DE2106650A1 - Process for the production of acetoacetamide - Google Patents

Description

Process for the production of acetoacetamide

It is "known to produce acetoacetamide from ammonia and diketene, the process being carried out in the gas phase being described in DAS A 112 510. The problem of dissipating the heat of reaction is solved in this package by using an inert gas, e.g. Nitrogen is used as a diluent In Example 1, a throughput of 0.1 g Hol 500 liters of nitrogen are required, which means that this process is not particularly suitable.

On the other hand, it is more advantageous to work in an aqueous solution that is as concentrated as possible. So will the procedure the Swiss patent 287 558 the implementation of diketene with ammonium carbonate in aqueous solution. The disadvantages of this method are However, the relatively high price of ammonium carbonate and the evolution of carbon dioxide that takes place. which makes continuous work very difficult, if not prevented at all «. ·

It is also known that concentrated, aqueous Acetoacetamide solutions can be prepared by

one water, ammonia and diketene in an aqueous acetoacetate amide solution with the same acetoacetamide content

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how the solution to be produced is introduced and the heat dissipated by cooling (DAS 1 125 418). There pure Acetoacetamide is hygroscopic, separating the water from these solutions requires quite a bit technical effort. The difficulties are also increased by the heat sensitivity of acetoacetamide.

Finally, the reaction was also carried out in inert, organic solvents (ether, benzene). Because of the poor solubility of acetoacetamide in these media, large amounts of solvent are used in this case necessary. In addition, by-products are formed, in particular S ^ -dihydroxy-G-methyl-J-acetyl-pyridine (Houben-Weyl 714 Georg Thieme Verlag, Stuttgart, 1968, S..253), the separation of which is at least one additional Yerfahrenschdtt (TJmkristallisati <? Ji), - requires.

The present invention relates to a method ~ for the continuous production of acetoacetamide in the liquid phase from diketene and ammonia, which has these disadvantages eliminated. The method is characterized in that methanol, ethanol or chlorinated hydrocarbons are used as solvents with boiling points between 12 and 80 ° C, preferably 40 to 65 ° C are used, the reaction carried out at 10 to 80 ° C, preferably between 20 ° and 60 ° C and the reaction product continuously from the reaction components is separated.

It can all be suitable for continuous mode Apparatus are used with the measure that in the case of using methanol or ethanol as a solvent the dwell time must not exceed 2 hours. On the other hand, when using chlorinated hydrocarbons the dwell time is a maximum of 10 minutes.

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Acetoacetamide is completely or partially from the solvent separated and the mother liquor wholly or partially circulated together with the solvent.

As chlorinated hydrocarbons, for example, ethyl chloride, chloroform, carbon tetrachloride, dichloroethylene, especially methylene hybrid can be used.

For carrying out the reaction, equipment suitable for the continuous mode, such as, for. B. vessels equipped with overflows, reaction tubes, towers and circulation equipment, preferably falling film or thin-film evaporators, whose heating is replaced by cooling.

The acetoacetamide can be separated off by cooling the Solution and subsequent filtration take place. If necessary, some of the solvent is previously removed by distillation removed.

The inventive method has compared to the previously known the following advantages:

1. The solvents used can be separated from the acetoacetamide produced without high expenditure of energy. Included the time-consuming drying of the resulting reaction product is no longer necessary.

2. The circulation process means that there are only small amounts of solvent necessary.

3 »The product is pure and in high yield. Subsequent cleaning is not necessary.

4. Normal cooling water is sufficient to dissipate the heat of reaction. If necessary, it can also be caused by condensation of the evaporating solvent can be removed.

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5. Me formation of by-products eg 2,4-dihydroxy-6-methyl-3-acetyl-pyridine, but also ß-aminocrotonic acid amide, 4-amino-6-oxo-2,4-dimethyl-1,4,5 » 6-tetrahydropyridine-3-carboxamide, 6-0xo-2,4-dimethyl-i, 6-dihydropyridine-3-carboxamide and 3- (3-imino-buten-2-oylamino) buten-2-acid amide (CH ₅ -C = CH-CO-HH ₂ "becomes almost

()) completely prevented.

Mketene reacts much more quickly with methanol and ethanol than with water. It is therefore surprising that acetoacetamide can be produced in methanolic and ethanolic solutions leaves. This is especially the case because basic compounds cause acetoacetic ester formation strongly catalyze. When carrying out the process, the mother liquor, which is often reused, could also be found no methyl acetoacetate (not even by gas chromatography) be detected.

