DE1093791B - Process for the separation of pure ª † -isomers from isomer mixtures of hexachlorocyclohexane - Google Patents

Description

Process for the separation of pure γ-isomers from isomer mixtures des hexachlorocyclohexane From that obtainable by the addition of chlorine to benzene Hexachlorocyclohexane comes in handy for use as an insecticidal agent only the y-isomer is considered, which is in the reaction product of the benzene chlorination (Raw hexachlorocyclohexane) to 12 to 1801o in addition to the a-, ß-, d-, E-isomers as well contains other chlorination products.

The invention relates to a new process for the separation of pure y-isomers from isomer mixtures of hexachlorocyclohexane, in particular from Mixtures of isomers that result in the work-up of the crude hexachlorocyclohexane, e.g. B. from mother liquor residues, and at least 25% y-isomer and besides higher chlorinated products mainly a- and d-hexachlorocyclohexane, at least but contain 30 ° / 0 d-isomer.

A number of methods have become known that serve this purpose serve to isolate the pure y-isomer from hexachlorocyclohexane concentrates.

It is known that from isomer mixtures of hexachlorocyclohexane by single or repeated extraction with paraffinic hydrocarbons des Boiling range from 65 to 2000 C and subsequent cooling of the extracts hexachlorocyclohexane concentrates with a y-isomer content of 60 to 70 ° / 0 are crystallized out by Recrystallization from paraffin hydrocarbons enriched to 80 to 950 /, y content can be. As is further known, hexachlorocyclohexane can have a high content of y isomers from isomer mixtures with about 400 /, y content are obtained by the other isomers and impurities in one operation with a mixture dissolves out of dioxane and gasoline.

A t000 / 0 γ-hexachlorocyclohexane can by known methods by one-time recrystallization of a 9001, proprietary technical y-hexachlorocyclohexane are obtained, which in turn is obtained by hot extraction with a lower alcohol from a mixture of isomers one of a-, ß- and y-isomers saturated solution of the undissolved matter containing no or less than 20% d-isomer separated and rapidly cooled to temperatures at which the 7, -isomer crystallizes out, however, no significant separation of a- and fl-isomers takes place and the γ-isomer which has crystallized out is separated off immediately. This procedure can only be carried out if the starting isomer mixture subjected to the hot extraction has no or only Contains small amounts of d-isomers, the weight fraction of which is far below 20% amounts to.

Another method is to use the crude hexachlorocyclohexane Methanol extracted at room temperature, the extract of which remained undissolved a- and ß-isomers separated, the methanolic filtrate largely by evaporation narrowed and the received Suspension of precipitated crystals, which also a- and fl-isomer contain, at temperatures above 65 "C, preferably at 70 to 150 "C, heated under pressure until the crystals completely dissolve. The γ-isomer is left from the solution which is supersaturated in α- and β-hexachlorocyclohexane crystallize out and separates the crystals from, whereby a 90- to 950 /, ges y-hexachlorocyclohexane is won. In this process, too, it only succeeds after recrystallization from methanol in the same procedure to obtain a 100% pure γ-isomer. In addition, the pressure treatment required by the process requires a special one equipment expenditure.

According to a well-known, cycle-based process, this is Starting isomer mixture with a small part of that from previous cycles originating mother liquor is first subjected to a pre-extraction and the obtained Pre-extract, which contains the same amounts of d-isomer as that for the extraction coming starting mixture, withdrawn from the cycle and discarded. Then will the pre-extracted isomer mixture with the remaining parts of the mother liquor, with the washing liquids and with the mother liquors of the recrystallization as well if necessary re-extracted with fresh solvent. From this main extract, which is concentrated by evaporation, while its content of <3 isomer 5 to 15 ° / 0, γ-hexachlorocyclohexane for crystallization. From the received y-isomers with about 97.50 /, y-content can be obtained by recrystallization of y-hexachlorocyclohexane can be obtained in a purity of 99.8 01o.

It is also known that the pure y-isomer of hexachlorocyclohexane to win by a concentrate enriched with the y-isomer by means of a saturated Solution of the y-isomer, e.g. B. in dioxane extracted is, with all other isomers as well as the more chlorinated products in solution go and the undissolved y-isomer remains. A practical implementation of this The process requires that in the starting isomer mixture subjected to the extraction the proportion of y-isomer is about 40 to 600%.

Pure γ-hexachlorocyclohexane can be prepared by a known method also from hexachlorocyclohexane isomer mixtures, the more than 40 ° / 0 y isomer besides mainly containing a-isomer, are obtained by heating these mixtures with dioxane, deposition of a γ-hexachlorocyclohexane-dioxane molecular compound Cooling, separation of the molecular compound from the mother liquor and decomposition of the separated molecular compound into its constituent parts.

