CS228469B1 - Process for preparing azo dye - Google Patents

Abstract

The purpose of the invention was to increase the yield of the coupling in the production of 2-cyano-4-nitro-4'-[(N-methoxycarbonylethyl-N-cyano-ethyl)-amino]-1,Γ- -azobenzene. The purpose was achieved by conducting the reaction in such a way that N-methoxycarbonylethyl-N-cyanoethylaniline is admitted to an aqueous charge of a diazonium salt prepared by diazotization of 2-cyano-4-nitroaniline with nitrosylsulfuric acid, the feed of which initially precedes, but ends simultaneously with or remains slightly delayed after the feed of the passive component.

Description

The present invention relates to a process for the preparation of 2-cyano-4-nitro-4 ‘- [(N-methoxycarbonylethyl-N-cyanethyl) amino] -1,1--azobenzene of the formula

C _i h _{i il} COOCH

C 2 CN coupling of 2-cyano-4-nitrobenzenediazonium sulfate with N-methoxycarbonylethyl-N-cyanethylaniline, which, after final dispersion grinding, serves as a commercial dye.

To date, the present dye is prepared by allowing a solution of the diazonium salt, prepared by diazotizing 2-cyano-4-nitroaniline with nitrosylsulphuric acid dissolved in concentrated sulfuric acid, to flow onto the ice and allowing the resulting aqueous diazonium salt solution to be allowed at 0-5. ° C slowly N-methoxycarbonylethyl-N-cyanethylaniline.

A disadvantage of this process is the low yield of the dye produced by the coupling, due to the 2-cyano-4-nitroaniline diazonium salt decomposing relatively rapidly in the aqueous medium even at low temperature.

It has now been found that this deficiency removes the process for preparing the 2-cyano-4-nitro-4 '- [; (N-methoxycarbonylethyl-N-cyanethyl) -amino] -1,1'-azobenzene azo dye by coupling 2-cyano-4-nitrobenzenediazonium sulfate with N-methoxycarbonylethyl-N-cyanethylaniline, according to the invention, characterized in that the coupling is carried out by admixing either the crude product of the passive component or the pure distilled product prepared according to AO No. 186 950 dissolved in acetic or hydrochloric acid into an aqueous diazonium salt Preferably, the passive component can be added to the master aqueous solution of the active component with ice so that the acidity of the coupling medium does not drop to pH 2, the temperature of the aqueous diazonium salt solution at admitting the concentrated diazotizing mixture into the template and maintain during the coupling U is -18 to ^0-0 ° C and diazotised slurry inflow active components in concentrated sulfuric acid at ice present does not exceed 10 minutes.

The advantages of the process according to the invention are higher coupling yields since the diazonium salt of 2-cyano-4-nitroaniline is fairly stable in concentrated sulfuric acid. Separate dissolution of the weakly basic passive component in hydrochloric acid prior to coupling, or in the case of poor solubility of the crude product of the passive component dissolved in acetic acid, is appropriate for good performance.

Example 1

To 230 g of concentrated sulfuric acid is added 14 g of anhydrous, finely divided sodium nitrite, optionally warming to 65-70 ° C until complete dissolution. The resulting nitrosylsulphuric acid is cooled to 0-5 ° C, to which 32.6 g of 2-cyano-4-nitroaniline is finely ground and mixed thoroughly with 3% sodium bicarbonate over a period of 1/2 to 1 hour so that the temperature does not rise. ^C 10 C, stirred for 2 hours, the drop of sample is dissolved in a small amount of ice water without residue.

The diazotizing mixture of 2-cyano-4-nitroaniline is allowed to admix as quickly as possible with good stirring to a sample of 800 g of ice so that the temperature does not exceed 0 ° C. Simultaneously with a small delay, as soon as 10-25% of the total amount of the concentrated diazotization mixture is in the receiver, an ice solution of the passive component prepared from the crude or distilled product prepared according to AO No 186 950 is admitted in an amount corresponding to 46.4 g N - (n-methoxycarbonylethyl) -N- (n-cyanethyl) -aniline, by dissolving in 100 g of ice from 80 g of 32% hydrochloric acid, this is done so that the passive component is already present in the draft before the last part is fed At -15 ° C to 0 ° C, the coupling is generally complete within 1-2 hours, after dilution with water to 2500-3000 ml, filtered and washed with water until neutral. dyes.

Example 2

46.4 g of (N- (N-methoxycarbonylethyl) -N- (n-cyanethyl) aniline are dissolved in 168 g of acetic acid. This solution is added to an ice pack with the active component, coupled and further processed as in Example 1 .

Claims (4)

I will invent the object A process for the preparation of a 2-cyano-4-nitro-4 '- [(N-methoxycarbonylethyl-N-cyanethyl) -amino] -Ι, Γ-azobenzene _azo dye of the formula _WO 00CH ₃ N by coupling 2-cyano-4-nitrobenzenediazonium sulfate with N -methoxycarbonylethyl-N-cyanethylaniline, characterized in that the coupling is carried out by admitting a crude passive component, optionally pure distilled dissolved in acetic or hydrochloric acid, to an aqueous diazonium salt of the active component, the feed of which initially precedes but ends or remains slightly delayed after the inflow of the passive component. 2. A process for the preparation of an azo dye according to claim 1, characterized in that the passive component is poured into an aqueous solution of the active component with ice so that the acidity of the coupling medium does not drop above pH 2. 3. A process for the preparation of an azo dye according to claim 1, wherein the temperature of the aqueous diazotium salt solution is maintained at -18 to 0 [deg.] C. while allowing the concentrated diazotization mixture to the master and during the coupling. 4. A process for preparing an azo dye according to claim 1, wherein the feed of the diazotizing mixture of the active component in concentrated sulfuric acid to the present ice does not exceed 10 minutes.