Phenylenediamines

Phenylenediamines

 

(also diaminobenzenes), C6H4(NH2)2, aromatic diamines. Ortho, meta, and para isomers are known, occurring as colorless crystals that darken upon exposure to light and air. Their melting points are 102°, 63°–64°, and 147°C, respectively. Phenylenediamines are soluble in hot water, alcohol, and diethyl ether; they form salts with mineral acids and are readily oxidized and acylated. The meta and para isomers undergo diazotization, a property that forms the basis of their use in the synthesis of dyes (azine, oxazine, thiazine). Polyamides, for example, Phenylone, which are obtained through the condensation of meta-phenylenediamine with isophthalic acid, are important in industry.

Phenylenediamines are used in analytical chemistry. Ortho-phenylenediamine is a reagent for diketones, carboxylic acids, and aldehydes, and meta-phenylenediamine is a reagent for the nitrite ion. The sulfate of N, N-diethyl-para-phenylenediamine is used as a developer in color photography. Phenylenediamines are produced synthetically. Ortho-phenylenediamine is obtained through the reduction of ortho-nitroaniline and through the action of an aqueous ammonia solution on ortho-chloroaniline and ortho-dichlorobenzene; meta-phenylenediamine is obtained through the reduction of meta-dinitrobenzene; and para-phenylenediamine is produced by the reduction of para-nitro-aniline and by the action of aqueous ammonia on para-dichloro-benzene in the presence of CuSO4.

References in periodicals archive ?
One, referred to as the "primary," is exemplified by the phenylenediamines, and the other, often an aminophenol, is known as the "coupler.
Chemicals called phenylenediamines (PDD) are added to some dyes to enable absorption of the colour.
Phenylenediamines seem to impede the reduction of viscosity of the powder rubber.
Some of the alkylated diphenylamines are less discoloring than the phenylenediamines and find application in plastics.
Perhaps the three most commonly used antiozonants are N-isopropyl-N'-phenyl-p-phenylenediamine (1PPD), N-1,3-dimethylbutylN'-phenyl-p-phenylene diamine (6PPD) and N,N'-bis(1,4-dimethylpentyl)-p phenylenediamine (77PD).