Investigation in a Series of Pyrazolone Monoazo Dyes

L. P. Kulev, G. M. Stepanova

Pyrazolone azo dyes, as is known, are distinguished by great brightness of shade and find wide application in dyeing practice.

The literature describes a large number of azo dyes derived from pyrazolone, in which 4-aminoantipyrine serves as the diazo component.

For the purpose of studying physiological activity, we synthesized 2-, 3-, and 4-aminobenzoylaminoantipyrines, not previously described in the literature [1]. It was also of interest to test these compounds as diazo components for obtaining azo dyes, since acyl derivatives of aminoantipyrine, as our experiments have shown, are obtained with some difficulty. Consequently, the presence of an acylamino group cannot fail to have an effect on the strength of the dyes.

The monoazo dyes were synthesized by coupling diazotized 2-, 3-, and 4-aminobenzoylaminoantipyrines with azo components according to the scheme:

\[ \begin{array}{c} \begin{array}{c} \mathrm{H_3C{-}C{=}C{-}NH{-}CO{-}Az{-}N{\equiv}N} \\ \quad\ \,| \qquad\quad | \\ \mathrm{H_3C{-}N} \qquad \mathrm{C{=}O} \\ \quad\ \backslash \quad / \\ \mathrm{N} \\ | \\ \mathrm{C_6H_5} \end{array} \ \mathrm{Cl} \ +\ \mathrm{H{-}R} \ \longrightarrow\ \begin{array}{c} \mathrm{H_3C{-}C{=}C{-}NH{-}CO{-}Az{-}N{=}N{-}R} \\ \quad\ \,| \qquad\quad | \\ \mathrm{H_3C{-}N} \qquad \mathrm{C{=}O} \\ \quad\ \backslash \quad / \\ \mathrm{N} \\ | \\ \mathrm{C_6H_5} \end{array} \ +\ \mathrm{HCl} \end{array} \]

To prepare the solution of the diazo component, acylaminobenzoylaminoantipyrine in the form of the hydrochloride was dissolved in water. To the solution was added the calculated amount of hydrochloric acid. The solution was cooled with ice to \(0\text{--}5^\circ\mathrm{C}\), and, with stirring, a solution of sodium nitrite was added dropwise. The end of diazotization was determined by a spot test with diazotized 4-nitroaniline. The azo component was dissolved in water in the cold or with heating in the presence of acid, soda, or alkali, depending on the nature of the azo component [2].

Coupling was carried out with cooling and mechanical stirring. During the coupling process, the reaction mixture was tested for the presence of diazo compound (spot test with an alkaline solution of R salt) and of azo component (spot test with diazotized 4-nitroaniline).

After completion of coupling, the precipitate was filtered off, washed with water, and dried. Further purification of the dye was carried out by treating it with boiling alcohol.

In view of the fact that the synthesized dyes are insoluble in water, the dyeings were obtained by coupling the azo and diazo components directly on the fiber. The fastness of the dyeings to wet treatments was determined by standard methods [3].

The characteristics of some of the dyes obtained by us are given in the table.

TABLE

As is evident from the table, the properties of the dyes obtained depend to a considerable extent on the position of the amino group in the benzene ring of the acyl residue of the diazo component.

Thus, diazotized 4-aminobenzoylaminoantipyrine gives, with all azo components, deeper shades than the other two isomers.

A comparison of the shades obtained by combining diazotized 4-aminoantipyrine and 4-aminobenzoylaminoantipyrine with the same azo components showed that the presence in the molecule of the dyes synthesized by us of the acylamino group does not noticeably affect the color of these dyes. However, the presence of this group has a substantial effect on the fastness of the shades to wet treatments. The dyes described here are insoluble in water, as a result of which the fastness of their shades to wet treatments is much higher than that of analogous derivatives of 4-aminoantipyrine.

Conclusions

1. Forty-two monoazo dyes, not described in the literature, derivatives of 2-, 3-, and 4-aminobenzoylaminoantipyrines, have been synthesized.

2. It has been found that the position of the substituents in the benzene ring of the acyl residue of the diazo component influences the color of the dye; the deepest shades are given by dyes with the substituent in the para position.

1. It has been established that monoazo dyes derived from acylaminoanthipyrines give colors that are considerably more resistant to wet treatments than monoazo dyes based on 4-aminoantipyrine.

REFERENCES

1. G. M. Stepanova, Dissertation, Tomsk, 72, 1955.
2. M. A. Chekalin, F. F. Eremin, Production of Azo Dyes, 417, 1952.
3. Methods for Testing the Fastness of Dyes, GOST 5751—51, group L-29.