DE1084711B - Process for the preparation of high molecular weight ª,ª-unsaturated aldehydes - Google Patents

Description

Process for the preparation of a, p-unsaturated aldehydes with high Molecular Weight The invention relates to the preparation of α, γ-unsaturated aldehydes by catalytic condensation of monomeric aldehydes.

In the known processes for the preparation of aldehydes with high There are several serious difficulties in molecular weight. These difficulties come from the great reactivity of the aldehyde itself. Aldehydes become very polymerizes easily and quickly. They occur in many addition and condensation reactions a. They are themselves reducing agents and are very easily oxidized. Because of these Their ability to react is hindered by many side reactions. There are usually only low yields, and also the separation of the aldehyde from the reaction mixture is generally difficult.

According to the invention for the known production of unsaturated Aldehydes by aldol condensation in the presence of catalysts certain condensation catalysts, namely metallic soaps of fatty acids, used to condensation of 2 molecule To catalyze the aldehyde to the aldol, while the further to the unsaturated aldehyde leading steps are known and for this purpose within the scope of the present invention no protection is claimed. This affects the dehydration from the aldol to one to obtain unsaturated aldehyde with large molecular weight.

It has been found that the essential part of the catalyst used according to the invention for the aldol condensation is an ion of one of the following metals: chromium, manganese, iron, cobalt, nickel, copper, i.e. H. of elements of atomic number 24 to 29. A metal ion concentration of 10 to 200 parts per million has also been found to be advantageous, although slightly higher or lower concentrations have been found to be effective. Preferably the metal ion is added to the reactants in a form which is soluble in the aldehyde, e.g. B. as a fatty acid soap. Iron and copper stearate or caprylate have been found to be very effective and are particularly recommended as useful catalysts.

In the course of the condensation, an aldol is formed by the addition of one molecule of aldehyde to the carbonyl group of the other molecule. This addition depends on the activated type of hydrogen in the a-position, i. H. of the hydrogen attached to the carbon atom adjacent to the carbonyl group, namely the attached molecule. A hydrogen arranged in this way in the molecule is generally referred to as activated α-hydrogen. The aldol condensation therefore only occurs in aldehydes which have at least one hydrogen atom in the a-position in the attaching molecule. An aldol is formed in which a hydroxyl group is present in the molecule in the β-position adjacent to an activated α-hydrogen. Under these favorable circumstances, water is easily removed by the application of heat in a known manner.

In a preferred process, the aldehyde is with the catalyst refluxed to form the aldol and the water removed from the aldol is distilled off from the reaction mixture. The reaction is therefore under im performed under essential anhydrous conditions.

Example I 72 g (0.5 mol) of decanal and 0.2 g of iron stearate are placed in a 200 ml round bottom flask. The mixture is heated to 110 to 1150 ° C. under 15 mm pressure for 2 hours. The water of reaction is removed by distillation in the course of the reaction. The reaction mixture is then distilled at 1 mm pressure; after approximately 28% decanal have been removed, the main fraction is collected at 170 to 172 ° C. and 1 mm of mercury pressure in an amount of 701 / o of the theoretical yield of 2-octyl-2-dodecenal.

Example II To a round bottom flask is placed 1 mole (128 g) of octanal containing 200 parts per million cobalt catalyst. The cobalt is introduced in the form of the fatty acid soap cobalt stearate, the mixture is then refluxed for 8 hours at approximately 130 ° C. at 15 mm pressure. The water of reaction is removed by distillation as the reaction progresses. The reaction mixture is worked up by distilling under reduced pressure. First, 22 starting material octanal are removed, then 85 - of the end product 2-hexyl-2-decenal are obtained. The yield is 75 "/ o of the egg theory. Example, 111 1 mole (128 9) Oetanal containing 200 parts per million manganese catalyst is brought into a round bottom flask. The manganese is introduced as the fatty acid soap Mangancaprylat. The mixture is 8 hours at 15 mm pressure to about 130 ° C. The water of reaction is removed in the course of the reaction. The reaction mixture is worked up by distillation under reduced pressure. First 30 g of the starting material octanal are removed, then 72 g of the end product 2-hexyl-2 The yield is 70% of theory. Example IV 60 g of octadecanal, containing approximately 200 parts per million cobalt catalyst, are placed in a round bottom flask. The cobalt is introduced as the fatty acid soap cobalt stearate. The mixture is then stirred for 16 hours at 9 The reaction mixture is heated under reflux at a pressure of about 135 ° C. The water of reaction is removed by distillation in the course of the reaction is then worked up by distillation under reduced pressure. Analysis of the crude product showed that it contains 81 % of the theoretical yield of 2-hexadecyl-2-eicosenal.

The following comparative experiment shows the progressiveness of the inventive method: - Ineinen200 cc Rundkolbenwurden100gDecanal and brought 5gNatriumhydroxyd. The mixture was heated at 70 to 75 'for 4 hours at a pressure of 10 mm. A small amount of water was removed by distillation. The reaction mixture was filtered and distilled at a pressure of 1 mm. 95 g of the starting material decanal were recovered at 60 to 65 ° C. No 2-octyl-2-dodecenal was obtained. The failure of the aldol condensation could be due to the insolubility of the catalyst in the reaction mixture. Similar results are obtained using the other common catalysts, namely sodium ethoxide, calcium carbonate, sodium carbonate and potassium hydroxide.

Claims (1)

CLAIMS: 1. A process for preparing a, fl-unsaturated aldehydes having a high molecular weight t 'ge of the resulting water from the Al # dol by aldol condensation in the presence of catalysts and continuous withdrawal, characterized indicates overall that the catalyst used for the condensation a metal soap "in which the cation is chromium, manganese, iron, cobalt, nickel or copper and in which the anion is a fatty acid anion with 6 to 22 carbon atoms is used, 2nd embodiment of the method according to claim 1, characterized by 3. Process according to Claim 2, characterized in that the condensation is carried out during 2 hours of heating to 110 to 115 ° C at 15 mm pressure to claim 1, characterized in that an aldehyde is used having at least 8 carbon atoms has. 5.- Verfahr'en according to claim 1, characterized labeled in draws that a metal salt of caprylic acid or stearic acid is used as a catalyst. . 6. The method according to claim 1, characterized in that copper stearate or iron stearate is used as the catalyst. Considered publications: Houben-Weyl: Methods of Organic Chemistry, 4th Edition, Vol. VII, Part 1, pp. 76 to 79.