DE1086683B - Process for the preparation of 1-acyloxy-1,1-dicyanaethanes - Google Patents

Description

Process for the preparation of 1-acyloxy-1, 1-dicyanethanes The invention relates to a process for the manufacture. treatment of 1-acyloxy-1, 1-dicyanethanes through Reaction of an excess of an anhydride of a saturated fatty acid with 2 up to 4 carbon atoms with hydrogen cyanide in the liquid phase and in the presence a tertiary amine as a catalyst.

1-acyloxy-1, 1-dicyanethane and in particular 1-acetoxy-1, l-dicyanethane are of considerable technical importance because they form monomeric vinylidenecyanide or its homologues can be pyrolyzed, which in turn are of great value for the manufacture of synthetic resins are specially designed for manufacture excellent threads and films serve. The pyrolysis of 1-acetoxy-1, 1-dicyanethane with the formation of monomeric vinylidenecyanide is described in U.S. Pat. No. 2,476,270 described.

It is known from US Pat. No. 2,623,062 that acetic anhydride and hydrogen cyanide in the liquid phase in the presence of basic catalysts Formation of 1-acetoxy-1, 1-dicyanethane react. As such are catalysts both organic and inorganic substances, e.g. B. tertiary amines such as trimethylamine, Triethylamine. Tributylamine, hexamethylenetetramine, pyridine and the like, alkali salts of organic Monocarboxylic acids, e.g. B. sodium acetate, sodium propionate, sodium butyrate, potassium acetate and the like, secondary amines, such as dimethylamine, diethylamine, diisopropylamine and the like, as well as other organic and inorganic bases, e.g. B. Sodium Hydroxide, Potassium Hydroxide, Ammonium hydroxide, quaternary ammonium bases and the like have been proposed.

In general, 1-acetoxy-1, 1-dicyanethane is definitely used obtained in good yield. But when using these alkaline catalysts there are also more or less large amounts of tarry components, which are not only reduce the yield of the desired acyloxydinitrile, but also extremely are difficult to remove from the reaction system, thus causing clogging, affect the heat transfer in the unfavorable sense and through shutdowns for the purpose Removing the residue and cleaning the device is a significant loss of time cause.

According to the invention now becomes a more effective and economical one Process for the preparation of 1-acyloxy-1, 1-dicyanathans proposed that dadruch is characterized in that one uses α-, ß- or # -Picolin as a catalyst, Under these process conditions, tarry residues arise only to a negligible extent small amount.

The reaction of carboxylic anhydrides with hydrogen cyanide in the presence a catalytic amount of an α-, ß- or # -picolins proceeds according to the general Equation 2R-CO-0-CO-R + 2. HCN-oRCOOC (CN) 2-R + 2RCOOH in each of which R is a saturated one Means hydrocarbon radical with 2 to 4 carbon atoms.

0.01 to 5 percent by weight, based on picoline, is preferred the amount of reactants used.

The temperature at which the reaction is carried out is of none special meaning and can vary within wide limits. But when. Acetic anhydride is applied in the liquid phase at a temperature above about 100 ° C, becomes easy Acetamide and diacetimide are also formed and thereby the yield of the desired Acyloxynitrile somewhat reduced. When carrying out the implementation in liquid Phase it is therefore particularly desirable to have a reaction temperature below about 100 ° C and especially in the range between 10 and 70 ° C. But it can also Temperatures below 10 ° C can be used with success. Indeed, it will be excellent Yields of Acyloxydicyanäthanen even at temperatures down to -70 ° C and get even deeper. However, considerably longer reaction times are required can be applied.

As can be seen from the above reaction equation, are stoichiometric 2 moles of carboxylic anhydride and 2 moles of hydrogen cyanide are required for the reaction to take place can take place. But it can also be one of the two reactants in stoichiometric Excess can be applied. Optimal yields of the desired product will be received when an excess of the carboxylic anhydride, e.g. B. 1, 2 to 4 moles per mole of hydrogen cyanide are used.

The catalyst to be used in the present invention can be one of the three known picolines, i.e. a-picoline (2-methylpyridine), ß-picolin- (3-methylpyridine) or γ-picoline (4-methylpyridine). These isomeric picolines are liquids which are soluble in liquid carboxylic acid anhydrides and therefore simply in the anhydride can be dissolved with hydrogen cyanide before its unisition # -Pricolins are the acycloxydicyanethanes in the highest yield with the lowest Residues received, which is why it is particularly preferred.-But also with the a-and good results are obtained for the B isomer. Mixtures can of course also be used the Picoline can be applied.

The reaction itself can be carried out in the most varied of ways will. You can z. B. first the catalyst in the liquid carboxylic acid anhydride dissolve and then introduce gaseous hydrogen cyanide into the mixture, which by external Cooling, which is necessary because the reaction is exothermic, to the desired level Temperature is maintained. This procedure is advantageous because the gradual addition of hydrogen cyanide less heat is developed and the temperature is increased can be easily regulated. The way of working is in no way decisive Meaning. If appropriate, the total amount of reactants and catalyst can be used mix together at the same time. Another way of doing this is: First mix the carboxylic anhydride, the Hydrogen cyanide and the catalyst in a closed vessel to then push the mixture through a tube that is kept at the required temperature and in which the reaction takes place. Diesel's process only requires a very short reaction time (20 to 30 minutes) and gives very high yields of the acyloxydicyanethane concerned. The reaction but can also in the presence of inert solvents or diluents, eg. B. of benzene, Nitrobenzene, dioxane and the like.

After completion of the implementation, i. H. after the heat development has ceased, the catalyst is best neutralized with an acidic substance and the acyloxydicyanethane from the reaction mixture, which also has not yet reacted hydrogen cyanide and carboxylic acid anhydride may contain, by simple distillation, preferably under reduced pressure, or separated and recovered in another known manner.

