DE892594C - Process for the production of benzene hexachloride (hexachlorocyclohexane) with a content of ª † -isomer of at least 20 percent by weight - Google Patents

Description

Process for the production of benzene hexachloride (hexachlorocyclohexane) with a content of γ-isomer of at least 20 percent by weight. The invention relates on improvements in the production of Benzolhexachlori.d with a relative high proportion of the y-isomer.

It is well known that of the known isomers of r, 2, 3, 4, 5, 6-hexach; lorcycloh @ exan the y-isomer is an effective insecticide, while, the other isomers are relatively inactive in this regard. Usually Benzene hexachloride is produced by an additive chlorination of benzene takes place at temperatures of 2o to 8o ° in the presence of actinic light, and the mean content of the II-isomer is then between about 14%. This Raw product can be used directly in pesticides -, verden, being the 88 to 861 / o of the other isomers and the impurities as part of the diluent or act as a carrier material. Otherwise the pure y-isomer and various y-concentrates produced by the following solvent extraction process will. These concentrates are sufficiently effective on their own, however, there is one method for the direct production of a benzene hexachloride with a high proportion of the active y-isomers are extremely desirable from an economic point of view, especially if moreover the proportion of undesired a-isomer (which is formed at the same time) is also reduced will.

Various methods have been proposed over the past few years to where a co-solvent is used to in the Benzene hexachloride: d to get a larger proportion of the y-isomer. For example, in the Belgian patent 4711 772 proposed that a content of y-isomer of up to 40% can be obtained when gaseous chlorine is present with benzene an aliphatic, polyhalogenated compound, such as chloroform, reacted will. This reaction takes place in a glass apparatus, but the drawing leaves this Belgian patent does not recognize that an exposure of the reaction mixture he follows. Since no coolants are mentioned in the patent specification mentioned, the reaction, which is known to be exothermic, appears to be the usual carried out at elevated temperatures. In British Patent 637,732 is described a product with an increased γ-isomer content, which was caused by chlorination is obtained from benzene under the action of light: that dissolves up to 10% chloroform and contains the precipitated benzene hexachloride, which mainly consists of a- and f-isomers and that comes from previous Clorieru: ngsbehandlun: gene. Finally, it has also been suggested to use benzene in the presence of one or more To chlorinate solvents such as methylene chloride, methylene bromide, methylene chlorobromide, Chloroform, ethylidene chloride, ethylene chloride or ethylene chlorobromide. Here is a greater content of y-isomers of 16 to 19.7% obtained when the reaction is im Darken at temperatures between 21 and 50 ° in the presence of an organic peroxide or propylene gas is carried out as a catalyst. There: were also attempts at the chlorination of benzene under the same conditions in the presence of a number other halogenated aliphatic hydrocarbons performed, however found that all of these either adversely affect the addition reaction or cause no substantial increase in the proportion of γ-isomer. So is for example stated that ethyl chloride adversely affects the reaction and that the proportion of y-isomer, which in the small amount of the benzene hexachloride formed is present, not significantly above the normal 12-14%, and above the addition Carbon tetrachloride is said to have both adverse effects on the reaction influenced and a lower formation of γ-isomer takes place. If the Peroxide catalyst is replaced by irradiation with actinic light and the other conditions remain the same, then the highest yield of y-isomers is 14.6% when methylene chloride is present, while the yield when using others Solvent is generally between 13 and 14%.

In all of these processes, the reaction is carried out at room temperature or slightly increased temperature, generally between 20 and 50 °.

An additive chlorination of benzene at low temperatures was made first proposed in U.S. Patent 2,010,841 and then in U.S. Patent No. 2,010,841 British patent 637 41-2 a process for the preparation of a benzene hexachloride: ds with improved insecticidal properties that are free from substitution products is by making a solution of benzene in an inert solvent in the presence of Light at a temperature between the crystallization temperature of benzene, i.e. H. 6 °, and the crystallization temperature of the benzene-solvent mixture is chlorinated will.

