DE2020143A1 - Production of mono- (2-cyanoaethyl) -acetonimines and their conversion to 5-oxocapronitrile - Google Patents

Description

Registration number 2170

Dr. F. Zumsteln ten. · Qr. E Assmann Dr. R. Ko »nig» berger · Dipl. Pliya. R. Timber Construction *

Dr. F. Zum3toin jun.

Patent attorneys

8 Munich 2, Bräuhausstrasse 4 / III

STAMICARBON NV, HEERLEN ('the Netherlands )

Production of mono- (2-cyanoethyl) acetonimines and their Conversion to 5-oxocapronitrile

The present invention relates to a method for producing Mono- (2-cyanoethyl) acetonimines by reacting acrylonitrile with an acetonimine and to a process according to which the mono- (2-cyarioethyl) acetonimine obtained if desired, is converted to 5-oxocapronitrile.

From the American patent specification 2,768,962 it is known that the action of acrylonitrile on various ketoimines takes place in stages. First, the acrylonitrile reacts with the ketoimine to form the mono- (2-cyanoethyl) -ketoimine and then, after the ketoimine present has been converted almost entirely into the mono- (2-cyanoethyl) -ketoimine, the latter product continues with Acrylonitrile with the formation of di- (2-cyanoethyl) -ketolmins, the second cyanoethy! Group being bonded to another carbon atom. With a ratio of 1 mole of acrylonitrile to 1 mole of ketoimine, according to the aforementioned American patent, essentially mono- (2-cyanoethyl) ketoimine and with a ratio of 2 moles of acrylonitrile to 1 mole of ketoimine mainly di-'C2-cyanoethyl) -ketoinün GewQö & en. ,

It has now been found that when acrylonitrile reacts with an acetonimine from a gradual action of the acrylonitrile on the acetone is out of the question. At a ratio of 1 mole of acrylonitrile to 1 mole Acetonimine is namely the acrylonitrile mainly in di- (2-cyanoethyl) acetonimine

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implemented. It also turned out that the cyanoethyl groups in di- (2-cyanoethyl) acetonimine, contrary to those made in said American patent Information, are bound to essentially the same carbon atom. The reaction of acrylonitrile with an acetonimine can also be better with compare the known reaction of acrylonitrile with acetone. In this case it is namely, there is also no question of a step-by-step action of the acrylonitrile on the acetone, but it is at a ratio of 1 mole of acrylonitrile to 1 mole Acetone obtained a reaction product in which only a little mono- (2-cyanoethyl) acetone in addition to a large amount of di- (2-cyanoethyl) acetone occurs, while the two cyanoethyl groups in the di- (2-cyanoethyl) acetone essentially on the same carbon atom are bound. It is therefore understandable that in the aforementioned American

™ Niche patent an example regarding the Moiiocyanoäthylierung the most The obvious ketoimine group, namely the acetone imines, is absent.

The present invention now provides a method according to the acrylonitrile can be converted into a mono- (2-cyanoethyl) acetonimine with a very high yield. The inventive method is characterized in that between the Reactants have a ratio of at least 1.5 moles of acetonimine to 1 mole Acrylonitrile used and unconverted from the resulting reaction mixture Acetonimine is recovered and if the reaction product is desired mono- (2-cyanoethyl) acetonimine hydrolyzed to 5-oxocapronitrile.

According to the present invention, the formation of di ~ (2-cyanoethyl) acetonimine can be avoided entirely. This is surprising in particular because of the known reaction of acrylonitrile with acetone, even when using 10 moles of acetone

k per mole of acrylonitrile, the formation of di (2-cyanoethyl) acetone only to a small extent can be restricted (see Journal of American Chemical Society, Volume 75, 1953, Page 3015).

The acrylonitrile can be completely converted in the process according to the invention will. However, a partial conversion of the acrylonitrile is also possible; in this case one can, under the same conditions, with one? shorter ones Be satisfied with the response time. The non-converted acrylonitrile lets through Recover distillation from the reaction mixture. In this case, the temperature of the reaction mixture is preferably kept above 50 C until the nichi: Inverted acrylonitrile has been removed because it has been found that - "" an acrylonitrile-containing reaction mixture at temperatures below 50 C. desired by-products can be formed.

