Acid dyes pyrazolone

Solid-phase acidic dyes ai e also used in the study of the ternai y systems with pyrazolone derivatives. In addition, the colorless complex of the investigated metals with pyrazolone derivatives has been studied by means of the metal-indicator method. 

Merocyanines belong to the class of nonionic methine dyes combining two nuclei, one of which is a ketomethylene of acidic nature such as pyrazolone, rhodanine, oxazolone, thiohydantoin,. 

Acid YeUow 23 (31), commonly known as Tartraziae, stiU maintains sales of nearly 0.5 million /yr ia the United States. It was first discovered ia 1884 and is made by coupling equimolar quantities of diazotized sulfarulic acid to 3-carboxy-l- -sulfophenyl)-5-pyrazolone. Other monoazopyrazolone dyes of commercial importance iaclude Acid YeUow 17 (32) (sulfarulic acid — l-(2,5-dichloro-4-sulfophenyl)-3-methyl-5-pyrazolone and Acid YeUow 40 [6372-96-9] (33) (Cl 18950) (p-aminophenol l-(4-chloro-2-sulfophenyl)-3-methyl-5-pyrazolone) foUowed by esterification of the phenoUc hydroxy group with -toluenesulfonyl chloride. 

In mordant dyes, phenols, naphthols, and enolizable carbonyl compounds, such as pyrazolones, are generally the couplers. As a rule, 2 1 metal complexes are formed ia the afterchroming process. A typical example of a mordant dye is Eriochrome Black T (18b) which is made from the important dyestuff iatermediate nitro-l,2,4-acid, 4-amiQO-3-hydroxy-7-nitro-l-naphthalenesulfonic acid [6259-63-8]. Eriochrome Red B [3618-63-1] (49) (Cl Mordant Red 7 Cl 18760) (1, 2,4-acid — l-phenyl-3-methyl-5-pyrazolone) is another example. The equiUbrium of the two tautomeric forms depends on the nature of the solvent. 

These dyes are invariably monoazo compounds with the reactive system attached to the diazo component, owing to the ready availability of monosulphonated phenylenediamine intermediates. Pyrazolone couplers are most commonly used, as in structure 7.82 (where Z is the reactive grouping), and this is particularly the case for greenish yellow vinylsulphone dyes. Catalytic wet fading by phthalocyanine or triphenodioxazine blues is a characteristic weakness of azopyrazolone yellows (section 3.3.4). Pyridones (7.83), barbituric acid (7.84) and acetoacetarylide (7.85 Ar = aryl) coupling components are also represented in this sector, with the same type of diazo component to carry the reactive function. 

In 1884, H.J. Ziegler first used pyrazolones as coupling components. In an attempt to find a new dye by synthesizing a colored osazone from phenyl hydrazine-4-sulfonic acid and dioxo tartaric acid, he obtained yellow tartrazine by condensation ... 

Fig. 3.12. Synthesis of the compounds by the methods (a) and (b). A = -NHC6H4S03H (dye la) A = -NHCH2CH=CH (dye lb) A = -OCH2CH=CH2 (dye lc). SP = N-(4 -sulpho)phenyl-3-methy 1-5-pyrazolone m-PDA = l,3-phenylendiamine-4-sulphonic acid. Reprinted with permission from T. Konstantinova et al. [90],...

Azo couplings with C-H acidic compounds such as barbituric acids (40) or pyrazolones (304) proceed equally quantitatively in the solid state. However, in some combinations a basic catalyst has to be added in the form of gaseous trimethylamine in order to speed up the reaction. The free azo dyes occur in the hydrazono form after washing away the unavoidable stoichiometric salts [99-100] (Scheme 46). The prescription should be carefully followed for safety... 

