DE351137C - Process for the preparation of ª ‡ -Chlorcrotonaldehyde - Google Patents

Description

Process for the preparation of α-chlorocrotonaldehyde. r / -Chlorcrotonaldehv (1 was developed by L i e 1) e n and Z e i s e 1 by condensation of chloroacetaldehyde with Acetaldehyde obtained and from Pen ner in a small amount in the chlorination product detected by paraldehyde. Chloracetaldehvd has so far only been very cumbersome Wise zit win, so that of a reasonably technically feasible production of a-chlorocrotonaldehyde cannot be discussed after the procedures mentioned.

It has now been found that from crotonaldehyde by the addition of i 1'1o1. A-ß-dichlorobutyraldehyde, which is quantitatively produced in the cold, for chlorine Z e i s e 1 as an intermediate in the preparation of a-ß-dichlorobutyryl chloride from crotonaldehyde, with aqueous alkalis (acetates, carbonates, caustic alkalis), but even with water, an equivalent of hydrochloric acid is split off with self-heating and thereby converts into α-chlorocrotonaldehyde. . Such elimination of hydrogen chloride from α-ßchlorinated aliphatic .Verbindungen are generally known. It was however, it cannot be foreseen that such a reaction in this case will be so smooth and would take place completely, especially since the cc-ß-dichlorobutyraldehyde is an extremely unstable one Is substance that z. B. in the distillation (also in a vacuum) with resinification to major parts is decomposed. From the for a-bromocrotonaldehyde (reports of the Germans Chemischen Gesellschaft, Volume 44, page 1164) described elimination of hydrogen bromide by anhydrous acetate differs significantly (read new 1-experienced by here the cleavage is caused by the action of the solvent (water) and the added alkali merely removes the hydrochloric acid from the reaction mixture aims.

The α-chloro-red aldehyde obtained in this way is almost colorless and shows up distillation with steam the correct boiling point of 147 to 1 ¢ 9 °.

The value of this cheap process is that it is now practical Production of butyrchloral hydrate by further addition of chlorine.

Example. In 70 parts of crotonaldehyde, 71 Part of chlorine initiated. When the absorption is complete, the mixture is left with cooling and Stir in 100 parts of water. After a while, the necessary amount will be available Quick lime neutralized, the a-chlorocrotonaldehyde formed is blown off with steam, dried and rectified. Yield 80 to 90 percent of theory. Instead of water and quick lime can just as well solutions of acetates, soda, caustic soda directly be used.

Claims (1)

PATENT CLAIM: Process for the preparation of α-chloro-rotonaldehyde, characterized in that the α-β-dichlorobutyraldehyde obtainable from crotonaldehyde and chlorine is treated with water or aqueous alkalis.