Sulfanilic diazotization

Most of the thiazoles studied absorb in the ultraviolet above 254 nm, and the best detection for these compounds is an ultraviolet lamp (with plates containing a fluorescent indicator). Other indicator systems also exist, among which 5% phosphomolybdic acid in ethanol, diazotized sulfanilic acid or Pauly s reagent (Dragendorff s reagent for arylthiazoles), sulfuric anisaldehyde, and vanillin sulfuric acid followed by Dragendorff s reagent develop alkylthiazoles. Iodine vapor is also a useful wide-spectrum indicator. 

Alkaline Coupling Process. Orange II [633-96-5] (21) (Cl Acid Orange 7 Cl 15510) a monoazo dye discovered ia 1876, serves as an example of the production of an azo dye by alkaline coupling. A suspension of diazotized sulfanilic acid (0.1 mol) is added to a solution (cooled to about 3°C) of 14.4 g 2-naphthol dissolved ia 15 g 30% sodium hydroxide, 25 g sodium carbonate, and 200 mL of water. The temperature should not be allowed to rise above 5°C. The reaction is heated until solution occurs and the dye is precipitated with 100 g sodium chloride. The mixture is cooled and filtered, and the product is dried. 

Of these dyes, Acid Yellow 151 (37) still has the greatest market among the yellows. As reported by USITC, production had increased to 1989 tons in 1985 from 706 tons in 1975. It is produced by coupling diazotized 2-amino-l-phenol-4-sulfonamide to acetoacetanilide followed by metallizing with cobalt to obtain a 1 2 cobalt complex. Acid Orange 24 (38), which is sulfanilic acid coupled to resorcinol to which diazotized mixed xyUdines have been coupled, is an unsymmetrical primary diasazo dye with a bihinctional coupling component. 

Chemists working with azo dyes use a shorthand designation based on the synthesis by azo coupling. It is characterized by an arrow from the amine used for diazotization (the so-called diazo component) to the coupling component, e. g., for 1.8 sulfanilic acid - 2-naphthol. This designation is especially useful for polyazo dyes (see Zollinger, 1991, p. 109). 

Monoaminoarenesulfonic acids exist in acid solution as zwitterions (2.3 in the case of sulfanilic acid), which are relatively insoluble in contrast to the corresponding bases (such as 2.4). For this reason the indirect method of diazotization is often employed in such cases. The aminoarenesulfonic acid is dissolved as the anion (2.4) by introducing the required amount of sodium carbonate or hydroxide, and nitrite is added to the approximately neutral solution, which is then run into mineral acid. Indirect diazotization is particularly recommended for the aminosulfonic acids of greater molecular mass but, contrary to some statements in the literature, the three anilinesulfonic acids themselves can be diazotized directly in suspension, the reaction proceeding quite smoothly after some practice. 

It has long been known that pyrroles can be used as coupling components (see, for example, Schofield, 1967, p. 76). More recently Butler and coworkers have studied the reactions of arenediazonium ions with pyrroles (Butler et al., 1977 Butler and Shepherd, 1978, 1980). 1-Methyl- and 2,5-dimethylpyrrole react with diazotized sulfanilic acid to give 12.34 and 12.35 respectively. The formation of 12.34 is in accordance with the a-positions in pyrrole being more susceptible to elec-... 

Fast blue salt B, fast blue salt BB, fast black salt K, diazotized sulfanilic acid (Pauly s reagent), diazotized sulfanilamide or 4-nitroaniline... 

Phenols (capable of coupling) Fast blue salt B, fast blue salt BB, fast black salt K, diazotized sulfanilic acid (Pauly s reagent) diazotized sulfanilamide or 4-nitroaniline Intensely colored azo dyes are formed. Catecholamines [20, 3S], imidazoles [21] and amines capable of coupling also react. [3, 17]... 

The specific detection of aromatic nitro compounds is a second example. These can be converted by reduction to primary amines, which are then diazotized and coupled to yield azo dyes (cf. reagent sequence Titanium(III) chloride — Bratton-Marshall reagent ). Sodium nitrite —naphthol reagent, diazotized sulfanilic acid and other reagents specific for amino groups (e.g. ninhydrin, fluorescamine, DOOB, NBD chloride [9]) can also be used in the second stage of the reaction (Fig. 21). 

Iodine-Sodium Carbonate-Sulfanilic Acid, Diazotized... 

The mechanism of the reaction has not been eiuddated. Presumably iodine eliminates the imidazole ring from N-substituted imidazole derivatives such as clotrimazole, and this then couples with diazotized sulfanilic acid to yield an azo dye. 

Sulfanilic Acid, Diazotized Reagent Sulfanilic Acid, Diazotized Reagent 403 ... 

Substances Sulfanilic acid —Hydrochloric acid (32%) longer periods [20]. Note The sulfanilic acid can also be diazotized in situ on nitrite-impregnated TLC lay- ... 

Sodium nitrite ers in this case the chromatograms are merely sprayed with sulfanilic acid solution (2% fTTlO mol hydrochloric acid) [5], Diazotized 4-nitroaniline can also be used in place of ... 

Note The sulfanilic acid can also ers in this case the chromatogram in 10 mol hydrochloric acid) [5]. I diazotized sulfanilic acid [3]. In tl alcoholic iodine solution to cleave sodium carbonate solution and f 2,4,6-Trichlorophenol and 2,3,4 The detection limits for phenol are 0.1-1 pg substance per chron The reagent can be used, for c lulose layers. 

The mixing in the first five cells is illustrated in Figure 15.16. In the fifth cell, after 50 ms, the reactants are very weU mixed. After the fifth ceU, only the temperature must be controlled to keep the reactants weU mixed [30]. The very good mixing properties were also verified with a mixing-sensitive reaction, that is, the mixing-sensitive diazo coupling between 1-naphthols, 2-Naphthols, and diazotized sulfanilic acid [30]. 

A) Diazo-coupling in a two-phase system using BCR diazotized sulfanilic acid the azo color, obtained in the aqueous phase, is determined photometrically... 

Diazotized sulfanilic acid (5 minutes, room BCR temperature)... 

In 1877, Lenz17 originated a general route to aryl fluorides. Heating diazotized sulfanilic acid 3 and hydrofluoric acid gave 4-fluorobenzenesulfonic acid (4) derivatives of the acid function were also made. 

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