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According to the invention, there are different molar ratios between acetonimine and acrylonitrile, which are larger than 1.5: 1, can be used. It turns out, that the most suitable ratio depends, among other things, on the embodiment is. In the case of a discontinuous embodiment, a somewhat lower acetonimine / acrylonitrile ratio can be used to obtain the same result content than in the case of a continuous embodiment. As can be seen, the temperature also has an influence. At a lower temperature can to obtain the same result with a lower acetone imine / Acrylonitrile ratio than at a higher temperature. The temperature Is preferably chosen between 50 and 145 C. Temperatures between 70 and 120 C. are particularly useful because within this area with one for practice suitable imine / acrylonitrile ratio, the highest possible yield of the desired Product can be achieved with a sufficient reaction rate.

The acetonimine to be reacted according to the invention can be prepared in a known manner made from acetone and a primary amine. There are different primary ones for this Suitable for amines. The acetonimine does not need to be obtained in pure form during production. The crude acetonimine can also be used. The acrylonitrile may also contain impurities such as acetonitrile. Upon request, the Acrylonitrile an inhibitor, e.g. hydroquinone, can be added. The presence of However, if possible, water in the reaction mixture should be restricted because Easily decompose acetonimine with water.

The process according to the invention can optionally be carried out in a solvent be performed. Suitable solvents are, for example, dimethyl sulfoxide, Benzene, toluene and benzonitrile. The reaction mixture can, if desired, a Catalyst, e.g. a quaternary ammonium base or another basic compound, be admitted. The amine from which the acetonimine is built also has a catalytic effect and is mostly present in small amounts in acetonimine.

The inventive method can be very advantageous at atmospheric Printing. However, other prints are also possible.

The mono- (2-cyanoethyl) acetonimine obtained according to the invention can with very high yield to S-oxocapronitrile (a very suitable starting material for the production of orPicolin) being hydrolyzed, the primary amine being from which the imine to be hydrolyzed is built up, can be recovered. The inventive Process thus offers the possibility of based on 5-oxocapronitrile the cheap raw materials acetone and acrylonitrile. For-such a her-

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Position of 5-oxocapronitrile can be various mono- (2-cyanoethyl) - 'ace'tdn'M "ine can be used as intermediates. For this purpose, however, N-cyelohexyl- (2-cyanoethyl) acetone jinine is preferred used because in the manufacture of this product from acrylonitrile and N-cyclohexylacetonimine - under the same conditions, by the way - a higher yield can be achieved than in the production of other mono- (2- cyanoethyl) -acetonimines. . .

The hydrolysis of mono- (2-cyanoethyl) acetoniraines can be very beneficial with dilute mineral acid, e.g. with sulfuric acid and hydrochloric acid. the The temperature can be varied during the hydrolysis. After hydrolysis it can 5-oxocapronitrile with a solvent such as ether, benzene and toluene from = the Hy-Ik drolysegemiseh can be extracted. A water phase then remains in which the amine formed during acid hydrolysis is dissolved as a salt. By addition The amine can be freed from e.g. dilute sodium hydroxide solution, after which it can be obtained by extraction. The amine thus obtained can then be used again for the Manufacture of acetonimine can be used.

The method according to the invention will now be described in more detail with the aid of a few examples explained; however, these are not intended to represent a limitation of the invention.

example 1

In a reaction vessel equipped with a stirrer and a reflux condenser of 1 liter content are 417 g of N-Cyclohexylacetonimin (3 mol) under atmospheric pressure Pressure heated up to 100 C. At this temperature within ^ 25 minutes 53 g of acrylonitrile (1 mol) were added with stirring. After adding the Acrylonitrile, stirring is continued at 100 ° C. for a further hour. Afterward the reaction mixture is subjected to fractional distillation. First will at a temperature of 77-78 C and at atmospheric pressure the unconverted Acrylonitrile (13 g) and then at 60 C and a pressure of 10 mm Hg that unconverted N-cyclohexyl acetonimine (321 g) distilled off. From the remaining 127 g of N-cyclohexyl- (2-cyanoethyl) -acetonimine are obtained by distillation (0.66 mol; boiling point 93-96 ° C at about 0.1 mm Hg) and 4 g of dicyanoethylated Product (boiling point 166-169 ° C at about 0.1 mm Hg) obtained.

