NL8100623A - PROCESS FOR PREPARING DI-N-PROPYLACACIC ACID. - Google Patents

Description

Process for preparing di-n-propyl acetic acid.

Dutch patent application 77.05564 describes a process for preparing di-n-propylacetic acid to form di-n-propylacetonitrile as an intermediate. The di-n-propylacetonitrile is then converted to di-n-propyl acetic acid by hydrolysis with 75-80% sulfuric acid at a temperature of 80-140 ° C, after which the crude di-n-propylacelamide formed is diazotized with sodium nitrite in 75-80% sulfuric acid at a temperature of 40-80 ° C. These steps are shown in reaction scheme A.

There are various drawbacks to this conversion of di-n-p & pylacetonitrile to di-n-propyl acetic acid. For example, sodium nitrite is a relatively toxic compound (LD 1 for rats when administered orally 180 mg / kg) and gives rise to contamination of di-n-propyl acetic acid with nitrite and nitrate 15 ions. Another source of contamination is valeronitrile, which is present as an impurity in the di-n-propylacetonitrile and which produces valeric acid during treatment which imparts an unpleasant odor to the di-n-propyl acetic acid. In addition, the use of concentrated sulfuric acid reduces the yield as well as the efficiency of the treatment.

According to the invention, di-n-propylacetonitrile is converted to di-n-propylacetic acid without using sodium nitrite by reducing the sulfuric acid concentration to 55-65% and refluxing after the hydrolysis of di-n-propylacetonitrile. di-n-propyl acetamide is hydrolyzed to di-n-propyl acetic acid.

In carrying out the process according to the invention, di-n-propylacetonitrile is hydrolyzed in concentrated sulfuric acid, after which water is added to the reaction mixture to a sulfuric acid concentration of 55-65% and preferably 60% and heating is continued under reflux, preferably about 4-6 hours at about 125-128 ° C. The yield of di-n-propylacetic acid is increased to 9 & 1 by a factor of 2.5 compared to the conversion according to the above-mentioned Dutch patent application 77.0556¾, whereby a yield of up to 92% is obtained. The conversion of di-n-propylacet-5 amide to di-n-propyl acetic acid is shown in reaction scheme B.

It has furthermore been found that the di-n-propyl acetic acid can be liberated largely from valeric acid by steam treatment, which is moreover more efficient than distillation as according to the aforementioned Dutch patent application 77.0556¾. The following tests show that about 50% of valeric acid can be removed from di-n-propyl acetic acid by steam treatment.

Di-n-propylacetonitrile according to the invention was hydrolyzed in 60% sulfuric acid. The reaction mixture contained 15 grams (1 mole) of di-n-propyl acetic acid, 730 grams of 60% sulfuric acid, and 0.35 weight percent valeric acid. The reaction mixture was divided into several portions to which valeric acid was added to a concentration of 1% by weight. The mixtures were then treated with a steam jet keeping the volume constant and the temperature kept at 130 ° C. The amount of water required for the separation was 1800 ml per mole of separated product.

After decanting at room temperature, it was dried over anhydrous sodium sulfate. The yield of di-n-propyl acetic acid was practically quantitative. The amount of valeric acid remaining is shown in Table A below.

Table A

test 30 1 2 3 35 ¾ amount of added valeric acid, wt. $ 0.35 ο, βο 0.80 1.00 amount of residual valeric acid, wt. $ 0.2 0.3 0, ¾ 0.5 81 00 62 3 3

The mixture containing 1 wt% valeric acid (1.1 * 1 * gr.) Was also continuously steam-treated, collecting 1 * different fractions successively. The amount of valeric acid in each fraction is shown in Table 5 below.

Table B

10 15 fraction weight of amount left behind each fraction, g acid, gram wt.% 1 3 6 0.32U 0.9 2 3 ^ 0.204 0.6 3 1 * 2 0.081 * 0.2 1 * 32 0.032 0.1 total I 0.61 * 1 * the amount of valeric acid recovered was: kk, J2%.

As already mentioned, rat results in Tables A and B show that by steam treatment the valeric acid content in the di-n-propyl acetic acid is reduced by about 50%. Thus, the di-n-propyl acetic acid is largely deprived of the malodorous odor of valeric acid.

^ Example I.

