DE512820C - Process for the preparation of oxyanthraquinone derivatives, in particular alizarin and its derivatives - Google Patents

Description

Process for the preparation of oxyanthraquinone derivatives, in particular Alizarin and its derivatives The invention relates to a process for the preparation of oxyanthraquinone derivatives, in particular alizarin and its derivatives.

It is known to use oxyanthraquinone derivatives, e.g. B. Alizarin, by the Action of alkalis on both sulfonic acids, e.g. B. Anthraquinone-ß-sulfonic acid, and halogen derivatives of anthraquinone, e.g. B. PP-chloranthraquinone, as well To produce 2-oxyanthraquinone and 2-aminoanthraquinone.

It is also known that anthraquinone-2-carboxylic acid in the alkali melt converted into an oxyanthraquinone derivative, the x-Ox "-2-anthraquinone carboxylic acid will.

You also have 2-alkylanthraquinones with alcoholic potassium hydroxide solution, optionally with the addition of oxidizing agents, heated without the formation has been observed by alizarin; rather, a condensation product was obtained of the P-substituted anthraquinone.

It has now surprisingly been found that when anthraquinone derivatives are heated, the P-position carbon-containing groups, whose carbon atom directly bound to the anthraquinone ring in an aqueous solution of caustic alkali, optionally in the presence of an oxidizing agent, especially oxyanthraquinones Alizarin, receives. The reaction is expediently carried out in an autoclave at 18o ' carried out. Has compared to the well-known process of producing alizarin So this has the great advantage that it is carried out in aqueous solution, whereby overheating can be avoided more easily than with melting reactions.

With the invention it has become possible to use alizarin and other oxyantraquinones from very cheap intermediate products, especially from 2-methylanthraquinone, produce, which in turn easily in excellent purity from toluene and Phthalic anhydride can be obtained according to a variant of the Friedel-Crafts synthesis can.

The invention is explained below using a few exemplary embodiments. Parts mean parts by weight. Example r zg parts of anthraquinone-t3-carboxylic acid in z 25o parts caustic soda solution, the 25o parts caustic soda and 6 parts sodium chlorate contains, dissolved. The mixture is then placed in an autoclave and under good stirring for 24 hours heated to 18o '. The melt can then be used in a known Be worked up in a way, for example by pouring into water and acidifying, or you leave them Cool the melt and then filter the Alkali salt of alizarin, which is then crystallized, through a suitable filter, for example Monel metal cloth. In this case the filtrates contain the excess Alkali. They can then be used for further melts. The alizarin press cake is then processed in the usual way on Allzarin. Example 2 6o parts ß-methylanthraquinone, 252 parts caustic soda, = q. Parts of sodium chlorate and ggo parts Water are mixed together and placed in an autoclave with stirring for 24 hours heated for a long time at = 80 ° C. The melt is then allowed to cool, the deposited The sodium salt of alizarin is filtered off from the mother liquor. The alizarin salt is dissolved in boiling water, whereupon unchanged 2-methylanthraquinone is filtered off will. The free allzarin is precipitated from the filtrate by acidification.

The after the removal of the alkali salt of the alizarin from the cooled Caustic soda lye that remains in the melt can reappear in the subsequent melts Find use.

The proportions of anthraquinone derivatives given in the examples, Oxidizers, caustic alkalis, and water can be changed considerably.

Claims (2)

PATENT CLAIMS: i. Process for the preparation of oxyantlirachinone derivatives, in particular allzarin and its derivatives, characterized in that anthraquinone derivatives, the ß-position carbon-containing groups contain their carbon atom directly attached to the anthraquinone ring, such as 2-alkyl-, 2-carboxyanthraquinones; possibly in the presence of an oxidizing agent, the action of an aqueous solution of Subject to caustic alkali at elevated temperature under pressure. 2. The method according to claim i, characterized in that the temperature of the reaction mixture to approximately = 8o ° C is kept.