Naphthionic acid

Place a mixture of 25 g. of a-naphthylamine (Section IV,37) and 125 g. (69-5 ml.) of concentrated sulphuric acid in a 250 ml. conical or round-bottomed flask, and heat in an oil bath for 4-5 hours or until a test sample, when made alkaline with sodium hydroxide solution and extracted with ether, yields no naphthylamine upon evaporation of the ether. Pour the warm reaction mixture cautiously and with stirring into 300 ml. of cold 

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I-Naphthylamine readily diazotizes and couples to aromatic hydroxylic or basic compounds. It was thus used as a first component in a number of important monoazo dyes, but its use has been severely curtailed because of its potent carcinogenicity. It sulphonates to give naphthionic acid (l-naphthylamine-4-sul-phonic acid). 

The sulphonic acids are usually prepared by the action of sulphuric acid upon a compound. The concentration of the acid and the temperature of reaction are varied according to the reactivity of the compound. Often oleum is used or even chiorosulphonic acid. Alternatively sulphur trioxide complexed to pyridine or dioxan can be used with reactive substrates. Aminosulphonic acids such as sulphanilic and naphthionic acids are most conveniently prepared by heating the sulphate of the amine at ISO C. 

Acid Brown 14 (27) (2 mol of naphthionic acid, ie, 4-amino-1-naphthalenesulfonic acid 1 mol resorcinol) and Acid Black 1 (28). Two other azo acid blacks. Acid Black 52 (43) and Acid Black 63 (44) are both metallized with chromium. 

Certain dyes when appHed by the afterchrome method are oxidized prior to metal complex formation. Examples iaclude. Chromotrope EB [3567-69-9] (52) (Cl Acid Red 14 Cl 14720) (naphthionic acid — l-naphthol-4-sulfonic acid) ia which a hydroxyl group is iatroduced by oxidation at the... 

Direct dyes are defined as anionic dyes substantive to ceUulosic fibers (cotton, viscose, etc), when applied from an aqueous bath containing an electrolyte. Before the discovery of Congo Red in 1884, only mordanted cotton could be dyed. Congo Red [573-58-0] (62) (Cl Direct Red 28 Cl 22120) a primary symmetrical disazo dye, which is made readily from bisdiazotized benzidine and naphthionic acid [84-86-6] (4-arnino-l-naphthalenesulfonic acid), was the precursor of a most important line of dyes, including all shades, derived from benzidine and its homologues. Today, no benzidine dye is produced because benzidine is carcinogenic. 

Fig. 5. Direct red dyes, (a) Direct Red 81 described ia text (68) (b) Direct Red 2 (o-toLidiae coupled to two moles of naphthionic acid) (69) (c) Direct Red 23 (aniline coupled to 6,6 -ureylenebis-l-naplitliol-3-sulfonic acid with a second coupling with j aminoacetanilide) (70) and Direct Red 80 (2 mol 6-amino-3,4 -azobenzenedisulfonic acid coupled twice to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid) (73). Direct Red 24 (4-aniino-y -toluenesulfonic acid coupled under acidic conditions to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid followed by an alkaline coupling of o-anisidine) (71) (d) Direct Red 72 (Broenner s acid, ie, 6-artiino-2-naphthalenesulfonic acid coupled under acidic conditions to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid followed by an...

Naphthionic acid (4-aminonaphthalene-l-sulfonic acid) [84-86-6] M 223.3, m > 300°(dec), pK 2.68. It crystallises from H2O as needles of the 0.5 hydrate. Salt solns fluoresce strongly blue. 

Table 3.6 Substantivity and structure of p-substituted monoazo naphthionic acid derivatives [68]...

Probtem 18.63 Synthesize from naphthalene and any other reagents (a) naphthionic acid (4-amino-l-naphthalenesulfonic acid), (b) 4-amino-l-naphthol, (c) 1,3-dinitronaphthalene, (d) 1,4-diaminonaphthalene, (e) 1,2-dinitronaphthalene. Do not repeat the synthesis of any compound. ... 

Alphanaphthy la mines ulphonic Acid Naphthionic Acid)... 

Ion-pair HPLC (194,195) was used to separate amaranth from its subsidiary dye l-(4-sulfo-l-naphthylazo)-2-naphthol-6-sulfonic acid disodium salt (fast red E) and from its intermediates 1-naphthylamine 4-sulfonic acid (naphthionic acid) and 2-naphthol-3,6-disulfonic acid disodium salt (R-salt). Ion-pair HPLC was also used for the determination of total free and bound nonsul-fonated aromatic amines in amaranth after diazotization and coupling with R-salt (198). 

Bailey et al. (199) and Singh (200) used ion-exchange HPLC for the separation of amaranth from the intermediates naphthionic acid and R-salt, as well as the side reaction products 2-naph-thol-6-sulfonic acid sodium salt (Schaeffer s salt), 2-naphthol-6,8-disulfonic acid disodium salt (G-salt), and 2-naphthol-3,6,8-trisulfonic acid trisodium salt (NTSA). 

Naphthols and Naphtholsulfonic Acids as Coupling Components. This series includes two important acid dyes with very similar structures C.I. Acid Red 88 (see Section 3.9.3), derived from diazotized naphthionic acid and 2-naphthol, and C.I. Acid Red 13, 16045 [2302-96-7] (2), from naphthionic acid and Schaffer s acid. Both are all-purpose dyes which, because of their attractive red shades, are still in use today in many areas of textile dyeing and also for leather and paper dyes. Wool dyeings produced with these dyes exhibit moderate fastness levels. 

Sulfo and Sulfamido Groups. It has been shown that sulfanilic acid can be converted into p-sulfophenylarsonic acid (25-45%).49 60 By the ordinary Bart reaction p-sulfamidophenylatsonic acid (25%) may be prepared,60 although a better yield (57%) is obtained by a modified Scheller reaction.18 Apparently, metanilic acid and naphthionic acid will not yield the corresponding arsonic adds.18 61 Although m-sulfamido-phenylarsonic add is not available by the usual procedure it can be prepared in a 58% yield by the method of Scheller.18... 

In these studies adult, male Wistar rats were fed purified hydrated gelatin diets containing either no fiber or 15% cellulose, lignin, metamucil, or pectin (16). After 28 days on the diet the animals received a single oral dose of Amaranth (1 mmole/kg). Blood samples were collected at various times and the plasma concentration of naphthionic acid (NA), the major microfloral metabolite of... 

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