Naphthalenesulfonic 8-hydroxy-6-

Disodium salt of 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl)a2o]-2-naphthalenesulfonic acid... 

Another example of manufacture in this series is the sulfonation of an aminonaphthalenesulfonic acid, followed by selected desulfonation, to make 6-amino-l,3-naphthalenedisulfonic acid (21). Thus, 2-amino-l-naphthalenesulfonic acid made by amination of 2-hydroxy-1-naphthalenesulfonic acid is added to 20 wt % oleum at ca 35°C. At this temperature, 65 wt % oleum is added and the charge is stirred for 2 h, is then slowly heated to 100°C and is maintained for 12 h to produce 6-amino-l,3,5-naphthalenetrisulfonic acid. The mass is diluted with water and maintained for 3 h at 105°C to remove the sulfo group adjacent to the amino group. After cooling to ca 20°C and filtration, 6-amino-l,3-naphthalenedisulfonic acid is obtained in 80% yield (55). 

Naphthalenediol. This compound darkens rapidly in air. It can be made by fusion of the sultone of 8-hydroxy-1-naphthaIenesulfonic acid with 50 wt % sodium hydroxide at 200—230°C, or by the hydrolytic desulfonation of l,8-dihydroxy-4-naphthalenesulfonic acid. The diol also reacts with ammonia to give 1,8-naphthalenediamine. 

The manufacture of 4-hydroxy-6-amino-2-naphthalenesulfonic acid in ca 85% of the theoretical yield has been described (76). 

Manufacture of 3-hydroxy-4-amino-l-naphthalenesulfonic acid involves the nitrosation of 2-naphthalenol, bisulfite addition, and reduction of the nitroso to the amino group by sulfur dioxide generated in situ (47). 3-Hydroxy-4-amino-l-naphthalenesulfonic acid is obtained in 80% yield. 

By the nitrosation of 2-naphthalenol and the reaction of the nitroso compound with sodium bisulfite. By nitrosation/reduction of 6-hydroxy-2-naphthalenesulfonic acid. 

In mordant dyes, phenols, naphthols, and enolizable carbonyl compounds, such as pyrazolones, are generally the couplers. As a rule, 2 1 metal complexes are formed ia the afterchroming process. A typical example of a mordant dye is Eriochrome Black T (18b) which is made from the important dyestuff iatermediate nitro-l,2,4-acid, 4-amiQO-3-hydroxy-7-nitro-l-naphthalenesulfonic acid [6259-63-8]. Eriochrome Red B [3618-63-1] (49) (Cl Mordant Red 7 Cl 18760) (1, 2,4-acid — l-phenyl-3-methyl-5-pyrazolone) is another example. The equiUbrium of the two tautomeric forms depends on the nature of the solvent. 

FD C Red No. 40. This monoa2o dye (5) is manufactured by coupling dia2oti2ed 5-amino-4-methoxy-2-toluenesulfonic with 6-hydroxy-2-naphtha-lenesulfonic acid. FD C Red No. 40 is also known as Allura Red or Cl Food Red 17. Its chemical identity is principally the disodium salt of 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl)a2o]-2-naphthalenesulfonic acid, which has the formula C gH 4N20gS2Na2, and mol wt 496.43. 

Interesting regioselectivities have been known for more than 100 years for azo coupling reactions with aminonaphthol derivatives such as 6-amino-4-hydroxy-2-naphthalenesulfonic acid (12.136, y-acid), 7-amino-4-hydroxy-2-naphthalenesulf-onic acid (J-acid), and 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid (H-acid). They give two types of isomeric azo compounds depending on the pH-value of the... 

Naphthoresorcinol has been prepared by heating l-amino-3-hydroxy-4-naphthalenesulfonic acid or its salt in water or slightly acidic solution2 and by cyclization of ethyl phenylacetylmalo-nate 3 or of ethyl phenylacetoacetate.4 Phenylacetylmalonic ester has been prepared by condensing phenylacetyl chloride and malonic ester in ether with sodium.3... 

Yamada et al. (201) developed a method for the determination of starting materials (7-hydroxy-1,3,6-naphthalenesulfonic acid, G-salt, R-salt, Schaeffer s salt, and naphthionic salt) and subsidiary colors (Ponceau 6R, amaranth, and fast red) in Ponceau 4R. It consisted of an ODS column and gradient elution of acetonitrile in 0.02 M ammonium acetate. 

A strong anion-exchange column and a gradient of 0-100% of B (10 mM aqueous Na2B407 in 0.5 M NaC104.H20) in A (10 mM Na2B407) was used by Marmion (208,209) for the separation of sunset yellow from 4,4 -(diazoamino)-dibenzenesulfonic acid (DAADBSA). This same system was used by Singh (210) for the separation of sunset yellow from the intermediates sulfanilic acid, 6-hydroxy-2-naphthalenesulfonic acid, and DONS. Useful information on the identification and confirmation of products related to sunset yellow are described by Bailey and Calvey (211). 

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