DE4111906A1 - Mono:chloro-acetonitrile prepn. - by chlorination of acetonitrile saturated with hydrogen chloride - Google Patents

Abstract

Prepn. of monochloroacetonitrile (I) comprises chlorination of HCl-satd.-MeCN. (esp. undiluted) with Cl2 at 40-125 deg.C, opt. with irradiation or in the presence of a radical catalyst. Chlorination is carried out by simultaneous addn. of Cl2 and MeCN into an appts. with a turnover of MeCN of 0.1-30%, and removal of chlorinated MeCN from the appts. Use of (I) in synthesis of trichloroacetonitrile (II) by further chlorination, is also claimed. USE - (I) is an intermediate in the synthesis of dye intermediates, substd. pyridines, insecticides and rubber auxiliaries. It may e.g. be reacted with trichloromethyl-isocyanide-dichloride to give tetrachloro-pyrimidine, an important reagent in prepn. of reactive dyes. (II) is useful in organic syntheses. The process gives good yields and is selective. The prepn. of (II) from (I). also gives good yields, unlike known processes for sump chlorination of MeCN which lead to formation of large quantities of a triazine deriv.

Description

The present invention relates to a new method for producing the known monochloroacetonitrile, which is an intermediate for the synthesis of substituted pyridines, for the synthesis of biologically active compounds such as for example insecticides (especially against aphids), also for the synthesis of Rubber auxiliaries or dye intermediates are used can.

It is already known that monochloroacetonitrile by gas phase chlorination preserved at elevated temperature. However, there is a defect in this process that large throughputs per unit of space and time are not possible (Lit. DL 841 78.R (H. Seeboth and R. Nitschke), as well as Chem. Techn. 23 vol. Issue 12, 1971; US 31 21 735; Japan 9326/67; YES 71 11 489-R; USSR 5 16 682 (1976); E.M. Movsum. Zade. M.G. Mamedov et al. L.A. Shikiev, Khim. Proms-zt. (Mos. 53, 1977, 9662) Bull. Soc. Chim. Belg. 61 366 (1952)), or that the chlorination of Acetonitrile provides practically only trichloroacetonitrile (US 39 23 860 and US 34 18 228).

However, experiments on chlorination in the liquid phase are also described. In Houben Weyl, Methods of Organic Chemistry Volume V / 3. S 634 Georg Thieme Verlag Stuttgart 1962 the chlorination of acetonitrile in the liquid phase is under Irradiation with UV light in the presence of HCl gas is described. You feed however only trichloroacetonitrile.  

Likewise, the chlorination of acetonitrile in the presence of J ₂ as a catalyst only leads to trichloroacetonitrile. To avoid the formation of trichloroacetonitrile, chlorination at relatively low temperatures was also attempted, with chlorination only up to a certain conversion. However, the yield is only 40% of theory. Th. (US 38 25 581). In this document, however, one also finds the indication that when the acetonitrile is chlorinated above 50 ° C., for. B. at 70 ° C, only tri chloroacetonitrile is obtained.

Furthermore, it is known from EP-9 788 that acetonitrile can be chlorinated in the presence of vaporizable catalysts such as SnCl ₄ . However, this method has the disadvantage that traces of the catalyst can be removed only with great difficulty and with great effort after the chlorination has ended, so that there is also a risk of triazine being formed.

A method has now been found which is the direct chlorination of the acetonitrile to monochloroacetonitrile in high selectivity and at the same time high yield allowed. The chlorination takes place according to the following scheme:

HCl-saturated acetonitrile is used in a suitable one according to the invention Equipment (comparatively similar to DE 27 16 896 in structure) with elementary Chlorine at temperatures between about 40 ° and 125 ° C, preferably undiluted, optionally under exposure or in the presence of a radical catalyst chlorinated, the chlorination of the running through the chlorination zone Acetonitrile is carried out at a conversion between 0.1 and 30% simultaneous addition of chlorine and acetonitrile to the apparatus and removal of chlorinated acetonitrile from the apparatus.  

