2-Naphthylamine or 2-aminonaphthalene is one of two isomeric aminonaphthalenes, compounds with the formula C₁₀H₇NH₂. It is a colorless solid, but samples take on a reddish color in air because of oxidation. It was formerly used to make azo dyes, but it is a known carcinogen and has largely been replaced by less toxic compounds.^[2]

2-Naphthylamine is prepared by heating 2-naphthol with ammonium zinc chloride to 200-210 °C, the Bucherer reaction. Its acetyl derivative can be obtained by heating 2-naphthol with ammonium acetate to 270-280 °C.

It gives no color with iron(III) chloride. When reduced by sodium in boiling amyl alcohol solution, it forms tetrahydro-3-naphthylamine, which exhibits the properties of the aliphatic amines in that it is strongly alkaline in reaction, has an ammoniacal odor and cannot be diazotized.

On oxidation, it yields ortho-carboxy-hydrocinnamic acid, HO₂CC₆H₄CH₂CH₂CO₂H.

Numerous sulfonic acid derivatives of 2-naphthylamine are used in commerce, such as precursors to dyes.^[2] Owing to the carcinogenicity of the amine, these derivatives are mainly prepared by amination of the corresponding naphthols. Of them, the δ-acid and Bronner's acid are of more value technically, since they combine with ortho-tetrazoditolyl to produce fine red dye-stuffs.

2-Naphthylamine was previously used as a dye precursor and rubber antioxidant in the 1930s, 40s and 50s. Dupont stopped using it in the 1970s.^[3]

2-Naphthylamine is found in cigarette smoke and suspected to contribute to the development of bladder cancer.^[4]

It is activated in the liver but quickly deactivated by conjugation to glucuronic acid. In the bladder, glucuronidase re-activates it by deconjugation, which leads to the development of bladder cancer.

• Naphthalene
• Naphthol
• 1-Naphthylamine
• 1,8-Bis(dimethylamino)naphthalene