DEK0013745MA - - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

Registration date: April 2, 1952. Advertised June 21, 1956

GERMAN PATENT OFFICE

It is known that the nitriles of yS-ketocarboxylic acids, especially those of a purely aliphatic nature, very prone to polymerization, such as z. B. the nitrile of acetoacetic acid, which can only be kept for a short time. Likewise, for example isobutyrylacetonitrile ascribed only a moderate shelf life (E. H. Kroeker and S. M. Mc. Elvain, Journal of American Chemical Society, Vol. 56, p. 1171 [1934]). It colors turns dark when stored and will polymerize after a while. These polymerization processes are exothermic and can even run explosively under certain circumstances. Naturally, the Polymerization accelerated by heating, so that just higher molecular weight aliphatic ^ -Ketocarbonsäurenitrile are particularly at risk when cleaning by vacuum distillation. This Polymerization is mainly catalyzed by the presence of alkali, including traces, as is sometimes the case from glass vessels are sufficient.

It has now been found that relatively minor additions of acid chlorides, such as. B. acetyl chloride or thionyl chloride, or of chlorides of phosphorus, such as P Cl ₃ or P Cl ₅ and POCl ₃ , completely inhibit this polymerization, and in addition, the inhibiting effect is also retained in the distillate when the crude nitrile stabilized with such chlorides in the Vacuum of the water jet pump or in a high vacuum is cleaned.

609 5W485

Claims (2)

K 13745 IVb / 12 ο This inhibiting effect after the distillation also occurs when the boiling point of the acid chloride added is relatively far apart from the boiling point of the nitrile. So shows z. B. the butyrylacetonitrile has a boiling point of 85 to 90 ⁰ at 2 mm pressure and the SO Cl _{2 is} known to have a pressure of 78.8 ° at 760 mm. Under such conditions, after fractionation in a high vacuum in pure butyrylacetonitrile, practically no more SO Cl ₂ is to be expected, but it has now proven to be very storable. In this way, raw butyrylacetonitrile or unstabilized butyrylacetonitrile that has been purified in a high vacuum polymerizes in the presence of amphoteric metals, such as. B. Aluminum, at 60 to 80 ° in a few hours, while that pretreated with acid chlorides Nitrile does not change in the slightest after 72 hours at 60 to 80 °. ao example. The Z. B. Levine and Hauser ("Journal of American Chemical Society", vol. 68, p. 760 [1946]) produced butyrylacetonitrile, which is in an ethereal or benzene solution at the end of the reaction, is after brief drying over sodium sulfate with about ι ecm SOCl _{2 added} per mole and left to stand for 24 hours. After this time. has. a slight viscous, dark substance secreted ^r off, which may be of poured off without filtration. After the solvent has evaporated, the mixture is fractionated in vacuo and the ^{butylacetonitrile which passes over between 85 and 90 °} at 2 mm is distilled over without a polymerization residue remaining in the distillation flask. The nitrile obtained proves to be absolutely storable. U.S. Patent 2,143,941 is the Stabilization of unsaturated compounds, especially acrylic acid and its derivatives, described by adding small amounts of anhydrous metal halides. In the German patent Scripture 811 952 also states that cyanohydrins (α-Oxynitrile) by adding acids medium strength or optionally of acid chlorides, which under the circumstances of the reaction such acids can be stabilized. Both patents require that the Stabilizers have approximately the same boiling point as the substance to be stabilized. In contrast, the present invention is a completely different group of substances, the aliphatic ^ -Ketocarbonsäurenitrile, whose polymerization takes place according to a completely different scheme, namely by elimination of water between the CO group of a molecule ^ and the activated by the neighboring groups CH ₂ group of another molecule, while the polymerization "of the a-oxyriifrile is preceded by cleavage into aldehydes and hydrocyanic acid, and the polymerization of the unsaturated compounds according to the process of US Pat. No. 2,143,941 on the known addition reactions In further contrast to the processes of the patents mentioned, it is also not necessary according to the present invention to use a stabilizer whose boiling point is close to the boiling point of the substance to be stabilized. ... .''...'... V ... PATENT CLAIMS: i: method of stabilizing aliphatic / J-ketocarboxylic acid nitriles, characterized in that that small amounts of acid chlorides are added to them. 2. The method according to claim 1, characterized in that one is used as a stabilizing Active additives including acetyl chloride, thionyl chloride or the chlorides of phosphorus Phosphorus oxychloride used. Dressed Dfütksohriftein:
.German Patent No. 811952;
U.S. Patent No. 2,143,941.