It is stated that by this. Process the shortcomings that the Method of the USA. Patent 2 oio 8qzz adhering, avoided, in particular the need to work under pressure or a temperature lower than -34a to maintain. Tetra chloride is the only compound that eats which is given as an example of an inert solvent, but it is indicated that this condition does not necessarily apply to connections, which are saturated with chlorine, but on any solvent of benzene which is indifferent is against chlorine under the reaction conditions under which this process was carried out will. It can therefore be assumed that partially chlorinated hydrocarbons as solvents should be excluded, those with chlorine at the low Temperatures react.

Although nothing about it in said British patent specification 637,412 is mentioned, it was found that in the chlorination of benzene in the presence carbon tetrachloride not only gives a better product that is free of substitution products and, moreover, a higher content of the y-isomer than usual. Thus, by chlorinating a solution of benzene in carbon tetrachloride in the presence of actinic light and at temperatures from 0 to -50 ° a benzene hexachloride obtained -which has a y isomeric content of 20%, but this appears Value to represent the maximum, which using this particular solvent is attainable.

It has now been found that it is possible to obtain even higher levels to achieve the y-; isomer when the photochemical chlorination: g of benzene with low temperatures in the presence of certain solvents which lead to the Belong to group of partially chlorinated aliphatic hydrocarbons.

During the photochlorination of benzene in the presence of special solvents are the proportions in which the isomers of benzene hexachloride are formed, to a large extent dependent on the temperature at which the reaction is carried out, and there is a relationship between the reaction temperature and the amount of the y-isomer in the product. The preferred formation of y-isomers is to a certain extent Measures favored by changing the reaction conditions, such as the ratio from benzene to solvent "the extent of the benzene conversion and the intensity the exposure, jedloch, is hot the reaction in any solvent of the species mentioned, the reaction temperature evidently at temperatures below d ° the single most important factor regarding the accumulation of benzene hexachloride of y-isomer.

At the working temperatures of 2o to 5d ° were previously different in photochlorination in the presence of solvents Results achieved. As already mentioned, it was stated that a yield of 40 '/ 0 y- # isomer can be achieved when the reaction is carried out in the presence of chloroform is carried out, however, other researchers reported that the γ-isomer content hardly changes compared to the usual 12 to 1q.0 / 0, which in the absence of a Solvent can be achieved. This indication could be confirmed when the reaction carried out under the usual conditions of exposure, supply of chlorine and the like as it is done in the usual production of benzene hexachloride.

However, as the reaction temperature is decreased, the proportion of γ-isomer in the product increases to a maximum amount which coincides with a certain optimal temperature. If the reaction temperature is lowered below this optimal temperature, the content of γ-isomer begins to decrease. If the reaction temperature is plotted against the isomer content of the product in the form of a curve, it can be seen that the γ-isomer content rises to a maximum when the temperature falls from 30 to -15 and to -3o °. This maximum changes depending on the solvent used, and it has been found that in certain cases, especially when using methylene chloride or ethylene dichloride as solvent, this can be 27 to 280 / a: The reaction temperature at which the maximum Formation of the y-isomer occurs, also changes with the solvent, but is generally in the vicinity of -15 to -4o °.

At low temperatures, i. H. those below 0 °, the benzene dissolves a considerable amount of chlorine, and the concentration obtained causes the exothermic reaction between benzene and chlorine, which .by the action of light is initiated, is quick and therefore difficult to control the temperature is. Under these working conditions and in the absence of retarders such as the well-known reaction retarders oxygen, Sticl: oxydul or hydroquinone found that in the presence of certain saturated chlorinated aliphatic Hydrocarbons which are suitable at the reaction temperature used to form a liquid mixture with the benzene, this disadvantage can be overcome can and also in some way that has not yet been clarified, the percentage content of y-isomer in the benzene hexachloride formed is increased can be. Furthermore, it was found that the delay effect, which in The presence of certain solvents at higher temperatures does not always occur can be determined at low temperatures. For example, ethyl chloride retards the formation of benzene hexachloride at temperatures from 20 to 50 °, but this phenomenon is not detectable at lower temperatures.

