R. Layer
Dec 4, 2000
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Abstract
Phenylenediamines are aromatic amines with two amino groups attached to benzene. They are called benzenediamines by Chemical Abstracts. There are three phenylenediamines; ortho, meta, and para; or 1,2-; 1,3-; and 1,4-benzenediamines, respectively. Since they are difunctional, they are easily converted to polymers. The m-phenylenediamines are the least expensive isomers and are used in the largest volumes for the manufacture of polyurethanes. p-Phenylenediamine is used for the manufacture of polyamides with exceptional tensile strength. The unique chemistry of the p-phenylenediamine derivatives makes them useful in the photographic and dye industries, and widely used as antioxidants and antiozonants for rubbers and plastics. The three phenylenediamines are all white solids when pure, but darken after standing in air. They are all very soluble in hot water. The phenylenediamines are aromatic amines which undergo typical amine reactions, such as N-acylation and N-alkylation. Commercially the largest-volume usage of phenylenediamines is in the manufacture of diisocyanates; large volumes of N,N′-alkyl/aryl-p-phenylenediamines are also manufactured. The m-phenylenediamines are easily obtained by dinitrating, followed by catalytically hydrogenating, an aromatic hydrocarbon. Like aniline, phenylenediamines may be toxic. Appropriate substitution of p-phenylenediamine, generally on the nitrogen with phenyl or larger alkyl groups, significantly reduces its toxicity. Keywords: Phenylenediamines; Benzendiamines; Polyurethanes; Dyes; Photography; Liquid crystalline materials; Heat resistant