2- -l-naphthol-4-sulfonic

The ratio between the isomers obtained in coupling with 1,3- and 1,5-naphtholsulfonic acids depends on the reactivity of the diazo component. Energetic ones, such as the 2,4-dinitrobenzenediazonium compound, essentially couple only with l-naphthol-3-sulfonic acid [3771-14-0] in the para position, but 4-chloro-benzenediazonium salt (a weaker diazo) attacks the ortho position. Both isomers result when mononitrobenzenediazonium compounds are used. The tendency to couple para is greater in l-naphthol-5-sulfonic acid [117-59-9] C QHgO S (21). For the combination of... 

The l-naphthol-5-sulfonic acid is prepared by alkali fusion, at 160-190 C., of naphthalene-1,5-disulfonic acid (see page 219) it can also be prepared by the Bucherer reaction from l-naphthylamine-5-sulfonic acid (see page 214). 

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... 

L acid. (l-naphthol-5-sulfonic acid). C10H6(OH)SO3H. 

FIGURE 23. Absorption and fluorescence spectra of the acid form of l-naphthol-5-sulfonate (5S1N)... 

As a final example we compare the photoacidities of l-naphthol-5-sulfonate and 1-naphthol 5-tetrabutyl. The Forster cycle of the two photoacids was measured in methanol. The 5-position of the 1-naphthol system is considered the most sensitive to substituents (Table 12.4). As discussed in the HPTS case the sulfonate... 

The alternative approach is based on coupling gas diffusion and spectrophotometric detection, through monitoring the color change of acid-base indicators such as cresol red [47], 4-(2, 4 -dini-trophenylazo)-l-naphthol-5-sulfonic acid [48], bromothymol blue(BTB) [50], or the color fading of a phenolphthalein solution [45], all of them used as acceptor solution for the collection of the permeated CO2. Several environmental applications are reported in the literature. 

C10H7O5NS Metal ion 2-Nitroso- l naphthol- 5-sulfonic acid (nitroso... 

N-Ac [3819-12-3]. Solochrome fast blue B. 8-Acetamido-2-(2-hydroxy-3f5,6-trichlorophenylazo)-l-naphthol 5-sulfonic acid. Eriochrome navy blue BRL. Metachrome brilliant blue BL. Metomega chrome cyanine BLL. C.L 17940. 

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