1 - Amino-8-naphthol-2,4-disulfonic

Solvent of arystallization, 42 Solvents distilling off, 21 for recrystallization, 35 Spiral gas washing bottle, 62 Spot test reagents, 396 SS acid (Chicago add), see 1-Amino-8-naphthol 2,4-disulfonic add... 

Using this procedure, other diamines such as benzidine and dianisidine may be diazotized and coupled with other amino-naphthols, such as S acid (i-amino-8-naphthol-4-sulfonic acid), J add (2-amino-5-naphthol-7-sulfonic add). Gamma add (2-amino-8-naphthol-6-sulfonic add), and H add (i-amino-8-naphthol-3,6-disulfonic acid), or with simple naphthols such as NW add (i-naphthol-4-sulfonic add), Schaeffer s add (2-naph-thol-6-sulfonic acid), and R add (2-naphthol 3,6-disulfonic add). The procediue would be varied only in the manner of salting out the dyes, each of which would require a set of optimum cond tions... 

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). 

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])... 

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... 

Azo Dyes. The dye obtained by coupling diazotized 4-(2-sulfooxyethylsulfonyl)ani-line with l-amino-8-naphthol-3,6-disulfonic acid at pH 1 - 2 is coupled at pH 6 - 7 with a diazonium compound synthesized from the condensation product derived from l,3-diaminobenzene-6-sulfonic acid and 2,4,6-trifluoro-5-chloropyrimidine. The crude material is salted out of the solution and isolated. This product (24) gives a blue solution in water and dyes cotton in a marine blue to black color ... 

Sulfurous acid and its salts are inexpensive reducing agents which are, however, usable only in special cases. These reagents frequently give sulfonation simultaneously with reduction (cf. the preparation of l-naphthylamine-2,4-disulfonic acid from 1-nitronaphthalene, and of l-amino-2-naphthol-4-sulfonic acid from nitroso- -naphthol, pages 178 and 201). Also, in the reduction of diazobenzene to phenylhydrazine, a N-sulfonic acid is formed first and this must be split by vigorous treatment with hydrochloric acid (see pages 96 and 128). 

Amino-8-naphthol-6-sulfonic add, 204, 207, 208, 286 Aminonaphtholsulfonic adds, determination, 389 p-Aminophenol, 78 2-Aminophenol-4,6-disulfonic add, 153... 

SODIUM DISULFITE see SIIOOO SODIUM DITHIONITE (DOT) see SHR500 SODIUM DITOLYLDIAZOBIS-8-AMINO-1-NAPHTHOL-3,6-DISULFONATE see CMO250 SODIUM DITOLYLDIAZOBIS-8-AMINO-1-NAPHTHOL-3,6-DISULPHONATE see CMO250 SODIUM DODECYLBENZENESULFONATE (DOT) see DXW200... 

The azo compounds are important chromophores because of extended electronic delocalisation between the two aromatic rings via the azo bond. The darkness of the dye is enhanced by extensive delocalisation combined with several sulfonic acid groups which function as auxochromes. An example is provided by Naphthol Blue Black B (10), prepared from 8-amino-l-hydroxynaphthalene-3,6-disulfonic acid (H-acid) (11) by coupling it in the 7-position with diazotised p-nitroaniline in acidic solution and subsequently coupling in the 2-position with diazotised aniline in alkaline solution (Scheme 3). The H-acid (11) is a very versatile component in dye manufacture because it can couple with diazonium salts in either the 2-position or 7-position depending on the pH of the reaction medium, as indicated in Scheme 3. 

B acid. (l-amino-8-naphthol-3,5-disulfonic acid). C10H4NH2OH(SO3H)2. 

Chicago acid. (l-amino-8-naphthol-2,4-disul-fonic acid 8-amino-l-naphthol-5,7-disulfonic acid SS acid 1,8,2,4-acid 2-sulfur acid). 

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