The molecule is a naphthalenesulfonic acid that is naphthalene-1-sulfonic acid carrying additional hydroxy and (2-methoxyphenyl)diazenyl substituents at positions 4 and 3 respectively. The sodium salt is the biological stain 'acid red 4'. It is a naphthalenesulfonic acid, a member of azobenzenes, a member of naphthols and an aromatic ether. It is a conjugate acid of a 4-hydroxy-3-[(2-methoxyphenyl)diazenyl]naphthalene-1-sulfonate.
4-hydroxy-3-[(2-methoxyphenyl)diazenyl]naphthalene-1-sulfonic acid