4-amino-1-naphthol

Acicular crystals. Soluble in water.

Inhibitor of polymerization, chemical intermediate. Must be kept dry during storage to avoid oxidation and discoloration.

Orange I in aqueous alkaline solution is treated with sodium dithionite at 40 – 50℃, and the resulting suspension is heated to 70℃ to complete the reaction. The crude product is collected by filtration and dissolved in hot aqueous hydrochloric acid in the presence of a reducing agent. On cooling, needles of the hydrochloride salt crystallize and can be isolated in 70 % yield. Alternatively, the crude paste may be dissolved in dilute alkali in the presence of a reducing agent and acylated with acetic anhydride or acryloyl chloride, for example, to give 4- acetylamino-1-naphthol or 4-acryloylamino-1- naphthol, which have been used as azo coupling components.