The conversion of the acrylonitrile is 75%. From the used acrylonitrile 88% are in the monocyanoethylated product and only 4% in the dicyanoethylated Product has been implemented. The consumed Imixi is' au 95.5% to the raonocyanoäthyJ.ierten Product has been converted. '

45/1982

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Comparative example

In a reaction vessel equipped with a stirrer and a reflux condenser of 2 liters content are 695 g of N-Cyclohexylacetonimin (5 mol) under atmospheric pressure Pressure to 100 C heated. At this temperature within 25 minutes 265 g of acrylonitrile (5 mol) were added with stirring. After adding the acrylonitrile is stirred for 1 hour at 100 ° C., after which the reaction mixture subjected to fractional distillation. First be at a temperature from 76-78 C and at atmospheric pressure 47 g of acrylonitrile and then at 60 G and a pressure of 10 mm Hg. 281 g of N-cyclohexyl acetonimine distilled off. Off < 351 g of N-r-cyclohexyl- (2-cyanoethyl) -acetonimine are distilled to the remaining reaction product (1.83 mol; boiling point 92-94 ° C at about 0.1 mm Hg) and 265 g of dicyanoethylated product (1.08 mol; boiling point 170-174 ° C b, ei about 0.1 mm Hg).

Of the acrylonitrile consumed, 44.5% are in the monocyanoethylated Product and 52.5% have been converted into the dicyanoethylated product. The NMR analysis shows that the cyanoethyl groups in the dicyanoethylated product .instantly are bonded to the same carbon atom.

Example 2

115.2 g of N-cyclohexyl- (2-cyanoethyl) acetonimine, obtained according to Example 1, 700 ml of 1 η sulfuric acid are added at room temperature. The reaction mixture is then extracted with ether. From the resulting solution of 5-oxocapronitrile in ether, the ether is removed under reduced pressure. Of the The residue is distilled under reduced pressure. 65 g of 5-oxocapronitrile are obtained (Boiling point 63 C at about 0.7 mm Hg), which corresponds to a yield of 98%.

To the aqueous liquid remaining after extraction with ether 750 ml of 1 n sodium hydroxide solution are added, after which the mixture is extracted with benzene will. A solution of cyclohexylamine in benzene is obtained. This solution becomes 53 g of cyclohexylamine obtained by distillation, which corresponds to a yield of 90%. ,

Example .3

In a single reaction vessel equipped with a stirrer and a reflux condenser from 1 liter content 556 g of N-cyclohexyl acetonimine (4 mol) are at atmospheric Pressure heated up to 95 C. At this temperature, within 10

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Minutes 53 g of acrylonitrile (1 mol) were added with stirring, after which the stirring was continued 4 hours at 95 C is continued.

The reaction mixture is then fractionated. There will be no Acrylonitrile recovered. 420 g of unconverted N-cyclohexyl acetonimine are obtained and 182 g of N-cyclohexyl- (2-cyanoethyl) -acetonimine (0.95 mol; boiling point 92-94 ° C at about 0.1 mm Hg).

The yield, based on the original amount of acrylonitrile, is 95% and, based on N-cyclohexylacetonimine consumed, 97%.

Example 4

ρ In a reaction vessel equipped with a stirrer and a reflux condenser from 1 liter content 556 g of N-cyclohexyl acetonimine (4 mol) are at atmospheric Pressure heated to 85 C. At this temperature, 106 g of acrylonitrile (2 mol) are added with stirring over the course of 15 minutes, after which the stirring is continued 1.5 hours at 80-85 ° C is continued. The reaction mixture is then fractionated. First, at around 500 mm Hg and around 63-64 C, 42 g of acrylonitrile are and then distilled off at about 10 mm Hg and about 60 ° C. 389 g of N-cyclohexylacetonimine. 223 g of N-cyclohexyl- (2-cyanoethyl) -acetonimine are obtained from the remaining reaction product by distillation (1.16 mol; boiling point 91-92 C at about 0.1 mm Hg), which - based on acrylonitrile consumed - a yield of 96.5% and - based on N-Cyclohexylacetonimine consumed - a yield of about 97% ■ corresponds to.

