Phenols reaction with 4-aminoantipyrine

Phenols Reaction with 4-aminoantipyrine at pH 10 in the presence of potassium ferricyanide, forming an antipyrine dye that is extracted into pyridine and measured at 460 nm... 

Before an immobilized enzyme can be used for an industrial process, it is essential to characterize it in terms of its catalytic and kinetic properties. A quantitative assay must be developed to measure the activity, kinetic parameters, and stability of the enzyme. In a coupling reaction, H202 rapidly reacts with phenol and 4-aminoantipyrine (electron donor) in the presence of peroxidase to produce a quinoneimine chromogen (Equation E12.2, Figure El 1.2), which is intensely colored with a maximum absorbance at 510 nm. (This is the same as the product formed in the analysis of cholesterol in Experiment 11.)... 

Chlorine dioxide and hypochlorite have also been determined simultaneously in aqueous samples by high-performance liquid chromatography. The analytes are first separated on an anion-exchange column. After separation, a postcolumn reaction with 4-aminoantipyrine (5), and phenol is carried out, forming a chromogenic substance that absorbs at 503 nm through an oxidation-condensation reaction. 

Phenols react with 4-aminoantipyrine to give in-dophenols in the presence of hydrogen peroxide and peroxidase under weak alkaline conditions. The resultant indophenols are determined by absorptiometry. Potassium hexacynoferrate (III) can also be used as an oxidant. As the indophenols have electrochemical activity, this reaction is utilized for precolumn derivatization for LC-ECD. 

When oxidized by iron(III) ions 4-aminoantipyrine reacts with phenols to yield colored quinonoid derivatives (cf. 4-aminoantipyrine — potassium hexacyanoferrate(III) reagent in Volume 1 a). It is an oxidative coupling based on the Emerson reaction. 

Phenolic compounds in aqueous and solid samples may be estimated as total phenols by colorimetric analysis. The method involves the reactions of phenols with 4-aminoantipyrine in the presence of potassium ferricyanide at pH 8 to form a yellow antipyrine dye (soluble in chloroform), the absorbance of which is measured by a spectrophotometer at 500 nm. 

Phenol-type substances, and also certain other compounds capable of coupling react with 4-aminoantipyrine, to produce - in alkaline reaction... 

The determination of traces of phenolic species has been successfully accomplished by adaptation of batch standard methods based on the oxidative coupling of the analytes with 4-aminoantipyrine. The online preconcentration of the reaction products using solvent extraction, sorption/elution, or sorbent extraction-based optosensing techniques rendered detection limits below the maximum level recommended by EPA Directives. Interferences caused by colored aromatic amines can be successfully circumvented by analyte enrichment on reversed-phase materials prior to their oxidative coupling. 

The absorbance of the red quinonamine dye formed in the reaction of phenol and 4-amino-l,5-dimethyl-2-phenyl-3-pyrazolone (4-aminoantipyrine) with periodate ions has been used in the estimation of periodate consumption in the oxidation of starch and other carbohydrates. The evaluation of the use of pyridine as a solvent in the oxidation of water-insoluble carbohydrates by periodate has been reported. The three types of dialdehydes produced by this oxidation were converted to the TMS ethers of the dithioacetals and measured by g.l.c. Oxidation proceeded in a normal Malapradian fashion but more slowly than it does in water. 

In these cases it is usually possible to explain why the color is formed. The reactions can be further classified, on the basis of the type of colored compound formed, into reactions leading to the formation of azo dyes, di- or triphenylmethane dyes, xanthene dyes, polymethine dyes, indophenols, etc. Azo dyes are formed, for example, in the reaction of diazonium salts and phenols (p. 192) or amines (p. 324), azomethines in the reaction of primary aromatic amines with aromatic aldehydes (p. 215), di- and triphenylmethane dyes in the reaction of aromatic aldehydes with aromatic hydrocarbons in concentrated sulfuric acid (p. 213), triphenylmethane dyes in the reaction of phenols with aromatic aldehydes or oxalic acid (p. 196), xanthene dyes in the reaction of anhydrides of dicarboxylic acids with resorcinol (p. 196), polymethine dyes are formed after the cleavage of the pyridine ring in the reaction of the glutaconaldehyde formed and barbituric acid (p. 378), indophenols on reaction of phenols with Gibbs reagent (p. 195), or 4-aminoantipyrine according to Emerson (p. 194), or on the Liebermann reaction (p. 195). 

---