72 g were placed in a 1-liter flask fitted with a stirrer, thermometer, dropping funnel and reflux condenser. distilled water and then slowly stirring 1 * 78 gr. 92% sulfuric acid at which the temperature was not allowed to rise above 60 ° C. After this, 125.2 gr. (1 mol) di-n-propyl ethonitrile added once and the temperature was brought to 100 ° C. After 1 hour at this temperature, the di-n-propylacetonitrile was almost completely hydrolyzed to di-n-propylacetamide. 185 g. Was added to the reaction mixture. distilled water added all at once 35 81 00 62 3 k at which the sulfuric acid concentration dropped to 6%. The mixture was then heated at reflux at 125-130 ° C for 5 hours. Afterwards, the dropping funnel was replaced with an introduction tube below the liquid surface, and the reflux condenser with a distillation attachment. In the reaction mixture, steam was introduced with an intermediate discharge of water to keep the volume constant and thereby promote efficiency and hydrolysis.

After 2.5 hours two phases had formed and separated well. The amount of water that had been required for the separation was 1750 grams. The organic phase was dried azSotropically under reduced pressure (20 mm mercury, 20 ° C.). Thus, 138.5 gr. di-n-propyl acetic acid (96.2% yield), which could be further purified by evaporation.

Example II.

Into an enamelled reactor equipped with a 200 liter flask, reflux temperature, stirrer and bottom stopper, 0.657 kg of distilled water was introduced with supply to the flask of steam under a pressure of about 600 kPa (620 kg / cm) and water. While the temperature was kept at 50 DEG-60 DEG C., 2.085 L (3.753 kg) of 9-sulfuric acid was added with stirring, * 4 "

After stirring for 15 minutes, the concentration was checked to be 80-1 wt% as required, and the temperature was brought to 100 ° C. A. amount of 1 kg. di-n-propylacetonitrile was added while maintaining the temperature at 100 ° C (exothermic reaction) and stirring at this temperature for 1 hour.

Afterwards, 1.70 kg. distilled water was added while maintaining the temperature by gentle heating at which the sulfuric acid concentration dropped to 60%. The mixture was then heated at reflux at 125-128 ° C for 6 hours.

Afterwards, the reaction mixture was cooled to about 30 ° C and the stirring was stopped. After standing for 30 minutes, the bottom layer (3.5 liters or about 5 kg, sulfuric acid concentration about 39%) was removed. The organic layer was washed with 1.333 kg for about 30 minutes. distilled water at 8 1 0 0 62 3 5 about 30 ° C. After standing for another 30 minutes, the bottom aqueous layer (11lt kg.) Was removed. The organic phase was dried to a content of about. Thus, 1.12 kg. di-n-propyl acetic acid (97-98 # yield).

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Claims (8)

1. Process for preparing di-n-propyl acetic acid from di-n-propylacetamide, characterized in that di-n-propylacetamide is hydrolyzed with 55-65% sulfuric acid with heating. A method according to claim 1, characterized in. that di-n-propylacetamide is hydrolyzed with 60% sulfuric acid. * 3. Process according to claim 1 or 2, characterized in that di-n-propylacetamide is hydrolyzed for 6 hours. k. Process according to any one of the preceding claims, characterized in that the hydrolysis is carried out under reflux. 5. Process according to any one of the preceding claims, characterized in that the di-n-propylacetamide originates from the hydrolysis of di-n-propylacetonitrile. 6. Process according to claim 5, characterized in that the reaction mixture from the hydrolysis of di-n-propyl-acetonitrile with water is brought to a sulfuric acid concentration of 55-65%, after which the mixture is heated. Process according to claim 6, characterized in that the mixture is heated under reflux for 6 hours. 8. Process according to any one of the preceding claims, characterized in that the di-n-propyl acetic acid is purified by steam treatment. The process according to any one of claims 1 to 8, characterized in that the reaction mixture from the hydrolysis of di-n-propyl acetamide is treated with steam to separate di-n-propyl acetic acid. 10. Methods as described in the description and examples. 81 00 62 3 -A. n. C, H? '' CH-C: N / H ^ O · 'H * 8Q ° / «η-εΛ n.CjH? \ n-c /? CH-C-NH + NaNO * H SO, λ A A ** Π - \ π-C ^ CH_ C-OH + Ν,> HO + Na Η S Οι Λ λ ^ Β_ n-ClH? χ- ν - η-Ο, Η, ο It 'λ Η ^ Ο nC. ^ Ο II CH- C-NHj HS0 A- -4 (60 ° / ») nC ^ ✓ CH - C- OH 4 <NH) SO, 4 A 4 OMNIUM FINANCIER AQUITAINE POUR L'HYGIENE ET LA SANTÉ (SANOFI), Courbevoie, France 81 0 0 62 3