DE927627C - Process for the production of higher molecular weight polyenals - Google Patents

Description

Process for the preparation of higher molecular weight polyenals It is known that crotonaldehyde and its vinylene homologues can be condensed in the presence of secondary organic bases or their salts with organic acids to give straight chain polyenals. However, according to the literature, these condensation products are obtained in comparatively very low yields and, for unknown reasons, also fluctuating yields. The main products of the reaction are cyclic bodies. The elucidation of the mechanism of this condensation has shown that the intermediate product of this reaction is an I-dialkylamino-butadiene of the formula is that, as a diene, easily attaches to dienophilic components to form derivatives of dihydrobenzene. Under the condensation conditions used so far, ie by working with undiluted crotonaldehyde in the presence of small amounts of a catalyst, this reaction is very much favored, since there is a high probability that the reactive intermediate product of the dienophilic components present in large excess, e.g. B. crotonaldehyde, is captured.

It has now been found that higher molecular weight can be obtained in good yield Polyenals, especially those with at least 12 carbon atoms, are obtained if the starting point for the condensation is acetaldehyde and the reaction temperature is advantageous in the vicinity of the boiling point of acetaldehyde, so that each is formed Intermediates in the lap of acetaldehyde a lesser possibility to enter into diene syntheses and thus prefer linear condensation will. The polyenals can be converted into carboxylic acids in a known manner or higher molecular weight, in hydrogen-rich aldehydes and in the corresponding convert primary alcohols, supplied to the known technical uses can be. The mixtures obtained, as such or after decomposition into individual fractions provide an equivalent substitute for fatty acids, fatty aldehydes and Fatty alcohols.

Example I56 parts by weight of acetaldehyde (98 to 100%) with 4 parts by weight of piperidine and the amount of acetic acid necessary for neutralization added and kept at 15 to 200 by cooling. After the heat tint subsided one adds the same amount of the catalyst again and repeats this measure again, allowing the temperature to rise to 250. -You get after 16 hours Standing at 15 to 200 a dark red thick slurry of a mixture crystallized Polyenal, which is purified by washing with methanol. The polyenals obtained are very sparingly soluble in common solvents, they can be in known way by hydrogenation into saturated aldehydes or saturated alcohols convict.

Instead of the piperidine acetate one can also use the crotonic acid salt or the formate or butyrate of piperazine or other effective salts of secondary Use bases.

Claims (1)

PATENT CLAIM: Process for the production of higher molecular weight polyenals, characterized in that acetaldehyde, optionally in the presence of solvents, in the liquid phase with or without pressure in the presence of organic secondary bases, especially their salts, condensed with themselves at temperatures below 100 °.