Thus, according to the invention, there is provided a method for producing benzene hexachloride with a content of y-isomers of at least 2i0% proposed, which consists in that chlorine in a liquid mixture of benzene and one or more solvents partially chlorinated aliphatic hydrocarbons is introduced, e.g. B. methyl chloride, Methylene chloride, chloroform, ethyl chloride, i, i-dichloroethane, ethylene dichloride, i, i, 2-trichloroethane, symm.-Tetracli: loriä @ than, propylene dichloride, i-Chl, or-i-methylpropane, Butyl chloride, tert-butylchlori, d, i, 2-dichloro-isobutane :, monofluorodichloromethane and i, i-difluoro-i, a-dichloroethane, the reaction being carried out at a temperature between o and -5ö ° in the presence of actinic light and in the absence of retarders the addition reaction between benzene and chlorine is carried out.

The proportion of y-isomer formed depends on the solvent used from, and if the reaction in methyl chloride, methylene chloride and Äthylendich.lorid is carried out, results, for example, a content of y-isomer between. 24 and 28%. The total yield of benzoil hexachloride calculated on the applied Amount of chlorine depends to a certain extent on the type of solvent used and it was found that the best yields in the presence of methane and ethane derivatives are obtained and that the yield generally increases by reducing the reaction temperature. In certain cases, in particular when using monochlorinated butanes, the yield of benzene hexachloride is even when using low temperatures, very little, and the chlorine reacts predominantly with the solvent, but here too it should be noted that the proportion of γ-isomer in the benzene hexachloride formed is increased.

The yield of benzene hexachloride, d, calculated on the amount of consumed Benzene changes only very little, if at all, when the reaction conditions are changed. Experience has shown that the yield of Beiizolhexachlorid from the with Chlorine reacted benzene is usually almost 100%, and in practical work with the usual precautions for recovering unconverted benzene the benzene utilization will always be above 95%.

In one embodiment of the invention, a mixture of benzene and solvent in a glass vessel or in a glass-lined vessel, which with a supply pipe for the chlorine, a stirring device, cooling device and means for exposing the vessel to light with a suitable light Wavelength is equipped. The light should preferably be within the range the continuous absorption for the chlorine molecule, d. H. between ¢ 50o and 2500 A, and mercury vapor lamps, which emit light of these wavelengths, for example, mercury vapor lamps operating at medium pressure give beneficial results. It was not found that the strength of the exposure is unusually decisive, but it has been found, for example, that an O_uecksilberdampflampe operating under medium pressure, which an exposure from goo Lux at a distance of one meter, represents a sufficient source of exposure, when placed at a distance of 20 cm from the reaction zone.

It is desirable to remove any oxygen present as this is known to delay the photochlorination, which is why the one in the vessel Air by an inert gas or steam, such as carbon dioxide, or nitrogen is displaced by one of the constituents of the reaction mixture. It is also it goes without saying that, substances which are known to have chlorine substitution favor with benzene, should not be present. Then chlorine is added to the mixture and the temperature is increased substantially by cooling during the reaction kept constant. Depending on the amount of chlorine added, benzene is converted into Bennzol hexaahloride transferred, and the reaction mixture is then worked up in a known manner, for example by removing the solvent and benzene by evaporation or steam distillation or by letting the benzene hexachloride crystallize out. If the benzene conversion is high, the liquid product is a supersaturated one Is a solution from which the benzene hexachloride separates out when left to stand, without that a special # evaporation takes place. However, it may be necessary first to remove a certain part of the solvent, especially in the case in which only a slight conversion of benzene has taken place. The crystallization process is preferred, as this not only makes the solid product in one extraordinary pure and easily filterable state is obtained, but also 'none Drying of the product and the solvent is necessary. Furthermore, that there is no loss of solvent due to its poor solubility in water. With regard to the quality of the product, this is the subject of the invention forming processes the older processes, which at higher temperature and in the absence a solvent are carried out, significantly superior, because with these it is difficult to obtain the isomeric mixture in a pure and non-sticky form. The crystallized or precipitated benzene hexachloride is then filtered and dried. The proportion of the various isomers! Can be determined by infrared spectrography to be appreciated. The amount of chlorine used in this reaction and accordingly the percentage of benzene converted does not seem remarkable To have an influence on the ratio of isomers in the product. At a high However, benzene conversion has a certain substitution and addition chlorination of benzene instead, and there can also be a certain amount of C'hlo-. ration of the solvent take place if this is possible, which naturally reduces the economy of the reaction, based on the chlorine consumption, decreases somewhat. On the other hand, has a low conversion value a greater consumption of solvent result. Although that is the subject of the Invention-forming processes do not rely on a specific ratio of chlorine to benzene is limited, it has been found to be advantageous to use sufficient chlorine, in order to carry out a conversion of the benzene between 9 and 60%.

