P-Phenylenediamine(p-Phenylenediamine),also known as Urs D,is one of the simplest aromatic diamines and a widely used intermediate.It can be used to prepare azo dyes and high molecular polymers.It can also be used to produce fur stains,rubber antioxidants and photo developers.In addition,p-phenylenediamine is also a commonly used sensitive reagent for testing iron and copper.P-phenylenediamine is an extremely important dye intermediate,mainly used in aramid,azo dyes,sulfur dyes,acid dyes,etc.

　　Physical properties

　　Main physical properties of p-phenylenediamine:p-phenylenediamine is white to light purple-red flaky crystals,flammable.Melting point 138-147℃,boiling point 267℃,flash point 155.6℃.Slightly soluble in cold water,soluble in hot water,ethanol,ether,chloroform and benzene.When exposed to air,it becomes purple or dark brown.Can sublimate.This product is toxic and is basically the same as o-phenylenediamine.

　　Chemical properties

　　P-phenylenediamine chemical properties:p-phenylenediamine molecule has benzene ring and amino group,so it has the properties of these two functional groups.

　　⑴Flammability:

　　⑵Weak alkaline:Because there are amino groups,it has weak alkaline.

　　(3)Reducibility:The amino group has reducibility and is easily oxidized by strong oxidants.

　　⑷Substitution reaction:The benzene ring is influenced by the amino group to enhance the activity of hydrogen in the ortho-para position of the amino group on the benzene ring,and it is easy to be substituted.

　　⑸Addition reaction:

　　Reactions involving amino groups

　　The reaction of phenylenediamine mainly takes place on the amino group,and a series of derivatives can be obtained.The related reactions include N-alkylation and N-arylation,condensation,diazotization,oxidation,etc.

　　⑴Reaction with acid:as a weak base,p-phenylenediamine reacts with inorganic acid to form a salt soluble in water.Under normal diazotization conditions,treatment with nitrous acid produces a mixture of diazo compounds and double nitrogen compounds;treatment with phosphoric acid/sulfuric acid mixture with nitroxyl sulfate produces double nitrogen compounds.

　　⑵Oxidation reaction:p-phenylenediamine is easily oxidized and quickly oxidizes to a deep color in the air.In the presence of sulfuric acid,p-phenylenediamine is oxidized to p-benzoquinone with manganese dioxide or sodium dichromate.When oxidized in the presence of aniline or o-toluidine,a blue indamide is formed,which turns into a basic saffron upon boiling.Slow oxidation with potassium ferricyanide in ammonia produces p-benzoquinone diimine.This compound is unstable and can further react to form a complex compound-Bandrovsky base,which is generated when dyeing hair and fur An intermediate.P-Phenylenediamine is oxidized to an azomethine dye in the presence of active methylene compounds.

　　Reactions involving benzene ring

　　C-alkylation,sulfonation,chlorination,nitration and other reactions can occur on the benzene ring of p-phenylenediamine,but there are few reports.