87-02-5

Gray needles, white when pure. Soluble in hot water; sparingly soluble in cold water.

ChEBI: An aminonaphthalenesulfonic acid that is 2-naphthalenesulfonic acid substituted by an amino group at position 7 and a hydroxy group at position 4 respectively.

A concentrated disodium salt solution of 2-aminonaphthalene-5,7-disulfonic acid is added to 72 % sodium hydroxide at 150 ℃. After heating to 187℃ over 10 h reaction is continued at this temperature for a further 8 h until completion of the reaction is indicated by giving equivalent diazotization and coupling titers for a worked-up sample. Quenching, acidification, purging of sulfur dioxide, and filtration at 55 ℃ followed by washing with water at 50℃ result in an 88 % yield of paste. Purification by salting out the sodium salt from a hot alkaline solution gives a 90 % recovery of the product as gray crystals. An improved process with 90 % yield is claimed by feeding the concentrated 2-aminonaphthalene-5,7-disulfonic acid liquor and the caustic liquor simultaneously into the fusion reactor to maintain more stable conditions.

Notclassified