It is extremely surprising that this liquid phase partial chlorination, in high Yields with the preferred formation of monochloroacetonitrile expires. Rather, it had to be expected from the cited prior art that the product ratio of monochloroacetonitrile to undesirable products, e.g. B. Trichloroacetonitrile, much less favorable and a work-up to the desired one Monochloroacetonitrile is very expensive.

Due to the special reaction procedure, there is not only a higher one Reaction rate, but also at least 3.5 times higher Space / time yield, compared to EP 9 788.

The process according to the invention can be carried out in the presence of diluents be carried out, with the usual inert for halogenation reactions Solvents such as dichloromethane, chloroform, carbon tetrachloride or Frigene, e.g. B. Frigen 22, are suitable. However, tetra is preferably used chloromethane.

However, the process according to the invention is preferably carried out without adding Ver fertilizers and preferably carried out at normal pressure.

The direct chlorination of acetonitrile can optionally with exposure to UV light or by adding suitable radical catalysts be performed.

For example, a water-cooled mercury high can be used as the UV light source pressure burner can be used as a diving lamp or from the outside can be brought. When attaching the lamp, make sure that as much light as possible enters the halogenation zone. All for such Halogenations customary high-pressure mercury burners can be used for the invention Use procedure. Of course, others are also for such Halogenations suitable light sources can be used.  

Peroxide, for example, can preferably be used as radical catalysts Cumyl peroxide or benzoyl peroxide, or azo compounds such as Use azoisobutyronitrile (AIBN).

If the process is carried out in the presence of catalysts, per mole of acetonitrile in general 0.001 to 1.5 mol%, preferably 0.02 to 1 mol%, and particularly preferably 0.1 to 0.5 mol% of catalyst.

The reaction temperatures can be carried out when carrying out the inventive Process can be varied over a wide range. Generally you work as indicated above, at temperatures between 40 ° C and 125 ° C, preferred between 60 ° C and 110 ° C, particularly preferably between 80 ° C and 100 ° C. In particular, one works at temperatures in the boiling range of the acetonitrile to be chlorinated. It is extremely surprising that in this temperature range monochloroacetonitrile according to the invention Process is obtained and not trichloroacetonitrile as the literature (US 34 18 228) predicts.

The process according to the invention can be carried out in a "batchwise" (i.e. discontinuous lichen) (variant 1) and in a continuous driving style (variant 2) be performed.

The chlorination process of acetonitrile according to the invention will now be so gonnen that in an appropriate apparatus with acetonitrile at the boiling point HCl gas is saturated and then HCl-saturated acetronitrile under Exposure at or slightly below boiling point with elemental chlorine is fed to a flooded reaction zone after mixing (mechanical or by the current), carried out by appropriate measures in front of a Backmixing protected with fresh chlorine and after chlorination has ended reaction is fed to a column.

This mixture of starting material and product of formula (I) is in the column separated, the product collecting at the bottom of the column and the abge  separated educt saturated with HCl is fed back to the chlorination zone (variant 1). This continues until all of the acetonitrile used has reacted.

The chlorinated acetronitrile (collected at the bottom of the column) can in the case sufficient purity used directly for further implementations or a fine be subjected to fractionation.

Is continuously separated from the column with HCl-saturated acetonitrile fresh acetonitrile added and at the same time with chlorine in the flooded Entered reaction zone, so a continuously working process arises, (Variant 2), in which ultimately educt and chlorine are constantly added and Reaction product is removed from the apparatus.

It is only important to ensure that after mixing HCl-saturated acetonitrile and chlorine in the reaction zone a sufficiently long residence time until the end chlorination and backmixing with fresh chlorine as well as direct Escape of the HCl gas formed is prevented.

Mixing of the chlorine in the reaction zone can e.g. B. by stirring the flow of the reactants when added in a venturi tube or a combination of these possibilities as well as other possible suitable advantages directions.

