Aminonaphthalenesulfonic acids

Aminonaphthalenesulfonic acids are compounds with the composition C₁₀H₆(NH₂)(SO₃H), being derived from naphthalene (C₁₀H₈) substituted by an amino and sulfonic acid groups. These compounds are colorless solids. They are useful precursors to dyes.^[1]

1-Aminonaphthalenesulfonic acids

Isomer	CAS Registry Number	Alternative names	Preparative route, notes
1-Aminonaphthalene-4-sulfonic acid	84-86-6	Piria’s acid, naphthionic acid	sulfonation of 1-aminonaphthalene, precursor to acid red 25, C.I. food red 3, C.I. food red 7, C.I. food red 9, and C.I.
1-Aminonaphthalene-5-sulfonic acid	84-89-9	Laurent’s acid, L acid, Purpurin acid	reduction of 1-nitronaphthalene-5-sulfonic acid. With NaOH, converts to 5-amino-1-naphthol ("purpurol").
1-Aminonaphthalene-6-sulfonic acid	119-79-9	1,6-Cleve’s acid (named after swedish chemist Per Teodor Cleve)	sulfonation of 1-aminonaphthalene
1-Aminonaphthalene-7-sulfonic acid	119-28-8	1,7-Cleve’s acid	by-product in production of 1,6-Cleve’s acid, precursor to C.I. Acid Black 36
1-Aminonaphthalene-8-sulfonic acid	82-75-7	Peri acid	reduction of 1-nitroonaphthalene-8-sulfonic acid, precursor to C.I. Acid Blue 113

Notes: Peri-acid dehydrates to the sultam. Via the Bucherer reaction, heating periacid with anilinium salts gives the N-phenyl derivative, precursor to Acid Blue 113.

2-Aminonaphthalenesulfonic acids

Isomer	CAS Registry Number	Alternative names	Preparative route and notes
2-Aminonaphthalene-1-sulfonic acid	81-16-3	Tobias acid	Bucherer reaction of 2-hydroxynaphthalene-1-sulfonic acid with ammonium salts, precursor to C.I. Pigment Red 49
2-Aminonaphthalene-5-sulfonic acid	81-05-0	Dahl’s acid, Dressel acid, D acid	Desulfonation of 2-aminonaphthalene-1,5-disulfonic acid
2-Aminonaphthalene-6-sulfonic acid	93-00-5	Bronner acid	Bucherer amination of 2-hydroxynaphthalene-6-sulfonic acid
2-Aminonaphthalene-7-sulfonic acid	494-44-0	Amido F acid; Delta acid; Monosulphonic F acid	Bucherer amination of 2-hydroxynaphthalene-7-sulfonic acid
2-Aminonaphthalene-8-sulfonic acid	86-60-2	Badische acid	Bucherer amination of 2-hydroxynaphthalene-8-sulfonic acid