DE1568291A1 - Process for the preparation of 1,2-dihydroxy cyclobutenedione - Google Patents

Description

Process for the preparation of 1,2-dihydroxy - cyclobutenedione It is from J, Amer. Chem. Soc. 81, 3480 (1959) known, 1,2-dikydroxy - cyclobutenedione - also called "squaric acid" - to be produced in the following way: Monochlorotrifluoroethylene is dechlorinated to perfluorocyclobutene with dimerization. You put this with Alcoholate to 1,2-dialkoxy-tetrafluocyclobutene, in the hydrolysis of which then the Squaric acid results. According to another, from Angew. Chem. 75, 982 (1963) Process is first hexachlorobutadiene with ethylate to 1-ethoxypentachlorobutadiene (1,3) implemented. This can be thermally catalytically cyclized to the perchlorocyclobutenone, from which the squaric acid can then be obtained by hydrolysis.

These known manufacturing processes are quite expensive because the Products of the individual process stages are isolated and processed separately Need to become.

The process according to the invention is based on the task of 1,2-dihydroxyclobutendio from hexachlorobutadiene in a one-pot process.

According to the invention, this object is achieved by using hexachlorobutadiene heated with excess morpholine, dilute the resulting reaction mixture with aqueous acids to a p11 value of 5 to 9, it is ßrongt at temperatures Stirring from 0 to 100 ° C, the resulting mixture is then strongly acidified and, for siding heated, The process according to the invention is based on the following reaction sequence based on: from hexachlorobutadiene and morpholine, trichloro-trimorpholino-butadiene is formed, that in an aqueous medium within the pH range c 5 to 9 in ß-morpholino-trichlorocyclobutenone transforms. This produces 1,2-dihydroxy-cyclobutenedione by acid hydrolysis.

The hexachlorobutadiene used as the starting product falls as undesirable, very unreactive by-product in large quantities in high-temperature chlorination of hydrocarbons.

To carry out the process according to the invention, hexachlorobutadiene is first used with a large molar excess of morpholine, preferably 8 to 12 times molar amount, heated to temperatures of 60 to 100 ° C for a few hours. That the resulting basic reaction mixture is treated with dilute aqueous acids, z. 13. Hydrochloric acid, sulfuric acid or acetic acid "» brought to the desired pH value, the pH range from 6 to 8 being preferred. One stirs the resulting aqueous mixture for several hours at a temperature of 20 to 100 ° C, preferably from 50 to 75'C, and then acidified with mineral acids, preferably hydrochloric acid or Heavy rock, strong on.

This acidic reaction mixture will eventually last for several hours heated to boiling; 1,2-dihydroxy-cyclobutenedione crystallizes on cooling and can be filtered off. - The present in the filtrate morpholine can after conventional procedures can be recovered and used again.

The volume of the batch and the acid consumption can be small keep that the excess morpholine immediately after the implementation of the Hexachlorobutadiene with morphoiln, i.e. before a pH value is set in the area vo @@@@@@@ @@@@@@ completely or partially distilled off. Further recommends it is acidic, before the strong acidification, the water present in the reaction mixture and to evaporate at least part of the morpholine. It has also proven beneficial proven the heat treatment in the pH range from 5 to 9 thereby to interrupt that the reaction mixture is acidified and after a short time with Morpholine returns to the starting pH. With this short-term change in pH value namely, the precipitate which has precipitated out goes into solution to the Tcil; and that dissolves the starting product of this reaction phase - trichloro-trimorpholino-butaiden - while that the end product - ß-morpholino-tric hlorcyc lobutenone - remains undissolved, In this way, the starting product is made from a reaction-inhibiting coating freed.

It is surprising that in the process according to the invention, the Vicl number of the by-products obtained in the individual reaction processes, the process of the Overall reaction hardly started.

1,2-Dihydroxy-cyclobutenedione serves as a valuable intermediate for the production of antioxidants, also for the production of bactericides, Fungicides and insecticides.

Example To 174.2 g (2 mol) of morpholine are added at one temperature from 97 ° C within half an hour under 65.2 g (0.25 mol) of hexachlorobutadiene added dropwise with good stirring. The mixture is then stirred at this temperature for a further 3 hours long after. After standing for 12 hours at room temperature, the batch is charged with 20 % hydrochloric acid adjusted to pH 7.0 and stirred at 55 ° C. To The reaction mixture is acidified for 1 1/2 hours with 20 ccm of 20 hydrochloric acid, after 10 minutes with morpholine brought back to the p-value of 7.0 and more Stirred for 2 hours at 55 ° C. Then the approach in the vacuum is narrowed as much as possible and refluxed for G hours with 200 cc of concentrated hydrochloric acid. That Solid product which crystallizes out on cooling is filtered off and recrystallized from water. This gives 11.3 g (39.7% of theory, based on the hexachlorobutadiene used) 1,2 dihydroxy cyclobutenedione with a decomposition point of 275 to 300 ° C.

Claims (1)

Claim process for the production of 1,2-dihydrox5- cyclobutcndione, characterized in that hexachlorobutadiene is heated with excess morpholine, the resulting reaction mixture is adjusted to a pH value with dilute aqueous acids from 5 to 9, it is stirred at temperatures of 20 to 100 ° C, the resulting The mixture is then strongly acidified and heated to the boil.