Diphenylamine dyestuff intermediate

Diphenylamine [ISV] (1872) (DPA) n. (C6H5)2NH. a crystalline solid. Used as a stabilizer for several plastics. Also, a weak secondary base used as a dyestuff intermediate and as an indicator. 

Uses Diphenylamine is a colorless, monoclinic leaflet substance. It is used in the manufacture of a variety of substances, (e.g., dyestuffs and their intermediates pesticides, antihelmintic drugs, as a reagents in analytical chemistry laboratories). 

After diazotisation is completed the liquid is allowed to run into an alkaline solution of the phenol or its sulphonic acid, care being taken that the mixture remains alkaline. After some time the dyestuff is salted out, and is generally filtered through a filter-press. The combination of diazo-compounds with amines is somewhat more complicated. Some of these, for instance metaphenylenediamine, combine with diazo-compounds in neutral aqueous solutions while others, like diphenylamine, are dissolved in alcohol, and a concentrated solution of the diazo-compound gradually added. In the manufacture of amidoazobenzene and all compounds in which an intermediate formation of a diazo-amido-compound takes place, a large excess of the amine has to be employed, to hold the diazoamido-compound formed in solution. 

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