Naphthols 2-naphthol-3,6-disulfonate

The kinetic study of the dissociation of 2-naphthol disulfonate is hampered by some technical limitations. The emission of the OH is at a short wavelength, which is already absorbed by the optical components of... 

The slow decay of 4>OH would be accompanied by a comparable slow rise of 0 which is not the case. The rise time of < )0 emission of 2-naphthol disulfonate—bovine serum albumin complex was as fast as measured for the free ligand (Ir se 100 psec). This discrepancy implies that the species that we observe is not formed in the site where... 

Synonyms AF red no. 1 Cl 16155 Cl food red 6 Cl food red 6, disodium salt D C Red No. 15 Disodium 3-hydroxy-4-((2,4,5-trimethylphenyl) azo)-2,7-naphthalenedisulfonate Disodium 3-hydroxy-4-((2,4,5-trimethylphenyl) azo)-2,7-naphthalenedisulfonic acid Ext. D C Red No. 15 FD C Red No. 1 3-Hydroxy-4-((2,4,5-trimethylphenyl) azo)-2,7-naphthalenedisulfonic acid, disodium salt Japan red 1 Maple ponceau 3R Ponceau RN Scarlet F Sodium cumeneazo-P-naphthol disulfonate... 

CasHaaSgOiiSg Oarbonyl-bis-[8-(3-amino-cinnamoylamino)-naphthol-(l)-disulfon> 8aure-(3.5)] 14 1757. 

Carbonyl-bi8- 8-[3-(3-ammo-anisoylamino)-benzolsulfamino]-naphthol (l)-disulfon saure-(3.6) 14 I 760. 

Nitroso-R salt is the disodium salt of a-nitroso-/ff-naphthol-disulfonic acid. This reagent reacts with Co in the same manner as a-nitroso-)5-naphthol, but it is water-soluble. A highly sensitive spot test is based on the formation of the red cobalt complex of this reagent on an ion-exchange resin. 

Naphthol-6,8-disulfonic acid. p-Naphthol-y-disulfonic acid. 

Naphthol-3,6-disulfonic acid, see H-00342 2-Naphthol-6,8-disulfonic acid, see H-00343 -Naphthol-y-disulfonic acid, see H-00343... 

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). 

Naphthol-3,6-disulfonic acid 9.0 to 9.5 Dark blue to light blue 4... 

Technologically, the most important examples of such couplers are 1-naphthylamine, 1-naphthol, and sulfonic acid derivatives of 1-naphthol (Fig. 2). Of great importance in the dyestuff industry are derivatives of l-naphthol-3-sulfonic acid, such as H-acid (8-amino-l-naphthol-3,6-disulfonic acid [90-20-0])... 

Pontacyl Carmine 2G (Acid Red 1, Amido Naphthol Red G, Azophloxine, l-acetamido-8-hydroxy-7-phenylazonaphthalene-3,7-disulfonic acid di-Na salt) [3734-67-6] M 510.4, Cl 18050, X.max 532nm. Salted out three times with sodium acetate, then repeatedly extracted with EtOH. See Solochrome Violet R on p. 352 in Chapter 4. [McGrew and Schneider 7 Am Chem Soc 72 2547 1950.]... 

The rate constants in Figure 5-3 were measured by injecting the solution of the (E)-diazoate into a buffer solution that also contained a highly reactive coupling component (2-naphthol-3,6-disulfonic acid, except at pH values below 2.5, where l,8-dihydroxynaphthalene-3,6-disulfonic acid was used instead). The diazonium ion formed reacts rapidly with these naphthols, and the concentration of the corresponding azo compounds was determined spectrophotometrically. 

A quantitative study of the azo coupling reactions of heterocyclic diazo compounds was made by Sawaguchi et al. (1971), who measured the coupling rates of seventeen heterocyclic diazonium ions with R-acid (2-naphthol-3,6-disulfonic acid) and compared them with those of the benzenediazonium ion with the same coupling component. All the heterocyclic diazonium ions investigated react faster with R-acid than does the benzenediazonium salt. More recently, Diener and Zollinger (1986) confirmed Sawaguchi s results and interpreted them in more detail. 

The pK values for azolediazonium ions (Scheme 12-4) refer to the heterolysis of the NH bond, not to the addition of a hydroxy group. Therefore, these heteroaromatic diazo components may react either as a cation (as shown in Scheme 12-4) or as the zwitterion (after loss of the NH proton). Diener and Zollinger (1986) investigated the relative reactivities of these two equilibrium forms (Scheme 12-5) in the azo coupling reaction of l,3,4-triazole-2-diazonium ion with the tri-basic anion of 2-naphthol-3,6-disulfonic acid. 

The secondary a-deuterium isotope effects on azo coupling reactions are small, i.e., km/kiv is very close to unity. For the reaction of the 4-nitrobenzenediazonium ion with the trianion of l-D-2-naphthol-6,8-disulfonic acid catalyzed by pyridine, km/kiv = 1.06 0.04 (Hanna et al., 1974). 

Zollinger (1971) calculated the actual rate constant referring to the monomeric diazo component from the (overall) measured rates and the dimerization equilibrium constant. The ratio of rates of the first to the second azo coupling reaction of the biphenyl-4,4 -bis-diazonium ion with the trianion of 2-naphthol-3,6-disulfonic acid at 15 °C, k /k2 9 is 80. 

In the reaction of the strongly electrophilic 4-nitrobenzenediazonium ion with 2-naphthol-6,8-disulfonic acid, which yields a sterically hindered o-complex, Roller and Zollinger (1970) actually observed the rapid formation of a 7T-complex spec-trophotometrically at low pH. The concentration of the 7T-complex decreases slowly and at the same rate as that of the formation of the azo product. H NMR data indicate that the 7t-complex is not localized. All 7T-electrons of the benzene and the naphthalene system are involved in the complex formation to a similar degree, in... 

Bagal et al. (1975) investigated in more detail the role of donor-acceptor complexes in the azo coupling reaction of the 4-nitrobenzenediazonium ion with 2-naphthylamine-3,6-disulfonic acid and that of the 4-chlorobenzenediazonium ion with 2-naphthol-6-sulfonic acid. Their kinetic results are, as would be expected, compatible with the mechanisms shown in Schemes 12-74 or 12-75. 

Micellar catalysis of azo coupling reactions was first studied by Poindexter and McKay (1972). They investigated the reaction of a 4-nitrobenzenediazonium salt with 2-naphthol-6-sulfonic and 2-naphthol-3,6-disulfonic acid in the presence of sodium dodecylsulfate or hexadecyltrimethylammonium bromide. With both the anionic and cationic additives an inhibition (up to 15-fold) was observed. This result was to be expected on the basis of the principles of micellar catalysis, since the charges of the two reacting species are opposite. This is due to the fact that either of the reagents will, for electrostatic reasons, be excluded from the micelle. 

The yellow ink jet dyes (and pigments) are metal-free azo dyes, such as Cl Direct Yellow 132 and Cl Acid Yellow 23 (Tartrazine).48,49 Most of the magentas are azo dyes derived from H-acid (l-amino-8-naphthol-3,6-disulfonic acid), such as (62), and xanthenes, such as Cl Acid Red 52 and Cl Acid Red 289.48,49 Where high lightfastness is a requirement, a copper complex azo dye, Cl Reactive Red 23 (63), is used. However, such dyes are dull (see Section 9.12.3.2). Nickel complex PAQ dyes, such as (22), are claimed to be brighter and to have similar high lightfastness... 

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