2.3- Dihydroxynaphthalene-6-sulfonic

Replacement of the sulfo group by hydrogen instead of by hydroxyl, simultaneously forming sulfate instead of sulfite. This reaction is usually only an unimportant side reaction, but in certain cases it may become the main reaction. Thus, alkali fusion of 2,3-dihydroxynaphthalene-6-sulfonic acid does not give the expected 2,3,6-trihydroxynaphthalene, but instead, 2,3-dihydroxynaphthalene. 

In a recent paper Cox et al. found, as expected, that the triple anion of 2,3-dihydroxynaphthalene-6-sulfonic acid has a higher reactivity than the double anion. They observed a specific catalytic effect of borate buffers, but unfortunately they did not investigate it further. 

Despite this, many of the compounds tested are only weakly active while others show relative activities not predicted by their stability constants. Of the compounds shown in Figure 1, 3-isopropyl-tropolone, 1,8-dihydroxynaphthalene and acetohydroxamlc acid are essentially inactive, while 2,3-dihydroxynaphthalene-6-sulfonic acid and 8-hydroxyqulnoline are active in both screens. EHPG (B = 1Q33-9, Keff = 10 ) is more effective than HBED (B = 10 , ... 

Dihydroxynaphthalene [83-56-7] behaves similarly to 1-naphthol coupling takes place mainly in the 4-position by simple diazonium compounds, and in the 2-position with diazophenols. Diazotized 2-arninophenol-4-sulfonic acid [98-37-3] couples with 1,5-dihydroxynaphthalene to produce the important mordant dye Diamond Black PV [2052-25-7] (see stmcture 53) (Cl Mordant Black 9 Cl 16500). 

Al-Ghannam et al. [25] described a simple fluorimetric procedure for determination of three pharmaceutical compounds containing thiol groups, including penicillamine. In this method, the drugs are treated with 1,2-naphthoquinone-4-sulfonic acid. The later compound is reduced to l,2-dihydroxynaphthalene-4-sulfonic acid, which is measured fluorimetrically (excitation = 318 nm, emission = 480 nm). The method is sensitive to 0.5 1.5 pg/mL, with a detection limit of 0.05 pg/mL (S/N = 2). 

The core scaffold of three of the previously identified inhibitors, VI, SI, and S5 (31), is 4,5-dihydroxynaphthalene-2,7-disulfonate—structure A in Durrant et al. (47). Similarity searches were performed using three structures similar to this core scaffold naphthalene-2-sulfonic acid, 2-naphthoic acid, and 2-nitronaphthalene—structures B, C, and D in Fig. 1 of Durrant et al. (47), respectively. 

G acid is subjected to fusion with NaOH and a small amount of water at 200° in an open vessel to yield 2,8-dihydroxynaphthalene-6-sulfonic acid. This product... 

Dihydroxynaphthalenemono- and disulfonic acids couple so rapidly, even the second time, that the coupling is carried out in acetic acid solution containing sodium acetate, using diazotized p-aminoacetanilide. With many of the acids, the coupling requires several hours, as, for example, with chromotropic acid (l,8-dihydroxynaphthalene-3,6-di-sulfonic acid). In this case, also, the dye is highly soluble and separates slowly from the unreacted chromotropic acid so that considerable care must be exercised. 

The reaction of di- and polysulfonic acids can usually be carried out so that the replacement of the sulfo groups by hydroxyls takes place stepwise (partial alkali fusion). Thus, phenol-m-sulfonic acid is obtained from benzene-m-disulfonic acid under mild conditions, while resorcinol is formed under more vigorous conditions (see page 144) similarly, naphthalene-l,5-disulfonie acid yields, first, l-naphthol-5-sulfonic acid, then l,5 dihydroxynaphthalene, both valuable azo dye... 

The rfaphthalenesulfonic acids find very little direct use in the preparation of dyes, but they are of great technical importance as steps in the preparation of important intermediates such as /3-naphthol and 3-naphthylamine, dihydroxynaphthalenes and aminonaphthols, and numerous naphthylamine-, naphthol-, and aminonaphthol-sulfonic acids. 

Sulfite during the conversion of naphthalene-l-sulfonate to 1,2-dihydroxynaphthalene (Kuhm et al. 1991). 

Intorre and Martell (237) have also studied the formation of mixed chelate species in which the zirconium 1 1 complex with the hexa-dentate chelating ligands, ethylenediaminetetraacetic acid, iV-hydroxy-ethylethylenediaminetriacetic acid, and m7 s-cyclohexanediaminetetra-acetic acid, are shown to take up one mole of the bidentate ligands, l,2-dihydroxybenzene-3,5-disulfonate l,8-dihydroxynaphthalene-3,6-disulfonate 8-hydroxyquinoline-5-sulfonate, and acetylacetone (except ZrHEDTA), to form 8-coordinate 1 1 1 species. At least for the zir-conium-EDTA-l,2-dihydroxybenzene-3,5-disulfonate species, there is evidence for dimerization (230). Additionally, the Zr EDTA complex reacts with one mole of the bidentate ligands, 5-sulfosalicyclic acid, alizarin sulfonate, citric acid, and lactic acid to form 1 1 1 complexes tartaric acid and pyrophosphate ions form complexes which could not be identified. The zirconium-nitriloacetic acid complex in the presence of two moles of oxalic acid or l,2-dihydroxybenzene-3,5-sulfonate also forms 1 1 1 complexes in solution. 

In copolymers consisting of 2,6-difluorobenzo-nitrile, with 2,8-dihydroxynaphthalene-6-sulfonate... 

Naphthol 2-Naphthol-8-sulfonate 2-Naphthol-6-sulfonate 1.7- Dihydroxynaphthalene 2.7- Dihydroxynaphthalene 2-Anthrol 0.1 ... 

The dyestuffs 3-( -nitrophenylazo)-4 -hydrox5maphthalene-l-sulfonic acid, l-(/)-nitrophenylazo)-2-hydroxy-3,6-disulfonic acid and 3-( -nitrophenyl-azo)-l,8-dihydroxynaphthalene-3,6-disulfonic acid (Chromotrope 2B, C.I. Acid Red 176) can be used as reagents for Mg. With these reagents, a spot test on filter paper is possible Idn. Limit 0.1 y Mg),... 

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