Finally, there is a method for making pure γ-hexachlorocyclohexane from hexachlorocyclohexane isomer mixtures with a predominant amount of γ-hexachlorocyclohexane known in addition to α-hexachlorocyclohexane, the isomer mixture of carbonic acid dimethyl ester recrystallized and the resulting molecular compound from γ-hexachlorocyclohexane and dimethyl carbonate is cleaved by heating.

So much for the isolation of the pure y-isomer via the intermediate Production of molecular compounds from γ-hexachlorocyclohexane and dioxane or from y-hexachlorocyclohexane and dimethyl carbonate are provided according to the mentioned process starting mixtures with a content of y-isomers in the amount of 40 to 80 ° / 0 assumed.

The task of separating off pure γ-isomers therefore remains of hexachlorocyclohexane from isomer mixtures which have a considerably lower Have content of y-hexachlorocyclohexane and considerable amounts of d-isomer may contain, both the application of pressure and the repeated recrystallization of highly concentrated products is avoided.

The invention is based on the new knowledge that from one to Boiling temperature heated solution of γ-hexachlorocyclohexane and anthranilic acid at Cooling the previously unknown molecular compound bis (anthranilic acid) -y-hexachlorocyclohexane arises. Taking advantage of this knowledge, it was found that pure γ-isomer from isomer mixtures of hexachlorocyclohexane, in particular from isomer mixtures, which contain at least 25% y and at least 30 ° / 0 d isomer, by formation a molecular compound of the y-isomer, secretion of the resulting molecular compound and separating off the y-isomer contained in it after splitting the molecular compound can be isolated if anthranilic acid is used as a component of the molecular compound will. According to the invention, pure γ-isomer can be obtained from isomer mixtures are obtained, the at least 25% y-isomer in addition to mainly a- and b-isomer contain the hexachlorocyclohexane if such a starting mixture with at least double the weight of trichlorethylene is stirred, then the separated liquid components of this extraction mixture by evaporation to at least half of its volume continues to be concentrated when added to the concentrated mixture Methanol and anthranilic acid are added and after heating this mixture the crystalline bis- (anthranilic acid) -y-hexachlorocyclohexane produced by cooling severed and is washed at the same time or thereafter, whereupon the separated Molecular compound in a mixture containing methanol and water under heat dissolved and separated off the crystalline γ-hexachlorocyclohexane obtained by cooling and washed with hot water if necessary.

Example 90 g of a technical hexachlorocyclohexane isomer mixture, that in the course of the work-up of crude hexachlorocyclohexane from the after extraction with paraffin hydrocarbons and separation of the 60 to 70% y-hexachlorocyclohexane remaining mother liquor residues obtained by recrystallization using methanol and the 3001, y-isomer, about 30 ° / 0 each a- and b-isomer of hexachlorocyclohexane as well as other chlorine substitution products are included within 1 hour 120 ml of trichlorethylene stirred; then the liquid parts of the mixture sucked through a frit. 70 ml of trichlorethylene are distilled off from the solution. 45 ml of methanol and 35 g of anthranilic acid are added to the concentrated mixture, wherein the mixture is heated to boiling. The mixture is then cooled whereby a crystalline precipitate of bis (anthranilic acid) -y-hexachlorocyclohexane arises. The mixture is left to stand for a long time, expediently 24 to 48 hours. The crystalline molecular compound is then bis- (anthranilic acid) -y-hexachlorocyclohexane separated from the mother liquor by filtration and poured on the filter with 100 ml of mineral spirits washed out. 27 g of crystalline molecular compound with a melting point of 127 ° C. are obtained.

The separated molecular compound bis (anthranilic acid) y-hexachlorocyclohexane is in 300 ml of a mixture of 5 parts by volume of methanol and 2 parts by volume of water dissolved in the boiling point. The crystalline formed after cooling this solution The sediment is filtered off with suction and washed with 250 ml of boiling water.

After drying, it represents a pure γ-hexachlorocyclohexane with a melting point 113.5 ° C (according to Kofler).

The yield is 11 g of pure γ-hexachlorocyclohexane, that is 40,010 of the y-isomer contained in the starting mixture.

PATENT CLAIM: 1. Process for the separation of pure y-isomer from isomer mixtures of hexachlorocyclohexane, in particular from isomer mixtures, contain the y- and d-isomer, by forming a molecular compound of the y-isomer, Separation of the resulting molecular compound and isolation of that contained in it y-isomers after splitting the molecular compound, characterized in that as Component of the molecular compound anthranilic acid used and a mixture of isomers of hexachlorocyclohexane is used as starting material, which is at least 25% y-isomer in addition to mainly a- and d-hexachlorocyclohexane, but at least 30010 6-hexachlorocyclohexane.

Claims (1)

2. The method according to claim 1, characterized in that the Molecular compound with water and methanol decomposed in the heat. Considered publications: German Patent Specifications No. 967 161, 960096; German interpretative document No. 1043 327.