1-Naphthylamine

1-Naphthylamine is an aromatic amine derived from naphthalene. It can cause bladder cancer (transitional cell carcinoma). It crystallizes in colorless needles which melt at 50 °C. It possesses a disagreeable odor, sublimes readily, and turns brown on exposure to air. It is the precursor to a variety of dyes.

Preparation and reactions
It can be prepared by reducing 1-nitronaphthalene with iron and hydrochloric acid followed by steam distillation.

Oxidizing agents, such as ferric chloride, give a blue precipitate with solutions of its salts. Chromic acid converts it into 1-naphthoquinone. Sodium in boiling amyl alcohol reduces the unsubstituted ring, giving tetrahydro-1-naphthylamine. This tetrahydro compound yields adipic acid when oxidized by potassium permanganate.

At 200 °C in sulfuric acid, it converts to 1-naphthol.

Use in dyes
The sulfonic acid derivatives of 1-naphthylamine are used for the preparation of azo dye. These compounds possess the important property of dyeing unmordanted cotton.

An important derivative is naphthionic acid (1-aminonaphthalene-4-sulfonic acid), which is produced by heating 1-naphthylamine and sulfuric acid to 170–180 °C in the presence of crystallized oxalic acid. It forms small needles, very sparingly soluble in water. Upon treatment with the bis(diazonium) derivative of benzidine, 1-aminonaphthalene-4-sulfonic acid gives Congo red.

Safety
It is listed as one of the 13 carcinogens covered by the OSHA General Industry Standards.