Naphthionic acid is an organic compound with the formula . It is one of several aminonaphthalenesulfonic acids, which are derivatives of naphthalene containing both amine and sulfonic acid functional groups. Naphthionic acid is a white solid, although commercial samples can appear gray.4-Amino-1-naphthalenesulfonic acid; MSDS No. 250619; Sigma–Aldrich Chemie GmbH: Steinheim, 29 Dec 2011. Deprotonation of naphthionic acid gives the sulfonate , which is call naphthionate.
Production and reactions Naphthionic acid is prepared by treating 1-aminonaphthalene with sulfuric acid.Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. .
Naphthionic acid is used in the synthesis of azo dyes such as Rocceline (also known as Solid Red A). For this conversion sodium naphthionate is diazotated. The resulting diazonium derivative is coupled with β-naphthol.
Heating a solution of sodium naphtionate induces its conversion to 1-aminonaphthalene-2-sulfonate.
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