Pyrocatechol-33-disulfonic acid

Diazo coupling involves the N exocyclic atom of the diazonium salt, which acts as an electrophilic center. The diazonium salts of thiazoles couple with a-naphthol (605). 2-nitroresorcinol (606), pyrocatechol (607-609), 2.6-dihydroxy 4-methyl-5-cyanopyridine (610). and other heteroaromatic compounds (404. 611) (Scheme 188). The rates of coupling between 2-diazothicizolium salts and 2-naphthol-3.6-disulfonic acid were measured spectrophotometrically and found to be slower than that of 2-diazopyridinium salts but faster than that of benzene diazonium salts (561 i. The bis-diazonium salt of bis(2-amino-4-methylthiazole) couples with /3-naphthol to give 333 (Scheme 189) (612). The products obtained from the diazo coupling are usuallv highly colored (234. 338. 339. 613-616). 

Abbreviations DHG = Ar,Ar-di(2-hydroxyethyl)glycine NTA = nitrilotriacetic acid EDTA = ethylenediaminetetraacetic acid tiron = pyrocatechol-3,5-disulfonic acid BAL = 2,3-dimercaptopropanol unithiol = sodium 2,3-dimercaptopropane sulfonate tren — triaminatriethylamine penten = tetrakis(aminoethyl)ethylenediamine bipy = 2,2 -bipyridyl phen = 1,10-phenanthroline. 

Pyrocatechol-3,5-disulfonic acid disodium salt (Tiron)... 

Pyrocatechol, see B-00020 Pyrocatechol-3,5-disulfonic acid, see T-00186 Pyrocatecholphthalein, see P-00220 Pyrocatecholsulfonephthalein complexan,... 

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