Sulphanilic acid, diazotization

C HgNjOjS. Colourless needles, with iH20. Prepared by reducing diazotized sulphanilic acid with an excess of sodium sulphite. It is a typical hydrazine in its reactions with ketones, and with acetoacetic ester. The latter reaction gives rise to the tartrazine dyestuffs, and is much used commercially. 

Figure 5.3-7. Scheme of reaction between diazotized sulphanilic acid (B) and 1-naphthol (A). 

Example 5.4.5.1. Application of the E-model for simulation of the coupling of I-naphthol with diazotized sulphanilic acid in a semibatch reactor (after Baidyga and Bourne, 1989b). 

The complete reaction scheme is shown in Fig. 5.3-7, while Fig. 5.4-51 gives a simplified representation. 1-naphthol (A) is primarily coupled with diazotized sulphanilic acid (B) to form monoazo dyes coupled in para and ortho positions (p-R and o-R, respectively). This reaction is first order in both A and B. Each of the primary products can react with diazotized sulphanilic acid to form bisazo dye (5). Rate constants at 298 K and pH 10 are ku = 10600 m mof s k2i = 1 22 = 1.7 m mor s (see Fig. 5-4-51). 

Bilirubin is diazotized with para-sulphonyl benzene diazonium compound and the absorbance of the resulting azobilirubin is measured at 600 nm to determine bilirubin level in the biological fluid e.g., blood serum. In usual practice, a serum blank is run simultaneously by reacting the serum with caffeine, sulphanilic acid and tartaric acid, and the absorbance of the blank is measured at 600 nm which is subsequently subtracted from the azobilirubin absorbance initially obtained before the bilirubin level is finally determined. 

Bilirubin Diazotized sulphanilic acid (Ehrlich s Reagent) 540... 

Cram and Day 57> successfully synthesized a quinone of [2.2]para-cyclophane by coupling the phenol 148 with diazotized sulphanilic acid to give 149. Reduction of 149 gave the unstable aminophenol 150 on oxidation with ferric sulphate 150 afforded the quinone 30 in 68% overall yield. 

A photometric flow-through sensor for the determination of carbamate pesticides (carbofuran, propoxur and carbaryl) based on similar principles as regards the detector and sensor used (a diode array spectrophotometer and a flow-cell packed with C,g resin, respectively) was employed to monitor the formation of the products resulting from hydrolysis of the analytes and online coupling of the respective phenols with diazotized sulphanilic acid. This... 

AAP) 4-aminoantipyrine FDNB l-fluoro-2,4-dinitrobenzene DSA diazotized sulphanilic acid OPA 2-o-phthal-dehyde MCE 2-mercaptoethanol Dns 5-dimethylaminonaphtalene-l-sulphonyl. 

Other method was described by Wagner (1+6) for the analysis and detection of salicylic acid and derivatives including salicylamide. Development was effected by using color reactions, with ferric ammonium sulphate, ammoniacal silver nitrate solution, potassium nitrate, HC1 and 5% KOH through diazotization and coupling with, 2-naphthol and coupling with diazotized sulphanilic acid. 

Sulphanilic acid-a-naphthylamine reagent. (Griess-Ilosvay test) This test depends upon the diazotization of sulphanilic acid by nitrous acid, followed by coupling with a-naphthylamine to form a red azo dye ... 

It is known also as helianthine and as tropaeolin D. It is not prepared by starting with amino azo benzene but with sulphanilic acid which is para-amino benzene sulphonic acid. This is diazotized and then coupled with di-methyl aniline yielding the azo compound. 

Reagent for Nitrites in Water.— An illustration of such a reaction is one which is the basis of the colorimetric determination of nitrites in water. When sulphanilic acid, para-amino benzene sulphonic acid, is diazotized and the resulting diazo compound treated with alpha-naphthylamine the benzene ring and the naphthalene ring become coupled as an azo compound which is red in color. 

The most frequently used competitive reaction is the diazo-coupling of 1-naphthol with diazotized sulphanilic acid at a pH = 9.9, in which a single coupled (desired) and double coupled (undesired) products are formed (if the side-reaction in which the bis-azo-dye is decomposed due to the presence of excess diazonium ions is disregarded) ... 

The first acid dye containing an azo group appeared in 1876. It was prepared by coupling diazotized sulphanilic acid with /3-naphthol, and was known as Orange II (C.I. acid orange 7), formula (2) ... 

Interaction of sulphanilic acid and sodium carbonate gives the soluble sodium salt of sulphanilic acid, which upon diazotization yields the intermediate phenyl diazonium sulphonate. The resulting diazonium salt on reacting with dimethylaniline and sodium hydroxide produces the desired product methyl orange. 

Separately dissolve 3.025 g (3.15 ml 0.05 mol) of pure dimethylaniline in 1.5 ml of glacial acetic acid and now add it in small lots at intervals with vigorous stirring to the suspension of diazotized sulphanilic acid. 

Why is it important to carry out diazotization of sulphanilic acid between 0-5°C ... 

The potential use of diazotized [ I]di-iodosulphanilic acid as a label for cell-surface membranes has been investigated. Colorimetric determination of the compound is possible as it reacts at neutral pH with naphth-l-ol to yield a coloured complex (X ax 430 nm). Results obtained surest that when used under appropriate conditions di-iodo-sulphanilic acid can serve as a highly selective membrane label with minimal incorporation into intracellular soluble protein. 

The following method has been applied to aniline, ortho- and paratoluidine, metaxylidine, and sulphanilic acid. A known quantity of the base is diazotized and made up to a certain volume it is then immediately added from a burette to a solution of Schafer s salt, ... 

Diazo methods Many laboratories estimate bilirubin by its reaction with diazotized sulphanilic acid to form azobilirubin (the Van den Bergh reaction). Conjugated bilirubin reacts rapidly and is therefore sometimes referred to as direct-acting bilirubin. On the other hand, unconjugated bilirubin will only react if an accelerating agent is present and this is referred to as the indirect reaction. 

As well as diazotized sulphanilic acid, other diazo reagents have been tried, e.g. 2,4-dichloroaniline. 

A commonly used method for the estimation of total and conjugated bilirubin in serum. It is based on the diazotization of bilirubin by diazotized sulphanilic acid to azobilirubin which is coloured blue in alkaline solutions. Caffeine-sodium benzoate is... 

The reaction of bilirubin with diazotized sulphanilic acid to form azobilirubin. It is widely used for the estimation of bilirubin. 

Coupling with diazotized sulphanilic acid has also been used as the basis of a method for determining phenolic antioxidants in polyethylene. ... 

The hydroxylamine is oxidized to nitrite with an acidic iodine solution and the excess iodine destroyed by arsenite. The nitrite thus produced is determined by diazotizing sulphanilic acid and coupling with N-( 1-naphthyl)-ethylenediamine to form a highly coloured azo dye, the extinction of which is measured. A correction is made for any nitrite initially present in the sample. 

Diazo coupling—Under conditions where 2-picoline failed to react with diazotized sulphanilic acid or / -aminobenzoic acid, diazotized / -nitroaniline gave 7 per cent of pyridine-2-aldehyde j -nitrophenylhydrazone2i3. In acetic acid containing sodium acetate, the yield i s 58 per cent. Pyridyl-2-acetic acid and its homologues take part efficiently in the Japp-Klingemann... 

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