With diazotized benzidine it gives Congo red.
Gattermann, Ber., 1893, 26, p. 1844); in alcoholic alkaline solution it yields azoxybenzene; in acid alcoholic solution, benzidine; in ammoniacal alcoholic solution, phenylhydrazine.
It is used commercially for the preparation of aniline and of benzidine; and in perfumery (oil of mirbane).
BENZIDINE (DIPARA-DIAMINO-DIPHENYL),NH 2 C 6 H 4 C 6 H 4 NH2, a chemical base which may be prepared by the reduction of the corresponding dinitro-diphenyl, or by the reduction of azobenzene with tin and hydrochloric acid.
In this latter case hydrazo-benzene C 6 H 5 NH NH C 6 H 5 is first formed and then undergoes a peculiar re-arrangement into benzidine (see H.
Benzidine crystallizes in plates (from water) which melt at '22' C., and boil above 360° C., and is characterized by the great insolubility of its sulphate.
Benzidine finds commercial application since its tetrazo compound couples readily with amino-sulphonic acids, phenol carboxylic acids, and phenol and naphthol-sulphonic acids to produce substantive cotton dyes (see Dyeing).
Among such dyestuffs are chrysamine or flavophenine, obtained from salicylic acid and diazotized benzidine, and congo red obtained from sodium naphthionate and diazotized benzidine.
On the constitution of benzidine see G.
The Benzidine and Semidine Change.-Aromatic hydrazo compounds which contain free para positions are readily converted by the action of acids, acid chlorides and anhydrides into diphenyl derivatives; thus, as mentioned above, hydrazobenzene is converted into benzidine, a small quantity of diphenylin being formed at the same time.
This reaction is known as the benzidine transformation.