AT64815B - Process for the preparation of quinizarin. - Google Patents

Description

  

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  Process for the preparation of quinizarin.



   Through the work of Grimm (Ber., 6 [1873], p. 506/8) and Bayer and Caro (Ber., 7 [1874], p. 973) a synthesis of quinizarine by heating phthalic anhydride and hydroquinone with concentrated Sulfuric acid became known. The latter authors then found that the hydroquinone can also be replaced by p-chlorophenol, but here quinizarine is only formed as the main product at higher temperatures, while under moderate conditions (cf. also Ber., 8 [1875], p. 152 ) usually dichloromurane is formed. Liebermann (Ann., 212 [18821, p. 10/12) worked out the method of representation given last, but states that he was only able to obtain 5% crude quinizarine containing purple.



   It has now been found that this synthesis, which is unusable for technology, becomes a technically extremely valuable one if it is carried out in the presence of boric acid.



   The effect of boric acid is first of all a condensing one, because under certain conditions.
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   Sulfuric acid and at lower temperatures), considerable amounts of quinizarin are formed in the presence of boric acid. The protective effect of boric acid, known from the literature (cf. e.g. D. R. P. No. 81481) when hydroxyl groups are introduced into anthrachillone derivatives, undoubtedly also comes into play here, but this effect is only secondary here.



   However, from DRP No. 134985 (see also Ber, 36 [1903J, p. 557), the beneficial influence of boric acid in the synthesis of oxynaphtazenchinone has become known, in that the yield due to the addition mentioned is 30% of theory (see Ber . ibid., 1903], p. 550). while the reaction product is partly sulfated and partly further changed.



   In the present representation of quinizarin from p-chlorophenol, the addition of boric acid now increases the yield from about 4% to 75% of theory. The method is carried out by heating the components with boric acid-containing sulfuric acid, the concentration of the sulfuric acid and its boric acid content in
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   Example 1: 80 parts of phthalic anhydride are added to 400 parts of sulfuric acid (96th).



    Entered 20 parts of boric acid and 23 parts of p-chlorophenol. The mixture is heated to 150 for three hours, then the temperature is increased to 180 to 2000 and held at this temperature for as long. until the quinizarin content. recognizable by the increasing color of the melt, it no longer increases.



  Working up is carried out by pouring the cooled melt into 20 parts of water. A hfiltrien'l1, boil with plenty of water and dry. The yield is 70 to 80 ",) of theory.



     Example 2: 200 parts of 20% oleum are mixed with 60 parts of p-chlorophenol and the melt is kept at 130 to 1400 for as long. until a sample of the melt in 120 iger saline solution no longer shows any separation. The p-chlorophenol disulfonic acid is then retained in the melt. Without dissolving the disulfonic acid, 200 parts of 96% strength sulfuric acid are used. 40 parts of boric acid and 80 parts of phthalic anhydride and heated as indicated in Example 1.
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 Untreated asbestos, washes with sulfuric acid from 60 Bé and ice water and dries.

   By boiling this body with water or sodium carbonate solution, quinizarin is obtained in excellent purity.
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 the examples 1 and 2 indicated, heated, the yield is the same as when using the Üqmmolecular amount of p-chlorophenol.

** WARNING ** End of DESC field may overlap beginning of CLMS **.

 

Claims (1)

PATENT CLAIM: Process for the preparation of quinizarin by condensation of p-chlorophenol or its sulphonic acids and phthalic anhydride with concentrated or fuming sulfuric acid, characterized by the addition of boric acid to the sulfuric acid melt. ** WARNING ** End of CLMS field may overlap beginning of DESC **.