Tartrazine was separated by ion-pair HPLC from its subsidiary dye 3-carboxy-5-hydroxy-1 -p-sulfopheny-4-phenylazo-pyrazole disodium salt (195) and from its intermediates sulfanilic acid and l-(4-sulfophenyl)-3-carboxy-5-hydroxypyrazolone (pyrazolone-T) by means of TBA hydroxide (194,212). Ion-pair chromatography was also used for the determination of free and bound nonsulfonated aromatic amines in tartrazine after reduction with dithionite, diazotization with sodium nitrite, and coupling with R-salt (202). 

A method frequently used to determine aromatic amines in water-soluble dyes involves their extraction with chloroform, followed by diazotization of amines and coupling of diazonium salts with a reagent R-salt (disodium-3-hydroxy-naphthalene-2,7-disulfonate) or pyrazolone T (4,5-dihydro-5-oxo-l-(4-sulfophenyl-)l/7-pyrazole-3-carboxylic acid). The separated products are detected by UV-VIS spectrophotometry or fluorescence (210-212). 

Monoazo dyes with heterocyclic coupling components, such as pyrazolone or pyridone, are yellow to greenish yellow. Other suitable coupling components include aniline and naphthylamine derivatives. Substituted anilines or amino-naphthalenesulfonic acids are employed as diazo components. Examples are C.I. Reactive Yellow4, C.I. Reactive Yellow 17 (see Section 3.1.5). 

Acetoacetic acid arylides and pyrazolone derivatives are the coupling components mainly used. Naphtbolsulfonic acids are of only minor importance here. Dehydrothio- p-toluidine sulfonic acid (2) and the sulfonated primulin base are also used as diazo components for certain orange disazo direct dyes. 

Reaction of chlorosulfonic acid with mono- [141] or disazo dyes [142] yields sulfonyl chlorides, which can then be transformed into cationically substituted sulfonamides by reaction with dialkylaminoalkylamines. The coupling product of diazotized 2-anisidine with 2-hydroxynaphthoic acid arylide upon such treatment dyes paper red, and the azo dye from tetrazotized dianisidine and l-phenyl-3-methyl-5 -pyrazolone gives yellowish orange shades. 

Numerous cationic azo dyes are prepared by the action of /V-hydroxymcthyl-chloroacetamide on azo dyes in sulfuric acid medium, followed by displacement of the reactive chloro substituent by pyridine or trialkylamine. Of special significance for dyeing paper are dyes that are prepared by coupling of diazotized 2-(4 -aminophenyl)-5-methylbenzothiazole to acetoacetaiylides, pyrazolones, naphthols [143], or barbituric acid derivatives [144], followed by reaction with N-hydroxymethylchloro-acetamide and pyridine. The azo dye obtained by oxidative dimerization of 2-(4 -aminophenyl)-5-methylbenzothiazole may also be subjected to this conversion [145], Dye 51 colors paper yellow. 

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. 

First, 1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

C.I. Solvent Orange 56, [12227-68-8], simliar to C.I. Solvent Orange 5, 518745 1, [13463-42-8], which is a 1 1 chromium-complex dye, synthesized by di-azotizing 2-hydroxy-3-amino-5-nitrobenzenesulfonic acid and coupling to 1-phe-nyl-3 -m ethyl-5 -pyrazolon e. 

C.I. Solvent Yellow 82, [12227-67-7], similar to C.I. Solvent Yellow 21, [5601-29-6], 18690, which is a 1 1 chromium complex of the azo dye obtained from anthranilic acid and l-phenyl-3-methyl-5-pyrazolone. 

In the stepwise synthesis of the unsymmetrical complex dye 13 [ 70236-60-1] [10], the azo dye made from diazotized l-amino-2-hydroxy-5-nitrobenzene and 1-phenyl-3-methyl-5-pyrazolone and the 1 1 chromium complex obtained from 6-nitro-l-diazo-2-hydroxynaphthalene-4-sulfonic acid and 2-naphthol are heated together at 80 °C for 5 h. The adduct is salted out with NaCl. A black powder is obtained that dyes wool and leather in dark brown shades. The resulting colors are fast, particularly on shrink-resistant wool. 