The following examples serve to explain the design according to the invention in more detail Procedure.

Examples 1 to 17 By reacting acetic anhydride with hydrogen cyanide in the liquid phase in the presence of a number of basic catalysts including picoline, 1-acetoxy-1,1-dicyanethane is prepared using various temperatures and molar proportions of the reactants. All essential information is compiled in the following table. Carbon Re- catalyst acidic HCN alktons temperature yield residue Example Katlaysator Weight anhydride time percent (mole) (mole) (hours) (° C) (%) (%) 1 0.01 3.5 1 72 40 92.5 5.8 2 # picoline ............................... 0.01 3.5 1 96 35 97 3.7 3 # picoline ............................... 0.01 3.5 1 21.5 60 91.6 9 , 2 4 # picoline ............................... 0.008 1.6 0.722 0.5 100 91.3 7.4 5 # picoline ............................... 0.006 3.4 1 14 100 91.3 7.4 6 # picoline ............................... 0.01 3.5 1 96 20 96 8.6 7 # -Picolin .............................. 0.01 3.5 1 100 -70 97 3, 7 8 # picoline .............................. 0.01 2.0 1 96 -70 90 5.5 9 0, 013, 513707010 10 0.01 2.0 1 6 91 58 30 11 potassium cyanide ........................... 0.01 2.0 1 6 60 59.8 50.5 12 triethylamine ........................... 0.02 2.0 1 3 70 58.4 39.2 13 hexamethylenetetramine ................... 0.01 3.5 1 3 70 0 0 14 Potassium acetate 0, 01 3, 5 1 2, 5 70 to 85 58, 1 38, 2 15 dimethylethanolamine .................... 0.016 1.6 0.73 3.5 70 75.1 41.1 16 2,4-dimethylpyridine .................... 0.008 1.6 0.74 3.5 70 51.9 18.4 17 N, N-diethylcyclohenxylamine 0.01 1.8 0.558 3.0 10 61.3 79, 1 When α-picoline was used instead of β- or γ-picoline in Examples 1 to 9, excellent results were also obtained.

In practically the same manner as indicated above, were performed the following examples.

Example 18 A mixture of 240 g of acetic anhydride of 99.5% strength Purity, 27 g of hydrogen cyanide and 0.93 g, -picoline was in a closed Vessel heated to 70 ° C. under pressure in the liquid phase for 3 hours.

The reaction mixture was then cooled and at 110 to 120 ° C / 15 distilled up to 20 mm. The yield of 1-acetoxy-1,1-dicyanethane was 45 g. It remained a distillation residue of 2.1 g, corresponding to 4.7 percent by weight, based on 1-acetoxy-1, 1-dicyanethane.

In a comparative experiment, 205 g of acetic anhydride of 99, 5% purity, 27.4g hydrogen cyanide and 2.4 ccm of a 25 percent by weight aqueous solution of trimethylamine mixed homogeneously. When the closed reaction vessel Heated to 70 ° C. for 3 hours, the mixture cooled and then distilled as above 44.8 g of dinitrile were obtained, while 5.4 g of tarry distillation nitrogen was obtained remained, which, based on the 1-acetoxy-1, 1-dicyanethane, corresponded to 12.2%.

Example 19 A mixture of 2 moles of propionic anhydride and 1 mole Hydrogen cyanide was in the presence of 0.015 moles of γ-picoline per mole of hydrogen cyanide Heated to 75 ° C for 2½ hours. The reaction mixture contained 3.5% free hydrogen cyanide and 15.4% bound CN, as determined by a modified Volhard titration became. The yield of 1 n-propoxy-1,1-dicyanethane was 820 / o of theory. Of the residue remaining in the vacuum distillation of n-propoxy-1, 1-dicyanoethane was 1.3 percent by weight, based on the dinitrile. The n-propoxy-1, 1-dicyanathan had a melting point of 57.5 ° C. after recrystallization.

Example 20 A mixture of 2 moles of n-butyric anhydride and 1 mole Hydrogen cyanide was 21/2 in the presence of 0.015 mol of y-picoline per mol of hydrogen cyanide Heated to 75 ° C for hours. The crude reaction product contained after vacuum distillation 3.98% free HCN and 10.3 I / o bound C N. The yield of 1 n-butoxy-1, 1-dicyanethane was 75.5% of theory; the distillation residue after distillation was 0.85 percent by weight. The crude 1 n-butoxy-1, 1-dicyanethane was at room temperature fluid.

It is clear from the examples that the Picoline is different basic substances as catalysts for the implementation of carboxylic anhydrides with Hydrogen cyanide are greatly superior in that they are extraordinarily useful in their use high yields and only very small amounts of residues can be obtained.

Except as intermediates for the production of polymerizable monomers Substances are the acyloxydicyanethanes produced by the process according to the invention also valuable for other purposes. So they have z. B. insecticide, fungicide and herbicidal properties.

Claims (3)

PATENT CLAIMS: 1. Process for the preparation of 1-acyloxy-1, 1-dicyanethanes by reacting an excess of an anhydride of a saturated fatty acid with 2 to 4 carbon atoms with hydrogen cyanide in the liquid phase and in the presence a tertiary amine as a catalyst, characterized in that a-, B or y-picoline used as a catalyst. 2. The method according to claim 1, characterized in that 0, 01 to 5 percent by weight of y-picoline, based on the amount of reactants used, used. 3. The method according to claim 1 or 2, characterized in that reacting acetic anhydride with hydrogen cyanide. Considered publications: German Patent Specifications No. 809911, 888243.