity is the result of its antioxidant properties, which protect the apple skin from the oxidation products of alpha-farnesene during storage.

Diphenylamine derivatives are also useful. Ring-alkylated derivatives of diphenylamine are used as "antiozinates" in the manufacture of rubber products, reflecting the antioxidant nature of aniline derivatives. The compound undergoes various cyclisaton reactions. With sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

, it gives phenothiazine
Phenothiazine
Phenothiazine is an organic compound that occurs in various antipsychotic and antihistaminic drugs. It has the formula S2NH. This yellow tricyclic compound is soluble in acetic acid, benzene, and ether. The compound is related to the thiazine-class of heterocyclic compounds...

, a precursor to certain pharmaceuticals.
(C6H5)2NH + 2 S → S(C6H4)2NH + H2S

With iodine, it cyclises to carbazole
Carbazole
Carbazole is an aromatic heterocyclic organic compound. It has a tricyclic structure, consisting of two six-membered benzene ring fused on either side of a five-membered nitrogen-containing ring...

:
(C6H5)2NH + I2 → (C6H4)2NH + 2 HI
Hydrogen iodide
Hydrogen iodide is a diatomic molecule. Aqueous solutions of HI are known as iohydroic acid or hydroiodic acid, a strong acid. Gas and aqueous solution are interconvertible...


Arylation with iodobenzene
Iodobenzene
Iodobenzene is an organic compound consisting of a benzene ring substitituted with one iodine atom. It is useful as a synthetic intermediate in organic chemistry.-Preparation:...

 gives triphenylamine
Triphenylamine
Triphenylamine is an organic compound with formula 3N. In contrast to most amines, triphenylamine is nonbasic. Its derivatives have useful properties in electrical conductivity and electroluminescence, and they are used in OLEDs as hole-transporters....

.

Diphenylamine finds niche use as a test for nitrates (see nitrate test
Nitrate test
A nitrate test is a chemical test used to determine the presence of nitrate ion in solution. Testing for the presence of nitrate via wet chemistry is generally difficult compared with testing for other anions, as almost all nitrates are soluble in water. In contrast, many common ions give insoluble...

).
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