Naphthylaminesulfonic acids

Naphtyl, n. naphthyl, -amin, n. naphthylamine. -aminsulfosaure, /. naphthylaminesulfonic acid, -blsu, n. naphthyl blue. 

In a more recent paper (Stovpovoi et al., 1991b) Bagal and coworkers interpret their observation that Arrhenius plots of the rates of various N- and C-couplings of aromatic amines (e. g., 1-naphthylamine, 2,6-naphthylaminesulfonic acid, and 4-me-thylaniline) are linear only in aqueous systems, but not in aprotic solvents such as nitromethane or acetonitrile. Their explanation is based on an extension of the clas-... 

Naphthylamines and Naphthylaminesulfonic Acids. The compounds shown in Figure 2.2, known by their common names, are examples of naphthylaminesulfonic acids. 

Naphthylamines, Naphthylam inesulfonic Acids. Some examples (35-38) are mentioned here other compounds can be found among the diazo components (see Figure 2.2), because most naphthylaminesulfonic acids can be employed both for diazotization and for coupling purposes. 

Whereas p -naphthylaminesulfonic acids always couple at the adjacent a position, in a-naphthylaminesulfonic acids, the coupling location is influenced by the position of the sulfonic acid group 1,6-, 1,7-, and 1,8-naphthylaminesulfonic acids couple at the 4-position 1,5-naphthylaminesulfonic acid (Laurent acid) only couples with very strong couplers (e g., 2,4-dinitroaniline), mainly at the 4-position. With diazotized aniline, chloroaniline, or diazotized aniline sulfonic acids the 2-aminoazo dyes are obtained, but with diazotized nitroaniline, mixtures of the 2-and 4-coupling products form (Scheme 2.1). 

The 1,6- and 1,7-naphthylaminesulfonic acids have long been very important as components for azo dyes, particularly as the middle component in polyazo dyes. They are used in the preparation of the important black cotton dyes of the type of Columbia black FF, and also of a whole series of developed dyes, such as the important naphthogene blue, Zambesi black V, and others. Sulfonic acids of this type are also frequently used in preparing dyes of the Sirius blue series (Bayer). 

The concentrated solution is made strongly acid to Congo red by the addition of about 100 cc. concentrated hydrochloric acid and left to crystallize for a day while being stirred continuously. Both of the Cleve acids (1,6- and 1,7-naphthylaminesulfonic acids) separate slowly, although they are rather insoluble in water once they have precipitated. After 24 hours, the precipitate is filtered off and washed thoroughly with a large volume of water. 

It is remarkable that yields higher than about 70 per cent of product titratable with nitrite are never obtained even in the most carefully executed preparations, even though all of the nitric acid is used (nitrometer determination). The reason must be that, in this case as well as in others, some of the amine is destroyed in the reduction. As in the preparation of H acid and the other naphthylaminesulfonic acids, it is always necessary to destroy the residual nitric acid before the reduction (see page 185). 

The method given above is suitable for all aminosulfonic and carboxylic acids which are difficultly soluble in dilute hydrochloric acid. If the amino acid is very insoluble, the addition of its solution to the acid should be made very slowly and with vigorous stirring. With some of the naphthylaminesulfonic acids which have a tendency to couple with themselves, it is desirable to add some of the nitrite to the hydrochloric acid before the amine is added. It is also advantageous to use an excess of nitrite in these cases, if it does not interfere in later steps or if it can be removed by filtering off the diazo compound. 

Further evaporation of the reduction mixture precipitates a second fraction whose properties are not very characteristic. This fraction is not a single compound. It gives no characteristic reaction with ferric chloride, showing the absence of a phenolic hydroxyl group, and it must be, therefore, a naphthylaminesulfonic acid or some other amino compound which gives no condensation product with phenanthrene-quinone. 

As a third fraction, a very easily soluble substance is obtained. This material gives a weak blue fluorescence in aqueous or weakly alkaline solution, resembling the fluorescence of naphthylaminesulfonic acids of the type of Freund acid, Laurent acid, or Acid IV. The substance can be diazotized and combined with R salt to produce a dye having two rather unsharp absorption bands at 515.8 and 490.8 m/ . These properties indicate that the reduction compound is Acid IV. 

Technical Observations. The pure 1,6- and 1,7-naphthylaminesulfonic acids give practically identical dyes. Frequently it is advantageous to use a mixture of the two acids because the resulting dyes are stronger, particularly in the case of black polyazo dyes (e.g., Columbia black or Zambesi black V). 

The nitration reaction is carried out in exactly the same way as in the preparation of Cleve acid, except that here the second addition of sulfuric acid is unnecessary since it was all added at the beginning. The reduction step and isolation of the two isomeric naphthylaminesulfonic acids are also carried out as described for Cleve acids. The sodium salt of the 1,8 acid is, however, still less soluble than that of the 1,7 acid, and the isolation is therefore easier. The 1,8 acid obtained is practically free from Cleve acids, although a small amount is always present despite the low sulfonation temperature used. The yield of 1,8 acid is equivalent to about 100 grams of 100 per cent material that of the 1,5 acid, obtained... 

It should be noted that many highly reactive diazonium salts (especially when in strong mineral acid solution) rapidly turn starch-iodide paper blue, and it is essential, therefore, to know the sensitivity of the paper used. Sulfanilic acid, metanilic acid, and naphthylaminesulfonic acids are diazotized at 15°C. Cleve acids cannot be determined so easily because they couple with themselves immediately. In this case, it is best to add the bulk of the nitrite to the neutral soluion and acidify the mixture with good stirring. The diazotization can also be carried out directly at 0°C., adding nitrite until the original violet color gives way to a pure brown. The indirect method is preferred, however, because it is more rapid. 

In the case of dyes having the first type of nucleus, Rigterink and France also found that those produced from /J-naphtholsulfonic acids are more adsorbable than dyes produced from a-naphthol-sulfonic acids. When an NH 2 group is substituted for an OH group, the situation is exactly reversed the dyes formed from a-naphthy-laminesulfonic acids are more adsorbable than those formed from /J-naphthylaminesulfonic acids. 

Sulfonation of / -naphthylamine leads to somewhat more precise orientation of the substituents. When special attention is paid to conditions such as temperature and S03 content of the sulfonation mixture, either 6- and 7-amino-l-naphthalenesulfonic acid or 6- and 7-amino-2-naphthylaminesulfonic acid can be obtained. When the concentration of S03 is increased, di- and tri-sulfonic acids of jS-naphthylamine are formed from the monosulfonic acids.151,152... 

For detailed reviews, see Encyclopedia of Chemical TechnologyNaphthalene-sulfonic Acids, Naphtholsulfonic Acids, Naphthylaminesulfonic Acids Lues, pp. 65fl. 

Naphthalenesulfonic acid P-naphtholsulfonic acid mfg. 2-Naphthalenesulfonic acid P-naphthylaminesulfonic acid mfg. 2-Naphthalenesulfonic acid body lotion additive Glyceryl polymethacrylate body rubs Isopropyl alcohol bodying agent... 

Zou et al. [1560] separated 14 phenylamine- and naphthylaminesulfonic acids (e.g., 2-aminonaphthalene-4,6,8-trisulfonic acid, l,3 diamino-4-sulfonic acid, phenylamine-2-sulfonic acid, 6-chlorophenylamine-3-sulfonic acid, naphthylamine-7-sulfonic acid) in 30 min on a Cjg column (A = 254 nm). Baseline resolution was achieved using an aqueous 10 mM phsophate buffer pH 6.8 mobile phase. The capacity ctors for these and 10 additional compounds belonging to these classes of compounds were tabulated. 

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