Benzeneazo-a-naphthol

The only practical method of preparing 1,4-aminonaphthol is from a-naphthol through an azo dye, the nitroso compound not being readily available. The majority of investigators have reduced technical Orange I with stannous chloride Mi.is.is.ir.is by the procedures discussed above, and benzeneazo-a-naphthol has been reduced by the same reagent. In order to make possible the use of crude, technical a-naphthol a method has been developed for the preparation of the benzeneazo compound, its separation from the isomeric dye coming from the d-naphthol present as well as from any disazo compound by extraction with alkali, and the reduction of the azo compound in alkaline solution with sodium hydrosulfite. The process, however, is tedious and yields an impure product. 

The moist benzeneazo-a-naphthol is next transferred to a 5-1. wide-mouth bottle or a 2-gal. crock equipped with a mechanical stirrer and containing 3 1. of 10 per cent sodium hydroxide solution. The mixture is stirred for ten minutes to insure solution of the dye, and then filtered. The insoluble solid is stirred up with 500 cc. of xo per cent sodium hydroxide, filtered again and washed with water. The solid, which weighs 10-90 g, consists mainly of the 2,4-disazo derivative (m. p. 197-198°), together with any benzeneazo-/3-naphthol that may be present. 

Azobenzene. o-Azotoluene. m-Azotoluene p-Azotoluene o-Azophenetole p-Azophenetole Benzeneazo-o-cresol a-Benzeneazo- P-naphthol P-Benzeneazo-a-naphthol 4-Benzeneazo- a-naphthol Benzeneazodiphenylamine a-Benzeneazo- P-naphthylamme 4-Benzeneazo- a-naphthylamme p-Aminoazobenzene p-Dimethylaminoazobenzene. p-Hydroxyazobenzene. ... 

Since, in the case of the benzeneazo-a-naphthol, both forms are present in appreciable quantities at equilibrium, it is possible to observe the effects of substituents on the position of the equilibrium. This has been done for a number of substitutions in the benzene part of the molecule of such groups as CHa, CH3O, NO2, halogen, CO2H,... 

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