Question

Common name of azo compound formed by coupling of aniline and phenol

Answer 1

AZO COMPOUNDS, organic substances of the type RN:NR' (where R = an aryl radical and R' = a substituted alkyl, or aryl radical). They may be prepared by the reduction of nitro compounds in alkaline solution (using zinc dust and alkali, or a solution of an alkaline stannite as a reducing agent); by oxidation of hydrazo compounds; or by the coupling of a diazotized amine and any compound of a phenolic or aminic type, provided that there is a free para position in the amine or phenol. They may also be obtained by the molecular rearrangement of the diazoamines, when these are warmed with the parent base and its hydrochloride. This latter method of formation has been studied by H. Goldschmidt and R. U. Reinders (Ber.,1896, 29, p. 1369), who found that the reaction is monomolecular, and that the velocity constant of the reaction is proportional to the amount of the hydrochloride of the base present and also to the temperature, but is independent of the concentration of the diazoamine. The azo compounds are intensely coloured, but are not capable of being used as dyestuffs unless they contain salt-forming, acid or basic groups (see Dyeing). By oxidizing agents they are converted into azoxy compounds, and by reducing agents into hydrazo compounds or amines.

Azo-benzene, C 6 H 5 N:NC 6 H 5y discovered by E. Mitscherlich in 1834, may be prepared by reducing nitrobenzene in alcoholic solution with zinc dust and caustic soda; by the condensation of nitrosobenzene with aniline in hot glacial acetic acid solution; or by the oxidation of aniline with sodium hypobromite. It crystallizes from alcohol in orange red plates which melt at 68° C. and boil at 293° C. It does not react with acids or alkalis, but on reduction with zinc dust in acetic acid solution yields aniline.