Example 5

In a reaction vessel equipped with a stirrer and a reflux condenser from 1 liter content 495 g of N-isopropyl acetoneimine (5 mol) are obtained at atmospheric Pressure heated up to 80 C. At this temperature will be within 20 minutes 106 g of acrylonitrile (2 mol) were added with stirring; then another 1.5 hours at 80 ° C stirred. The reaction mixture is then subjected to a fractional distillation subjected. First, at about 500 mm Hg and about 63 C, there are 63 g of acrylonitrile and then at about 200 mm Hg and about 47 C 406 g of N-isopropylacetonimine a *> uestil.- " lates.

The remaining reaction product is converted into 108 by distillation

N-isopropyl- (2-cyanoethyl) -acetonimine (0.71 mol; boiling point 45-46 C at about 0.2- »si Hg) obtained, which - based on acrylonitrile consumed - a yield of &'■'. and - "based on N-isopropylacetonimine consumed - a yield of 73 %

speaks.

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■ 202 (3143

106.4 g of N-isopropyl- (2-eyanoethyl) -acetonimine are hydrolyzed in the same manner as in Example "2. 74.6 g of 5-oxocapronitrile are obtained," which corresponds to a yield of 96%.

Claims (11)

PATENT CLAIMS f \.) Process for the preparation of mono- (2-cyanoethyl) acetoniraines by reaction *** / of acrylonitrile with an acetonimine, characterized in that a ratio of at least 1.5 mol of acetonimine to 1 mol of acrylonitrile is used between the reactants and unconverted acetonimine is recovered from the resulting reaction mixture and, if desired, the reaction product mono- (2-cyanoethyl) acetonimine is hydrolyzed to 5-oxocapronitrile. 2. Process for the preparation of mono- (2-cyanoethyl) acetonimines by reaction of acrylonitrile with an acetonimine, characterized in that between the Reactants have a ratio of at least 1.5 moles of acetonimine to 1 mole Acrylonitrile used and unconverted from the resulting reaction mixture Acetonimine recovered w.rd. . * 3. The method according to claim 1 and 2, characterized in that "the reaction of Acrylonitrile is carried out with acetonimine at a temperature between 50 and 145 C. 4. The method according to claim 3, characterized in that the reaction takes place at a temperature between 70 and 120 ^° C. 5. The method according to any one of claims 1-4, characterized in that the acrylonitrile is only partially converted, non-converted from the reaction mixture obtained Acrylonitrile is recovered and the temperature of the reaction mixture is kept above 50 ° C. until the acrylonitrile is precipitated. 6. The method according to any one of claims 1-5, characterized in that the reaction takes place at atmospheric pressure. 7. The method according to any one of claims 1-6, characterized in that the acetonimine N-Cyclohexylacetonimine is used. , · 8. A process for the preparation of 5-oxocapronitrile, characterized in that a mono- (2-cyanoethyl) acetoneimine, obtained using the process '"' according to any one of claims 1-7, subjected to hydrolysis. 9 »The method of claim 8, characterized in that one carries out the hydrolysis with dilute mineral acid, from the resulting Hydroiysegerolsch the * gefeil- '" detention 5-Öxocapronitri j extracted with a solvent.' Üiiü ¹ of ^ the · -isvirSck "- "'- ^ permanent aqueous solution formed during hydrolysis" öte ^; '' Amin "'" gWihh ^{; i:} " ^'1'""■■'■' 009845/1982 * ^ ^! ^ BATH ORIGINAL 2020H3 10. Mono- (2-cyanoethyl) acetonimine, obtained using the method according to any of claims 1-7. 11. 5-oxocapronitrile, obtained using the method according to one of the claims 1, 8 and 9. 009845/1982 BATH