CS243592B1 - Method of evidence and identification, 2-hydroxy-6-pyridone grouping in azo dyes - Google Patents

Abstract

A rapid method for the detection and identification of the 2-hydroxy-B-pyridone group in azo dyes by dissolving the dye sample in diluted ammonia, optionally with the addition of dimethylformamide, and reducing it with zinc in an aqueous ammonia with resorcinol environment, and transferring the mixture thus obtained to filter paper to form a blue coloration. Alternatively, the reaction mixture is chromatographed in a 1-propanol-water system in a 2:1 ratio, and the hue and Rf value are compared with the standard.

Description

(54) Method of identification and identification of the 2-hydroxy-6-pyridone moiety in azo dyes

2

A quick way to identify and identify the 2-hydroxy-β-pyridone moiety in azo dyes by dissolving the dye sample in dilute ammonia, optionally with dimethylformamide, and reducing it with zinc in aqueous ammonia with resorcinol and transferring the mixture to filter paper to form blue coloration, optionally said reaction mixture is chromatographed in a system of 1-propanol-water in a ratio of 2: 1 compared with the hue and R _f -value with the standard.

The invention relates to a method for the identification and identification of a 2-hydroxy-6-pyridone moiety in azo dyes. Azo dyes of the general formula

where

R 1 -alkyl of 1 to 8 carbon atoms,

R ₂ - CN, -CONH, - CH2SO3H, -H,

R3 = —CH3, —COOH,

R 4 = phenyl, naphthyl, optionally further substituted, heterocyclic radical containing N, S, O heteroatoms are desirable dyes for coloring synthetic materials, predominantly greenish-yellow. Their analytical determination has not yet been described in the literature. It is known to react other heterocyclic components from azo dyes, such as pyrazolones, which give an indophenol reaction to form a red to violet colored oxidation product.

It has now been found that the dyes of the above formula provide an intensely blue colored filter paper infusion after reduction with zinc powder in aqueous ammonia with resorcinol. The resulting coloration is sufficiently stable and is characteristic of the 2-hydroxy-6-pyridone moiety. The development of the blue-colored product follows the scheme:

^CH 3

The method can be further extended to identify fragments with a pyridine moiety.

According to the invention, a method for the identification and identification of the 2-hydroxy-6-pyridone moiety in the azo dyes mentioned above is to dissolve the dye sample in dilute ammonia, optionally with dimethylformamide, and reduce it with zinc in aqueous ammonia with resorcinol. on filter paper to cause a blue colouration, optionally said reaction mixture is chromatographed on paper in a system of 1-propanol-water in a ratio of 2: 1 compared with the hue and R _r value standard.

The results of paper chromatography of color products are compiled in the following table:

Table

Passive component of azopyridone dye

2-hydroxy-4-methyl-6-pyridone

2-hydroxy-1,4-dimethyl-6-pyridone

2-hydroxy-1,4-dimethyl-5-cyano-6-pyridone 1-ethyl-2-hydroxy-4-methyl-5-cyano-6-pyridone 1-butyl-2-hydroxy-4-methyl-5- cyan-6-pyridone

1- (2'-ethylhexyl) -2-hydroxy-4-methyl-5-cyano-6-pyridone

2-hydroxy-4-methyl-5-carboxy-6-pyridone 2-hydroxy-1,4-dimethyl-5-carbamoyl-6-pyridone 1-ethyl-2-hydroxy-4-methyl-5-carbamoyl-6- pyridone

1- (1'-ethylene-4'-sulfobenzene) -2-hydroxy-4-methyl-5-carbamoyl-6-pyridone

Rf Color stains

0.32 blue violet 0.35 blue violet 0.49 blue violet 0.67 blue violet 0.88 blue violet 0.90 blue violet 0.50 blue violet 0.39 dark blue 0.58 dark blue 0.35 dark blue

From the tabulated results show that the color shade of blue spots in the chromatogram is affected by the 5-substituent (-CN: bluish violet, -CONHSO: dark-blue, - CH2SO3H: light-blue], R _f -value is particularly affected by the alkyl chain length to pyridone nitrogen atom.

The examples below illustrate the method of proof and identification of the invention.

Example 1 mg of the dye (with solubilizing group) is dissolved in 1 ml of ammonium hydroxide (1: 1) and reduced by adding 1 g of zinc powder. After the reaction mixture had decoloured, 50 mg of resorcinol was added and the blue color of the infusion on filter paper was positive evidence of the pyridone moiety in the dyes.

Example 2

To identify the pyridone moiety of the molecule, apply by micropipette at the start of the chromatogram (Whatman paper # 3) 5 μΐ of the reaction mixture (Example 1) together with a series of authentic substances prepared by the same procedure from azo dyes of known constitution. 1-propanol-water (2: 1). Comparison of the blue indophenol spots is carried out according to the position of the spot in the chromatogram (Rf _- value) and its shade.

EXAMPLE 3 mg of a solubilizing group-free dye is dissolved in 1 ml of dimethylformamide with the addition of 5 drops of dilute ammonia (1: 1) and reduced with 1 g of zinc powder. A blue infusion of paper indicates the presence of the hydroxypyridone portion of the dye molecule.

Example 4

Identification of the pyridone moiety is carried out analogously to Example 2.

Claims (1)

Subject Method for the identification and identification of a 2-hydroxy-6-pyridone moiety in azo dyes, characterized in that the dye sample is dissolved in dilute ammonia, optionally with the addition of dimethylformamide and reduced by zinc in aqueous ammonia with resorcin. Alternatively, the reaction mixture is chromatographed on paper in a 1: propanol / water 2: 1 ratio and the shade is compared with the _Rf value against the standard.