DE475918C - Method for the preparation of vanillin - Google Patents

Description

Process for the preparation of vanillin By G uyot and G ry (Comptes rendus de 1'Academie des Sciences, Vol. 149, pp. 928 to 931) it has become known - that the condensation products of diketocarboxylic acid esters or mesoxalic acid esters with guaiacol by heating in boiling 4-dimethylamino-t-methylbenzene can be converted into vanillin. The poor accessibility of the acid esters used meant that these vanillin syntheses were of no technical importance.

It has now been found that the very easily accessible condensation product of chloral hydrate with guaiacol (reports from the German Chemical Society, Vol. 56, p. 982) in a very simple way and in one operation by saponification and oxidation gives vanillin by turning it into one at the same time or one after the other and the same aqueous solution of saponification and oxidation by reducible Subjects heavy metal compounds. In contrast to the way G u y o t works and G r y here is not the use of a carbonic acid-splitting agent necessary.

Now it is known that in the oxidation of mandelic acid in addition to other oxidation products also form benzaldehyde. But it was clear from the information the literature (Liebigs Annalen, vol. 18, p. 321) do not conclude that from oxymethoxymandelic acid, which arises from the trichloromethylguaiacylcarbinol by saponification; the corresponding Aldehyde in good yield would be obtained because, the mandelic acid and the Oxym (ethoxymandelic acid show extensive differences in their reactions; so are z. B. the oxidation of mandelic acid a. a. O. used oxidizing agent - Chlorine and nitric acid - not suitable for treating oxymandelic acids because Chlorination or nitration would occur.

While also the trichloromethylphenylc-arbinol when boiling with potassium carbonate decomposes in benzaldehyde and chloroform, is evident from the same treatment of trichloromethyl bauajacylcarbinols not even trace a formation of vanillin and chloroform. But there is also oxymethoxymandelic acid, oxidized with copper acetate or carbonate, in good yield vanillin, while mandelic acid does not contain benzaldehyde at all supplies. If the oxidation is carried out with manganese dioxide and lead peroxide, then it proceeds experiments have shown, however, in the same sense; it arises from Mandelic acid Benzaldehyde next to benzoic acid and from Oxym @ ethoxymandelic acid vanillin next to vanminic acid.

According to the reports of the German Chemical Society (Vol. 56, P. 983, para. 3, and p. 98o, para. 5) became triichloromethylguaiaacylcarbinol Vanillin on different. Because of preserved, but only in just detectable quantities according to processes that cannot be used for technical egg production.

If the oxidation of mandelic acid to benzaldehyde cannot be evaluated from a technical point of view, since it leads from a valuable intermediate product to a cheap end product, the depiction of vanillin represents a valuable new addition to technology, as it enables high-quality vanillin to be obtained from the recently easily accessible oxymethoxymandelic acid made possible in good yields and in technically feasible operations. Example 1 50 g of trichloromethylgüajacylcarbinol are in q. 1 water boiled under reflux for 12 hours. After the addition of 759 copper acetate, the solution is boiled for a further 12 hours, then it is evaporated to 2 liters. The solution is etherified. The essential solution contains 8 g vanillin. _. Example 2 50 g of trichloromethylguaiaacylcarbinol are mixed with q. 1 water heated to boiling on the reflux condenser for 12 hours. After adding 20 g of copper acetate, the mixture is boiled for about 12 hours while blowing in air. The vanillin is removed from the cooled solution by ether or chloroform. Example 3 50 g of trichloromethylguaiaacylcarbinol and 20 g of copper acetate are in q. 1 water heated to boiling for 12 hours on the reflux condenser while blowing in air. The vanillin is extracted from the cooled solution. Example q.

20 g of trichloromethylguaiaacylcarbinol, 309 copper acetate and 1 liter of water are heated to 150 ° for 2 hours in a closed vessel. The vanillin formed is extracted. Example 10.8 g of trichloromethylguaiaacylcarbinol are dissolved in 1,600 g of water, then 16.2 g of copper acetate are added. The discoloration with the formation of cupro salts takes place very quickly. The boiling is then continued for several hours until a sample taken out does not reveal any further formation of hydrochloric acid due to saponification. The vanillin is shaken out of the solution. Yield: 5.5g vanillin.

Example 6 10.8 g of trichloromethylguaiaacylcarbinol are in 160 g Dissolved water and, after saponification by boiling, with 17.28 g of mercury oxide offset. Yield: 2 g vanillin.

In the previous example one can denote the mercury oxide by "the equivalent Replace amount of lead peroxide; you also get vanillin in this way.

Claims (1)

PATENT CLAIMS. Method for the preparation of vanillin, characterized in that that Trichloromethylguajacylcarbinol simultaneously or successively in one and the same aqueous solution of saponification and oxidation by reducible heavy metal compounds subject.