Naphtholsulfonic acids

Many aminonaphthalenesulfonic acids are important in the manufacture of azo dyes (qv) or are used to make intermediates for azo acid dyes, direct, and fiber-reactive dyes (see Dyes, reactive). Usually, the aminonaphthalenesulfonic acids are made by either the sulfonation of naphthalenamines, the nitration—reduction of naphthalenesulfonic acids, the Bucherer-type amination of naphtholsulfonic acids, or the desulfonation of an aminonaphthalenedi-or ttisulfonic acid. Most of these processes produce by-products or mixtures which often are separated in subsequent purification steps. A summary of commercially important aminonaphthalenesulfonic acids is given in Table 4. 

Naphthalenol also is used ia the preparation of azo, iadigoid, and nitro, eg, 2,4-dinitro-l-naphthol, dyes, and ia making dye iatermediates, eg, naphtholsulfonic acids, 4-chloro-1-naphthalenol, and l-hydroxy-2-naphthoic acid. 1-Naphthalenol is an antioxidant for gasoline, and some of its alkylated derivatives are stabilizers for plastics and mbber (68). 

The principal uses for 2-naphthalenol are in the dyes and pigments industries, eg, as a coupling component for azo dyes, and to make important intermediates, such as 3-hydroxy-2-naphthalenecarboxyhc acid (BON) (28) and its anilide (naphthol AS), 2-naphtholsulfonic acids, aminonaphtholsulfonic acids, and l-nitroso-2-naphthol/77/-5 /-5(/ (29). 

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... 

It is well known that the rates of all azo coupling reactions in aqueous or partly aqueous solutions are highly dependent on acidity. Conant and Peterson (1930) made the first quantitative investigation of this problem. They demonstrated that the rate of coupling of a series of naphtholsulfonic acids is proportional to [OH-] in the range pH 4.50-9.15. They concluded that the substitution proper is preceded by an acid-base equilibrium in one of the two reactants, which was assumed to be the equilibrium between the diazohydroxide and the diazonium ion, in other words, that the reacting equilibrium forms are the undissociated naphthol and the diazohydroxide. 

Fig. 12-3. Rate of azo coupling of 4-toluenediazonium ion with 2,6-naphtholsulfonic acid as a function of pH (Zollinger, 1991).

Table 12-3. Kinetic hydrogen isotope effects found in azo coupling reactions of 4-chlorobenzene-diazonium ion with naphtholsulfonic acids (Zollinger, 1955 a Ernst et al., 1958).

More recently, Bagal and coworkers (Luchkevich et al., 1991) obtained similar results in a kinetic investigation of the coupling reactions of some substituted benzenediazonium ions with 1,4-naphtholsulfonic acid, and with 1,3,6-, 2,6,8-, and 2,3,6-naphtholdisulfonic acids. The kinetic results are consistent with the transient formation of an intermediate associative product. The maximum concentration of this product reaches up to 94% of the diazonium salt used in the case of the reaction of the 4-nitrobenzenediazonium ion with 1,4-naphtholsulfonic acid (pH 2-4, exact value not given). The authors assume that this intermediate is present in a side equilibrium, i. e., the mechanism of Scheme 12-77 mentioned above rather than that of Scheme 12-76, and that the intermediate is the O-azo ether. 

Naphthol AS pigments, 9 425 Naphthol couplers, 19 252-253 in chromogenic chemistry, 19 251 a-Naphthol derivatives, 21 145 P-Naphthol derivatives, 21 145 Naphthol dyes, 9 182, 407 08 Naphthol reds/maroons, 19 437-438 Naphtholsulfonic acids, 9 356 N aphthopyrans... 

Naphtholsulfonic acids mainly couple at the 2-position. The 4-coupling products obtained as byproducts must be carefully removed from the azo dyes, because unlike the 2-substitution products, their shade changes as a function of the pH value (shade intensification with rising pH due to formation of phenolate or naphtholate resonance structures). 

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. 

Primary disazo dyes of the type K <—D —>K2 (Ki = K2 or K i K2). This series includes many milling dyes because of the molecular size achieved (group C). Depending on the type of coupling components Ki and K2, which may be phenols, pyrazolones, acetoacetic acid arylamides, or naphtholsulfonic acids, clear yellow to red shades are obtained. For a long time the preferred diazo components were diaminodiphenyl derivatives, such as benzidine, o-tolidine and o-anisidine. They are now of no further importance because of their carcinogenic potential. 

As with some of the other methods, one of the reagents, i.e., amino-naphtholsulfonic acid, acts as recipient for the material dialyzed from the sample. The molybdate reagent is added to the acceptor stream after the dialyzer, mixed, and heated, and the developed color is read and recorded in the usual manner. 

It is claimed in a recent patent that ferrous hydroxide is a reagent of considerable value for the deamination of certain aminonaphtholsul-fonic acids.124 From 3-hydroxy-4-aminonaphthalenesulfonic add, 90-96% yields of the naphtholsulfonic acid are reported the product, however, is not isolated. Aniline gives not only benzene but also phenyl azide and biphenyl in unspecified yields.123... 

Coupling is carried out with a 0.1 N diazotized aniline solution, just as prescribed for H acid, and at the end the dye is salted out in the reaction dish so that the remainder of the naphtholsulfonic acid is easily determined. Starting out with a 2.24-gram sample, the volume of diazotized aniline in cubic centimeters gives the per cent purity directly. Coupling should be carried out at 0°C. 

Schaeffer salt, R salt, and other naphtholsulfonic acids are analyzed in exactly the same manner. Sultones, on the other hand, must first be split by hot sodium hydroxide. 

One gram of the sulfonic acid from the hydrosulfite reduction is boiled under reflux with 20 cc. 10 per cent hydrochloric acid. After a short time, the solution can be oxidized by air or an oxidizing agent to produce the characteristic red color obtained from 7-amino derivatives of l-amino-8-naphtholsulfonic acids. Since it is known that the Polar dyes contain the toluenesulfonyl group, it may be assumed that the acyl residue connected to the N is the p-toluenesulfonyl group. 

Neville-Winter acid. (l-naphthol-4-sulfonic acid a-naphtholsulfonic acid NW acid). 

Schaeffer acid. (2-naphthol-6-sulfonic acid (3-naphtholsulfonic acid). 

Naphtholsulfonic acids. The sodium salts of the following naphtholsulfonic acids were studied quantitatively by L. J. Desha, R. E. Sherill, and L. M. Harrison. ... 

Desha and his collaborators have studied also resorcinol- and hydroquinonesulfonic acids. The fluorescence of these compounds is much less marked than that of the naphtholsulfonic acids. Their rapid decomposition in alkaline solutions renders them valueless. 

This brief and necessarily incomplete review of fluorescence indicators must sufl ce. A more quantitative discussion of the subject would be premature at present because too many factors, such as salt error, effect of indicator concentration, etc., remain yet to be studied exhaustively. Chlorides, for example, diminish considerably the fluorescence of the quinine cations and of the naphtholsulfonic acid anions. Fluorescence indicators are as yet... 

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