The backmixing of the reaction mixture in the reaction zone with fresh HCl-saturated educt and chlorine can be prevented by constant removal the, the reaction mixture after leaving the reaction zone in a vessel is directed, whose geometry is designed so that the flow time or Dwell time under exposure is as long or slightly longer than the time required for a complete implementation of the added chlorine is necessary, for example Pipe with the appropriate diameter, possibly filled with glass fillers, represent such a reaction vessel. Of course, other suitable ones are also Vessels conceivable. The residence time of the reaction mixture under exposure can thereby be enlarged so far that the chlorine until it enters the  Separation column is fully implemented and only then formed HCl gas from the Reaction mixture can escape.

The chlorination of the acetonitrile passing through the chlorination zone is both with batch (variant 1) as well as with continuous driving (Variant 2) with a conversion between 0.1 and 30%, preferably between 2 and 20%, particularly preferably between 5 and 15%, so that in total together with chlorine and acetonitrile supplied to the apparatus and chlorinated acetonitrile without Educt of the apparatus can be removed.

As a rule, in batchwise chlorination (variant 1) up to about 95% Turnover (100% starting material used minus starting material still present after the end Chlorination) of the total educt used chlorinated. Then the reaction canceled and the approach fractionated.

The reaction can be interrupted in both variants and the process after a few Time to be continued. The reaction mixture can also be stored temporarily and can only be processed after some time.

As a rule, however, one batch is chlorinated without interruption and then fractionated immediately.

In principle, the bromination of acetonitrile is also possible using this process.

In this way, monochloroacetonitrile is obtained with high selectivity and Yield, while the formation of by-products is kept low. With a relatively small equipment can be achieved through the continuous procedure (Variant 2) large quantities of the desired product per unit of space and time synthesize, with only small amounts of di- and trichloroacetonitrile as By-products arise. The reaction remaining in the reaction zone The mixture can be reused for further batches in batch chlorination be applied.  

Of course, it is also possible to use monochloroacetonitrile according to the following scheme chlorinate the above process further:

This process provides good yields of trichioracetonitrile, which is used for the Synthesis of organic compounds serves as an intermediate. This connection can also be produced by dewatering trichloroacetamide. Also ent it also stands for the direct bottom chlorination of acetonitrile, although a Much of the trichloroacetonitrile turns into a triazine according to the following equation implemented and therefore the yield of isolable trichloroacetonitrile is lost. (Lit. JA 71 11 664-R; Bull. Chem. Soc. Japan 44 (1971) 1,148; Bull. Chem. Soc. Japan 42 (1969) 11, 3242).

Trichloroacetonitrile is an important intermediate for dye synthesis. Monochloroacetonitrile can also be used, for example Trichloromethyl isocyanide dichloride to tetrachloropyrimidine, an important Implement block for the synthesis of reactive dyes (Le A 10 692 = DOS 16 70 854):  

The process according to the invention for the chlorination of acetonitrile to monochlor Acetonitrile is proven by the following experiment:

Process variant 1: batchwise chlorination.

An embodiment of the method according to the invention is explained with the aid of FIG. 1:

In the head ( 3 ) of a column ( 12 ), which has a feed ( 10 ) in the central part and a discharge ( 13 ) at the bottom ( 11 ) and which is designed with packing or glass trays, is ( 1 ) or ( 2 ) initiated the educt.

In the top ( 3 ) of the column, the starting material, here HCl-saturated acetonitrile, evaporates and is fed via the feed line ( 4 ) into the cooler ( 5 ), where it condenses. The condensed acetonitrile is introduced via the feed line ( 7 ) into the reactor ( 9 ), which can optionally be heated or cooled to the desired reaction temperature. The reactor consists of an exposure unit and a reac tion tube which can be spirally shaped. It is designed so that the reaction product is removed as quickly as possible from the mixing zone of starting material and chlorine in order to avoid back-mixing. Gaseous chlorine is fed in via the feed line ( 8 ), for example via a Venturi tube. The chlorination takes place with exposure in the entire flooded reaction zone.