Apart from the ability to change the isomer ratio: se of Benzolhexachlorild change, the chlorinated hydrocarbon solvent initially acts as a thinning agent, which serves to distribute the heat of reaction and to maintain a constant temperature, and continue as a means of getting a liquid iMixture with benzene even at low levels Maintain temperatures. Benzene crystallizes at about 6 °, but is mixed with the other solvents, the resulting mixtures are lower Points of crystallization as those of each of its constituent parts.

The amount of solvent used is not important, and she can; change within wide limits. So this - for example up to make up 99% of the mixture. The lower limit depends, of course, essentially on the formation of a suitable liquid mixture at the desired reaction temperature ab, unid this is determined by practical working conditions. Through the present of too much. Solids in the mixture, such as benzene crystals, will an effective agitation inhibited, -which is necessary to a good temperature control carry out, this would continue the passage of light and heat through the mixture is inhibited and so indirectly the formation of the desired y-isomer be hindered. A mixture of 3 parts solvent is used in all examples and i part of benzene is used. By changing this ratio within the limits, which are required to maintain a liquid mixture becomes the The proportion of γ-isomers in the product is not significantly influenced.

Some embodiments of the invention are described in the following examples. EXAMPLE 1 A series of experiments were carried out between 0 and -50 ° with temperature intervals of 5 °, in which 1 mol of benzene was treated with 3 mol of methylene chloride in a closed, glass vessel for 2 to 6 mol of chlorine and the light source consisted of an oued silver vapor lamp, which was a emitted effective light at a wavelength of essentially 4358 Å . The vessel was provided with suitable means for cooling the reaction mixture to the desired temperature. Before introducing the chlorine, the air was removed from the vessel with carbon dioxide.

The amount of chlorine used is sufficient to deal with about 91 / o of the benzene to combine, and the feed rate was 5 mg of chlorine per gram of benzene, the was originally present, every minute. Towards the end of the reaction, the excess was ß removed from benzene and solvent by steam distillation and the remaining solid product dried and then subjected to infrared analysis. The content of y isomer was also determined with the aid of the polarograph and through application tests as a pesticide, and the results obtained were in good agreement with those from the infrared estimate.

The products were hard, white, easily ground, solids, and the proportions of the four isomers they contain are shown in the following table: Table I. Chlorination in the presence of methylene chloride Temperature Percentage of benzene hexachloride isomers ° cy I a I , BJ h 0 21 62 3 3 - 5 20 62 3 5 - xo 20 65 4 4 -15 25 63 3 6 - 20 24 56 4 4 -25 26 55 .5 4 -30 26 58 6 5 = 35 28 53 6 6 -40 25 52 7 7 -45 24 49 9 9 -50 23 54 9 10 From these values, 'it follows that a' content of y-isomers of 2, o 0/0 and more within a wide temperature range er! H ', is old and that the maximum formation of this isomer at a temperature of about - 35 ° takes place. This process enables the normal y-isomer content to be doubled.

The reaction takes place rapidly up to the temperature of the maximum y-Is, formation of omers, however, it becomes slower as this temperature is lowered further. The economy, based on the chlorine consumption, can generally be described as good.