C.I. Acid Blue 138 and C.I. Acid Red 138. Because it is well known that azo dyes derived from naphthol and pyrazolone intermediates exist predominantly in the hydra-zone form, this tautomeric form is given for Acid Yellow 42, Acid Red 151, Acid Red 138, and for the appropriate dyes that follow in this chapter. 

Polar yellow 5G is prepared by condensing p-chloro-m-sulfophenylhydrazine with acetoacetic ester, and coupling the resulting pyrazolone with diazotized p-aminophenol in acetic acid solution. The alkali sensitive dye which is formed is treated at 70°C. with p-toluenesulfonyl chloride, in the presence of soda and 1 mole of sodium hydroxide, to esterify the hydroxyl group. This esterification makes the dye insensitive to alkali and, at the same time, fast to milling on wool. 

This is the simplest member of the pyrazolone dyes which are prepared in two ways (a) from dihydroxytartaric acid and phenylhy-drazine (tartrazines), and (b) from phenylmethylpyrazolones by coupling with diazo compounds. The second method is simpler and has largely displaced the older, first method. The pyrazolone is prepared from a given phenylhydrazine (e.g., phenylhydrazinesulfonic acid, page 128) and acetoacetic ester, and coupled with diazotized aniline ... 

Sulfonation of pritnuline-like color bases by the baking process yields sulfonic acids whose azo dye derivatives are more fast to light than those from sulfonic acids prepared in the ordinary way. It is assumed that in the baking process, the sulfo group enters ortho to the amino group, and that this increases the light fastness. This same principle was mentioned in connection with the pyrazolone dyes. 

The pyrazolone azo dyes constitute an important group which arise from Ziegler s discovery in 1884 that a yellow dye, known as Tartrazine, was obtained by heating phenylhydrazine-/>-sulphonic acid with dihydroxy tartaric add ... 

The most important spectrophotometric methods for determining cyanide are based on the formation of polymethine dyes. These methods are highly sensitive and specific. The benzidine-pyridine method is often used. Lower colour stability is a drawback of the pyrazolone method. The barbituric acid method can also be recommended. 

Flavazin L has already been described as a textile dye derived from pyrazolone. Tartrazine 5 is one of the few synthetic dyes which are approved for colouring foodstuffs and cosmetics. The yellow compound, which is the trisodium salt, is produced by coupling 2,4-dihydro-3//-pyrazol-3-ones with diazo-tized sulfanilic acid. The required pyrazole is accessible from diethyl 2-oxobutanedioate and 4-hydrazinobenzene-1-sulfonic acid. 

The exact mechanism for intolerance to azo dyes and benzoates is still unknown. Since cross-reactions to various analgesics and anti-inflammatory drugs such as aspirin, indomethacin, dextropropoxyphene, phenylbutazone, menfenamate, ibu-profen, and sodium salicylate also occur, a nonallergic mechanism seems probable for most patients. A chemical resemblance can clearly be seen only between benzoates and salicylates (Fig. 1). When azo dyes are taken orally there will be an azo-reductive cleavage in the intestinal tract into sulfanilic acid and a pyrazolone derivative which can be further hydrolyzed to sulfophenylhydrazine (Ryan et al. 1969). Some azo dyes can form aniline compounds, which could explain their cross-reactions with preservatives (Walker 1970). 

Trace amounts of cyanide are usually determined by flow injection spectrophotometric procedures. The target species is first halogenated with chlora-mine-T, after which it reacts with a mixture of pyrazolone or barbituric acid and isonicotinic acid or pyridine to form a bluish-violet polymethine dye. The implementation of gas-diffusion modules in the flow setup for hydrogen cyanide separation avoids matrix interferences and enables the adaptation of inherently nonselective detectors, such as metallic silver-wire electrodes for potentiometric measurements. Total inorganic cyanide, including free and complexed species, such as iron-cyanide complexes, may be determined by sample decomposition with UV irradiation and further photometric or amperometric analysis. 

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