DE646482C - Process for the preparation of 1,3-glycol half-esters - Google Patents

Description

Process for the production of 1, 3-glycol half-esters It is known that from aldehydes which have a methyl group in a-position to the carbonyl group, when exposed to alkaline condensation agents "r, 3-glycol half-esters can produce. The formation of these esters can be explained by the fact that 2 Molecules. Aldehyde react with 'aldol formation and that this aldol is with a another molecule of aldehyde corresponding to the Cannizaro's reaction under formation of a r, 3-glycol half ester.

The - implementation probably takes place according to the following equation: Alcoholic potassium hydroxide, sodium acetate, sodium ethylate and milk of lime can be used as condensation agents. However, the yields of half-esters are very poor, and a large number of undesired by-products are formed, such as aldols, lower molecular weight esters and glycols formed by saponification.

The condensation can be carried out on a laboratory scale with somewhat better success in Perform the presence of metallic sodium. The usage however, metallic sodium as a condensing agent comes across during processing larger amounts of aldehydes on difficulty. The condensation then takes place namely so suddenly and has such a sudden sharp rise in temperature As a result, even very strong cooling cannot dissipate the heat. Through this the condensation preferably proceeds with the formation of low-boiling products, especially low-boiling esters, and there are sensitive losses in yield.

The condensation is much milder when using solvents. However, this is shaped by the processing of the larger amounts of liquid Procedure very cumbersome.

It has now been found that with very good yields and in technical simply from aliphatic aldehydes in the 2-position to the carbonyl group are substituted by alkyl groups, with the help of alkaline isolating agents i, 3-glycol half esters can be produced if the condensation agent used is solid caustic alkalis or N atriuniainid or mixtures of these substances are used. The condensation proceeds in this case completely evenly, and the reaction will last for a longer period of time extended. This means that the heat of reaction can be evenly distributed even with large batches dissipated and a constant temperature maintained.

The condensation must be carried out at temperatures below 100 °, because otherwise there will be significant losses in the yield of half-esters. The best Yields of half esters, about 90 ° 10, are achieved when the condensation is at room temperature or little about it.

The condensation can be carried out in stirred kettles equipped with effective cooling equipment. It is more advantageous to spread the condensation agent on trays, repeatedly pass the aldehyde over it and then cool it thoroughly each time. The consumption of condensing agent is on average 3 to -1010 of the amount of aldehyde used.

To work up the condensation product, it is acidified with hydrochloric acid, Washed neutral with water and with steam of unchanged aldehyde and minor Quantities of low-boiling products are distilled. You can also do the prelims with ordinary Separate pressure or weak negative pressure. The half ester is then reduced under Distilled pressure. the purer the starting aldehyde, the more colorless it is obtained half-ester. Strongly colored half-esters can be caused by subsequent, borrowed, cautious, catalytic treatment with hydrogen can be decolorized. The arrears always do only a few percent off. By X 'saponification of the half-ester, the corresponding i, 3-glycols and acids are easily obtained.

All aliphatic aldehydes that are present in 2-position to the carbonyl group are substituted by alkyl groups, process, z. B. 2-methylpropanal- (i), 2-lfethylbutanal- (i), 2-methylpentanal- (i), 2-methylhexanal- (i) and the corresponding, in the side chain, ethyl, propyl, butyl, etc. radicals containing aldehydes, such as 2-Äthylpropanal- (i), 2-Äthylbutanal- (i) etc. Such aldehydes or mixtures are easily accessible technically, e.g. B. by dehydration of the higher alcohols obtained from the hydrogenation of carbon monoxide, such as isobutyl, Isoamyl, isohexyl and isoheptyl alcohol.

Glycol half esters or the glycols obtainable therefrom by saponification and acids are valuable products that can be used either as solvents, plasticizers and Pesticides or as intermediate products in the manufacture of textile auxiliaries Can be used. Example ioo parts by weight of 2-methylpentanal- (i), the by catalytic dehydrogenation of the fraction from boiling point 145 to i49 ° of a carbon dioxide hydrogenation product was obtained through a cooler and a container in which .I parts by weight Lumpy: store 3tznatroii on sieves, pumped around with temporary cooling, whereby the temperature of the reaction mixture does not exceed 40 °. After 3 hours it is Condensation ended. It is then acidified with hydrochloric acid and washed out. at the subsequent distillation goes up to 160 ° at 10 mm a total of 29 parts by weight Forward over. Of these, 4 parts by weight are isohelylic acid and 3 parts by weight are isohexyl acid isohexyl ester. The remainder is unchanged aldehyde, which condensation again after the distillation is subjected and again yields io parts by weight of half esters. The main faction can after distilling off the first run immediately with hydrogen in the presence of catalysts be treated. 67 parts by weight of the colorless isohexyl acid ester are obtained in this way des 2,4-Dimethyl- (2) -n-propylheptanediols- (i, 3), which is between 16o and 18o ° at io mm passes. The residue is 1.5 parts by weight.

By saponification, 2 parts by weight of the half-ester can be converted into 2, I-dimethyl- (2) -n-propylheptanediol -(1, 3) (boiling point 152 'at 10 mm) and 27 parts by weight of isohexyl acid (boiling point 1g4 °) obtain.

EXAMPLES 3 parts of sodium amide are added to 100 parts by weight of 2-methylpentanal- (i) in a kettle with stirring and cooling. The temperature rises rapidly to around 50 °. The reaction mixture is brought to room temperature by strong cooling and kept there. After 2 hours, after the sodium amide has settled, it is decanted from it. The reaction product is worked up as in Example i. There are 67 parts of the isohexyl acid ester of 2,4-dimethyl- (2) -n-propylheptanediol- (i, 3) with a boiling point of 16o to 180 ° io mm, 15 parts of unchanged aldehyde, 5 parts of isohexyl acid with a boiling point of 194 °, 6 Parts of intermediate runs (ester) and 3 parts of residue are obtained. Example 3 ioo parts Isoheptylaldehyd (b.p. 1 30 ° to 135 °) is stirred with 3 parts of solid sodium hydroxide under cooling for 2 hours. The subsequent steam distillation after neutralization with hydrochloric acid yields 25 parts of steam distillate. Subsequent vacuum distillation gives 60 parts of the isoheptylic acid ester of 2,4,6-trimethyl-2-isobutylheptanediols (r, 3) with a boiling point of 170 to igo ° at 10 mm. The lead is 3 parts, the residue is only i part. Example 4 100 parts of chemically pure z-methylpentanal- (i) are condensed according to Example 3. Work-up gives 3 parts of steam distillate, 3 parts of isohexyl acid, 1 part intermediate run, 88 parts of the isohexyl acid ester of 2,4-dimethyl- (2) -n-propylheptanediol- (1, 3) and 1 part of residue. EXAMPLE 5 100 parts of aldehyde mixture obtained by catalytic dehydrogenation of the fraction from boiling point 145 to 162 ° of a carbon dioxide hydrogenation product (the mixture preferably consists of isohexyl and isoheptyl aldehyde) are condensed with 3 parts of solid caustic soda. After separating off the first runnings, parts 1, 3-glycol half-ester mixture with a boiling point of 165 to igo ° at 10 mm can be obtained.

Claims (1)

PATENT CLAIM: Process for the preparation of 1,3-glycol half-esters by condensation of aliphatic aldehydes, which are substituted by alkyl groups in the a-position to the carbonyl group, with alkaline condensing agents, characterized in that the condensation is carried out in the presence of solid caustic alkali or sodium amide or mixtures carries out these substances at temperatures below 100 ° in the absence of solvents.