For comparison purposes, further tests were carried out under the same conditions with the exception that the temperatures were kept above 0 °. In these experiments the γ-isomer content of the benzene hexachloride obtained was 14 to 19%. The results set out in Table I and others obtained from comparative experiments are shown graphically in the drawing, with the reaction temperatures plotted on the horizontal and the content of the four isomers on the vertical, each of which is calculated as a percentage of the total isomer content became, ie therefore (a + y -h ß -f- d) = ioo. The values obtained are essentially on the four curves A, B, C and D of the drawing. This drawing shows the gradual increase in the y-isomer content (curve C) up to a maximum, followed by a sharp drop, and the steady, steady decrease in the a-content (curve A). The proportion of β and β isomers (curves B and D) changes very little until the maximum formation of γ isomers is reached, after which they then increase as the γ content falls. Example e In a mixture of .i times benzene and 3 times ethylene dichloride, 0.25 moles of chlorine were added at a rate of io. g per gram of Co H "per i @ linute. Five experiments were carried out with this mixture, each with iis ° temperature intervals, the working conditions and the analysis of the products being similar to those in Example i. The benzene hexachloride obtained in each case was a hard, white and brittle material, and the reaction proceeded rapidly throughout the process. The yield was very good at temperatures of -15 ° and below. The following table shows the percentages of γ-isomer: Table 2 Chlorination in the presence of ethylene dichloride Temperature percentage of y-isomer c O 22 -I5 24 -30 27 -45 26 -49 to -57 22 When a similar experiment was carried out at a temperature of 15 °, the yield was low and the γ-isomer content was 15%. EXAMPLE 3 A number of experiments were carried out within the temperature range from 0 ° to -40 ° in the presence of i, i, 2-trichloroethane, the proportions of benzene, chlorine and solvent, the feed rate of chlorine and the other working conditions being similar as in Example 2. In this case too, the products were completely satisfactory, the reaction proceeded rapidly and the yield was good. The temperature of the maximum formation of the y-isomer was about -1 5 ". Table 3 Chlorination in the presence of i, @i, 2-trichloroethane Temperature percentage of y-isomer ° C 0 23 -15 24 -30 22 -45 17 When similar experiments were carried out at 30 and 15 °, the γ-isomer content of the product was 14 and 18%.

EXAMPLE 4 i, 2-dichloropropari or propylene dichloride were used as solvents in the following four experiments, the amounts of reactants and the reaction conditions being the same as in example 2. The reaction proceeded rubbishly, and the products were below operating temperatures -i5 '° very good. The yield was not good at the higher temperatures and improved as the temperature was lowered. - Table 4 - Chlorination in the presence of propylene dichloride Temperature percentage of y-isomer ° C 0 - i9 _i5 23 -30 24 -45 20 A comparative experiment carried out at 15 ° gave a low yield of benzene hexachloride, which contained only ii% γ-isomer.

Example s The chlorination was carried out in the presence of monofluorodichloromethane. Otherwise, the conditions were the same as in Example-2, "where" an increase in the 7, content up to a maximum was also found. The products and yields were good, and the reaction proceeded rapidly in the higher temperature range; however, it decreased again as the temperature fell. Table 5 Chlorination in the presence of Monofluorodichloromethane Temperature percentage of y-isomer O 20 -i5 21 -30 21 -45 18 -6o = Z - Example 6 In order to adapt the process forming the subject of the invention to a continuous working method, a series of experiments were carried out at -35 °, 1 mole of benzene mixed with 3 moles of methylene chloride in a closed vessel being reacted with 01.25 moles of chlorine and the light source consisted of a medium pressure mercury vapor lamp.

The air was first removed from your vessel with carbon dioxide. The rate of supply of chlorine was 100 mg per gram of benzene per minute. At the At the end of the reaction, the precipitate formed was filtered off at -35 °.

Corresponding amounts of benzene and methylene chloride were added to the filtrate supplied to replace the benzene converted into benzene hexachloride again and to compensate for the loss of benzene and methylene chloride. The filtrate was then . returned to the reaction vessel and in the manner indicated above with further o #, 25 moles of chlorine chlorinated, whereupon the precipitate is filtered off again and the working treatments were repeated continuously. After a number of working cycles, that was it The filtrate is saturated with the various benzene hexachloride isomers, and almost the whole quantities of this newly formed benzene hexachl, orsidis. crystallized out.

The mean content of γ-isomers of the benzene hexachloride formed was 24010.

The recycling of the filtrates had no harmful effect the reaction and also not to Ida's product, and 'on filtering resulted in a -Material: with improved physical appearance compared to: the one which was obtained by processes in which the product is heated and / or was melted. Example ? Chlorine, benzene and methylene chloride were in the molar ratios of 0.25: -1: 3 continuously to a dark one provided with a stirrer Vessel or a dissolution device fed, which was cooled to -38 °. the Mixture was continuously poured onto the inner surface of the reaction vessel, that had cooled down to -5o ° and that with two under medium pressure Onecksil'.berdampflampern # was exposed. The air rose from your dissolving fluid purged from the reaction vessel with nitrogen. The Alblauf became the steam distillation subjected to remove the solvent and excess benzene, and d'as product dried and analyzed in the usual way. That on this Benzene hexachloride so prepared had very good physical properties and contained 250 / a y-isomer ..