Furthermore, it was by no means to be foreseen that with the short residence times in falling-film or thin-film evaporators the Reaction proceeds quantitatively.

Reaction is carried out without a solvent using the same Reaktioneapparaturen and reaction temperatures, one obtains a product with a melting point of about 46 ° C to 15O ⁰ C, often about 3OO ⁰ C-

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example Λ

A solution was put into a thin-film evaporator, the upper third of which was equipped with water cooling of 84 g of diketene in 100 ml of methylene chloride and 17 g of ammonia are metered in from above in cocurrent. The throughput was 2 mol / h, the temperature in the gas space was 4 cm above the wiper blades 31-33 C.

The reaction solution flowed into an intermediate container where it was cooled to 15 ° C. The majority of the Acetoacetamids in the form of white crystals.

After suctioning off, a starting solution with the same diketene concentration was prepared from 70% of the mother liquor, diketene and methylene chloride and reacted with ammonia as above. This procedure was repeated several times. The acetoacetamide produced was entirely white, the melting point was 51 - 53 ° C.

About 80% of the methylene chloride was distilled off from the mother liquor which had been branched off, and the crystals which had precipitated were filtered off with suction and washed with a little cold methylene chloride. The acetoacetamide was dried with nitrogen at room temperature, - ^ _x

Total yield of pure product: 96 %

Example 2

The experiment was repeated in the same apparatus with half the amount of methylene chloride (50 ml per 84 g of diketene). The temperature in the gas space of the reactor was 38-40 ° C

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In an analogous work-up, a pure, white Acetoacet.amid was obtained obtained in a yield of 97%, based on ammonia and diketene.

Example 3

As described in Example 1, a solution of 168 g of diketene in 1000 ml of carbon tetrachloride was reacted with 54 g of ammonia within one hour. The temperature in the gas space was kept at 45.degree. When the reaction solution was cooled, the acetoacetamide precipitated out as a white crystalline mass. A 2nd fraction was obtained by concentrating the cutter liquor. The drying was done at room temperature with nitrogen.

Yield of pure acetoacetamide: 93% <■

Example 4

In the same way as in Example 1, a solution of 84 g of diketene in 100 ml of methanol was reacted. The reaction solution was concentrated and cooled, and the acetoacetamide formed was filtered off with suction. In each case 70 % of the mother liquor were circulated analogously to Example 1. The discharged mother liquor was collected and worked up as described in Example 1. The acetoacetamide obtained was dried at 30 ° -35 ° in a stream of nitrogen.

Total yield of pure acetoacetamide: 95 % 51-52.5

5 °

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Example 5

The same experiment was carried out as in Example Λ with a third of the amount of solvent and a gas space temperature of 50 ° G repeated.

Total yield of pure, white acetoacetamide: 96 % Pp: 51 - 52.5 ° C.

Example 6

This experiment was carried out as in Example 1 with 80 ml of methanol, Oe 84 g of Diket «
carried out.

Oe 84 g of diketene and a gas space temperature of 40 - 42 ° C

Total yield of pure, white acetoacetamide: 95 % : 52 - 53 ° C.

Example 7 '

The use of ethanol as a solvent (80 ml per 84 g of diketene) led to a yield of pure, white acetoacetamide of 96% at the same gas space temperature as in Example 6 and with the same reaction procedure and work-up.
Mp: 51.5 - 53 ° C.

Comparative example:

The experiment Λ was carried out without a solvent, but otherwise in a completely analogous manner. The yield of a yellow crystalline substance was 94%. The melting point was 48-125 ° C ..

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Claims (6)

Claims / 1.) / Process for the continuous production of aceto / Acetamide in the liquid phase from diketene and ammonia, characterized in that methanol, ethanol or chlorinated hydrocarbons are used with boiling points between 12 and 80 ° C and the reaction is carried out at 10 to 80 ° C and the Eeaktionsprodukt continuously from the Ee akti ons components is separated. 2.) Method according to claim 1, characterized in that
, is carried out. shows that the reaction is between 20 and 60 ° C 3.) Process according to claims 1 and 2, characterized in that such as chlorinated hydrocarbons
be used. substances those with boiling points between 40 ° and 65 ° 4.) Process according to claims 1 to 3 * thereby characterized in that methylene chloride is used as the solvent. 5.) Process according to claims 1 to 4, characterized characterized in that "the reaction in a falling-film or thin-film evaporator, its heating is replaced by cooling. 6.) Process according to claims 1 to 5, characterized in that acetoacetamide is whole or partly separated from the solvent and the mother liquor wholly or partly with the solvent is circulated. 209838/1189