NOVEL PREPARATION OF 1,8-DINITRONAPHTHALENE-3,6-DISULFONIC ACID, AND PREPARATION OF HIGH-PURITY 1-AMINO-8- HYDROXYNAPHTHALENE-3,6-DISULFONIC ACID USING ITS METHOD

PURPOSE:To obtain the titled compound useful as an intermediate for dye in high yield, by dinitrating 2,7-naphthalenedisulfonic acid under specific conditions to give a high-purity compound, reducing and hydrolyzing it under specified conditions. CONSTITUTION:In nitrating 2,7-naphthalenedisulfonic acid with a mixed acid in a solvent of sulfuric acid, a reaction from a mononitro derivative to a dinitro derivative is carried out in conditions of reaction system wherein the dehydration value is 5-27, the reaction temperature is -20-40 deg.C, 6-15mol sulfuric acid is used based on 1mol naphthalene skeleton. After dropping of a nitrating agent is over, and no mononitro derivative is detected, the dinitro derivative is added to water, it is aged in a state of 80wt% sulfuric acid concentration for >=0.5hr under heating (preferable 50 deg.C- the boiling point) to finish dinitration. 1,8-Dinitronaphthalene-3,6-disulfonic acid obtained by the dinitration is reduced with iron powder, and hydrolyzed to give 1-amino-8-hydroxynaphthalene-3,6- disulfonic acid.