In addition to the experiments described in Examples i to 7, further experiments were carried out under similar conditions to determine the effect of other chlorinated - aliphatic hydrocarbons as solvents in the chlorination of. To test benzene under the temperature conditions used according to the invention. A summary: of these tests together with those as described in: the aforementioned examples can be found in the following table 6. The temperature which is given in the last column of this table is that at which in each case the maximum Y-isomer content occurs, and this temperature was taken from a curve in which the y-isomer content of the product was entered as a function of the working temperature in each experiment. Table 6 Approximate Temperature percent temperature the Solvent area retention at maximum y-isomer -y formation ° c ° c Methyl chloride. . . . -30 24 Methylene chloride .. o to -501 2o-28 -35 Chloroform ....... -i5 20 Ethyl chloride ...... -i5 to -45 2i-22 -24 i, i-dichloroethane. o - -i5 20 - g Ethylene dichloride. . O - -50 22-27 -30 i, i, 2-trichloro ethane ........ 0 - -30 '22 -24 -i5 symm.-tetrachlor- ethane .......... o - -45 2o-23 -i5 Propylene dichloride. -i5 - -45 2o-24 -27 i-chloro-i-methyl- propane ....... -i5 21 Butyl chloride ..... -3o - -45 2o-22 -30 tert-butyl chloride. o - -45 2o-21 -45 i, 2-dichloro isobutane ....... -3o 21 Monofluoro dichloro methane. . . . . . . . o - -30 20-2i -20 i, i-difluoro i, 2-dichloroethane -30 24 In most cases, with the exception of those in which monochlorinated butane derivatives were used, the yields were good. Although these solvents gave a product with a high y- @ content, they themselves reacted to some extent with chlorine, which shows that a considerable amount of hydrogen chloride was evolved. However, the dichloro derivative of butane gave a satisfactory yield of a product of good appearance.

When using i, 2-Diahlo, r-i, i-d @ ifluoroethane as solvent was: the product was satisfactory and @ had a high y-content: t, and the yield was good, but the response was quite slow compared to the already mentioned chlorinated methanes and ethanes.

Claims (7)

PATENT CLAIMS: i. Process for the production of benzene hexachloride (Hexachlorocyclohexane) with a content of y-isomer of at least 2o percent by weight by additive chlorination of benzene, characterized in that one ate chlorine in partially a liquid mixture of benzene and one or more solvents chlorinated aliphatic hydrocarbons such as methyl chloride, methylene chloride, Chloroform, ethyl chloride, i, i-dichloroethane, ethylene dichloride, i, i, 2-trichloroethane, symm.-Tetrachloräth@an, propylene dichloride, i - chlorine - i - methylpropane, butyl chloride, tert-butyl chloride, @i, 2-dichloroisobutane, monofluorodichloromethane and i, i-Difluo.r-i, 2-dichloroethane at a temperature between o and -5; o ° in the presence of actinic Initiates light and in the absence of retarders of chlorine addition. 2. Procedure according to claim i, characterized in that at a temperature of -i5 to -40 ° is being worked on. 3. The method according to claim i and 2, characterized in that in the presence of methylene chloride at a temperature between -25 and -4o ° in the presence of ethylene dichloride between -25 and -35 ° and in the presence of i, i, z-trichloroethane between -io and -2o ° is used. 4. The method according to claim i to 3, characterized characterized in that the ratio of solvent to benzene in the mixture is about 3: i moles. 5. The method according to claim i to 4, characterized in that an amount of chlorine is introduced into the reaction mixture such that g to 60 ° / a of benzene can be converted into benzene hexachloride. 6. The method according to claim i to 5, characterized in that the chlorination is carried out continuously will. 7. The method according to claim 6, characterized in that the filtrate according to filtering off the precipitated benzene hexachloride into the reaction vessel again is returned. Referenced Documents: British Patent Specification No. 637 412, 637,732; Belgian patent specification No. 471 772.