The resulting reaction mixture, which consists essentially of monochloroacetonitrile, unreacted acetonitrile and hydrogen chloride, is passed through the feed ( 10 ) into the central part of the column ( 12 ), where the reaction mixture is separated. The unreacted acetonitrile and the hydrogen chloride are discharged via the top ( 3 ) of the column ( 12 ) and fed via the feed line ( 4 ) to the cooler ( 5 ) in which hydrogen chloride is separated off via the top ( 6 ), while the acetonitrile is in the reaction cycle is continued.

The monochloroacetonitrile formed in the reaction is removed from the apparatus via the bottom ( 11 ) of the column ( 12 ) via the discharge line ( 13 ).

855 g of acetonitrile are initially in an apparatus as described above HCl gas saturated. Chlorine is then passed into the at boiling temperature Chlorination zone of the apparatus under UV exposure with a high pressure Hg burner so that only a partial chlorination of the circulating Acetotutril current occurs. As the chlorination progresses, the Bottom temperature up to 120 ° C. The chlorination is by gas chromatography Analyzes permanently tracked and carried out until the composition of the raw product shows the following analytical values (in percentages):

7.3% CH ₃ CN; 0.5% Cl ₃ C-CN; 89.6% ClCH ₂ CN; 2.5% Cl ₂ HC-CN.

The raw product is then carefully fractionated. Monochloroacetonitrile boils 125 ° C. A total of 1309 g is obtained after refractioning the forerun Monochloroacetonitrile, that is 90.5% of theory, with 7.3% recovered Acetonitrile are deducted from the yield.

Chlorination of the monochloroacetonitrile to trichloroacetonitrile

1043 g of monochloroacetonitrile, which may be saturated beforehand with HCl gas, are sump-chlorinated at 70 ° C. under irradiation with UV light (from an Hg high-pressure burner) by directly introducing chlorine. The progress of the reaction is followed by gas chromatography. If the composition of the chlorination mixture reaches the following values, the chlorination is stopped: 65.1% Cl ₃ C-CN; 17.8% Cl ₃ C-CCl = NCl; + 2.1% + 5.6% + 3.4% + 3.5% various chlorinated triazines; 2.5% educt.

The chlorination residue is fractionated over a packed column. Man receives 99.9% pure trichloroacetonitrile at boiling point 85-86 ° C and at Boiling point bp 80 ° C, 51.8 mbar, 98.5% pure N-chloro-trichloroacetimidoyl chloride (W.P. Trompen, J. Greevers, J.Th. Hackmann, Recl. Trav. Chim. Pays-Bas 1971 90 (5), 458).

Claims (9)

1. A process for the preparation of monochloroacetonitrile, characterized in that HCl-saturated acetonitrile is chlorinated in a suitable apparatus with elemental chlorine at temperatures between about 400 and 125 ° C, preferably undiluted, if appropriate with exposure to light or in the presence of a radical catalyst, wherein the chlorination of the acetonitrile passing through the chlorination zone is carried out at a conversion between 0.1 and 30%, with simultaneous addition of chlorine and acetonitrile to the apparatus and removal of chlorinated acetonitrile from the apparatus. 2. The method according to claim 1, characterized in that at Chlorinated temperatures between 600 and 110 ° C. 3. The method according to claim 1, characterized in that at Chlorinated temperatures between 80 ° and 100 ° C. 4. The method according to claim 1, characterized in that peroxides or azo compounds are used as catalysts. 5. The method according to claim 1, characterized in that one at this Liquid phase partial chlorination equipment used which is the backmix prevent and at the same time the residence time of the reaction mixture Increase the exposure so that the chlorine until it enters the separator column is fully implemented and only then formed HCl gas from the Reaction mixture can escape. 6. The method according to claim 1, characterized in that the Chlo tion of the acetonitrile is carried out batchwise or continuously.   7. The method according to claim 1, characterized in that the chlorination between 2 and 20% of the acetonitrile passing through the chlorination zone Sales is driven. 8. The method according to claim 1, characterized in that the chlorination between 5 and 15% of the acetonitrile passing through the chlorination zone Sales is driven. 9. Use of monochloroacetonitrile for the synthesis of trichloroacetonitrile by further direct chlorination.