Hydrotropic aldehyde(2-phenylpropanal) to P2P Reference....

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azole
(One Remarkable HyperLab Bee)
12-12-03 12:51
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The ill-fated article...

Hydro- and solvatolytic and intramolecular oxidation-reduction.
II. Acid and acid-salt catalysis in the isomerisation of aldehydes to ketones.
S. N. Danilov
Zhurnal Obshchei Khimii, 18(11), 2000-2007 (1948). (http://chemister.fannet.ru/Books/Chembooks/Zhurnals/ZhGenChem1948-11.djvu)
(retrieved by murmur and hosted by Chemister of HyperLab)

   The article is damn lengthy (8 pages) and consists mostly of general discussion on catalysis and of speculations as to possible mechanisms of catalytic isomerisations of aldehydes to ketones. The language of the article is most cumbersome; quite common are repetitions and phrases spanning 6-8 lines of text. Unfortunately, the author was at the same time the editor-in-chief of the journal, so he couldn't be forced to present a concise report with clearly written experimental part. Overall, only half of the article is relevant, and has been translated.

<...> The same catalysts which proved to be valuable for acetylene hydration were found to catalyse isomerisation of aldehydes to ketones (S. N. Danilov, E. D. Venus-Danilova, [4]). <...> Danilov and Venus-Danilova didn't examine isomeric transformations of monosubstituted acetic aldehydes like propionic or phenylacetic but there is no doubt that such aldehydes, in spite of ease of their condensation, can isomerise to ketones similarly to tri- and disubstituted acetaldehydes...<...>
   ...The transformation of aldehydes to ketones occurs easily under some heating in the presence of mercuric salts and especially easily, one may say, immediately, under the action of concentrated sulfuric acid with cooling. In this process, mercuric salts and concentrated sulfuric acid form loose complexes with the reactants and the reaction products. The end-products of the reaction (ketones) form more stable complexes than aldehydes do. This accounts for the fact that only ketone can be found in these complexes, especially in the case of concentrated sulfuric acid. <...>
   Recently, T. E. Zalesskaya [8], while studying isomerisation of aldehydes to ketones at high temperatures in the presence of zinc chloride according to Favorskii [9], indicated the presence of the compounds of ketones with zinc chloride. If the mixture wasn't treated with water, it was impossible to distil the ketones from the reaction flask. Apparently, this can be explained by decomposition of stable complexes of zinc chloride with ketones rather than by elimination of the destructive action of zinc chloride.
   That zinc chloride causes isomerisation of ethylenic oxides is known for a long time [10]. Danilov and Venus-Danilova [11] found that ethylenic oxides can be converted either into aldehydes or into ketones, depending on the concentration and the power of the acidic agent applied. Isomerisations of ethylenic oxides and aldehydes to ketones proceed under identical conditions.
   Isomeric transformation of aldehydes into ketones was first observed under the conditions of dehydration of alpha-glycols caused by dehydrating agents and in the course of acidic hydrolysis of oximes and semicarbazones of aldehydes.
Danilov and Venus-Danilova performed the transformation of aldehydes to ketones under the conditions of homogeneous catalysis in the presence of mercuric salts and acids. Danilov [12] carried out the experiments concerning isomerisation of aldehydes under the conditions of heterogeneous catalysis (over aluminum sulfate). Later, this isomeric transformation was performed by Ramart-Lucas [13] at high temperatures under the conditions of heterogeneous catalysis, the role of high temperature and the surface area being obvious in this case.<...>
   Isomeric transformations of aldehydes to ketones are natural in the sense that the heats of combustion of aldehydes are higher than those of ketones. Depending on the reaction conditions and the structure of an aldehyde, these transformations can proceed quantitatively, or they can be accompanied by other reactions <...>, e.g. aldol condensation... The isomerisation of aldehydes to ketones proceeds at enormous reaction rates when carried out at low temperatures in concentrated sulfuric acid which dissolves both the reactants and the products. Reversibility of the isomerisation ... was not observed so far...
   Isomerisation of aldehydes to ketones is usually performed with large amounts of a reagent-catalyst because the latter serves as a solvent or, like <solutions of> mercury salts, is taken in excess to facilitate stirring.<...>
   Of course, the transformation can be accomplished using a small amount of an acidic agent. This was done a long time ago (in 1919) for triphenylacetic aldehyde which was isomerised to ketone in the presence of a small amount of HCl or HBr, acetic acid being the solvent. That is why one can state that a large amount of sulfuric acid is applied <only> to ensure the reaction mixture being homogenous and to facilitate stirring, so the reaction... is nevertheless catalytic.
   The agents causing ketonic transformation of aldehydes are not consumed in the course of the reaction, so it meets ... the criterion of being catalytic. However, concentrated sulfuric acid binds to the emerging ketone to form a molecular compound which is decomposed easily by water in the course of isolation of the reaction products.
   The ability of carbonyl compounds to form hydrates or other molecular compounds and to bind to acids and salts is known for a long time [5]. Molecular compounds of ketones with concentrated sulfuric acid [18] were reported recently. It is also known that aldehydes and ketones form compounds with HgCl2...
   One may suppose that concentrated sulfuric acid catalyses isomerisation of aldehydes to ketones because its compounds with ketones are more stable than those with aldehydes (this needs to be supported experimentally), so the reaction is directed to the formation of the complex formed from a ketone and sulfuric acid. Danilov showed that in the case of cyclohexylhydrobenzoin [19], action of sulfuric acid on the glycol leads to only one ketone of two possible. The same ketone is formed in course of isomerisation of the corresponding aldehyde.<...>

Experimental part.

<...> The best yields were obtained in the isomerisation of trisubstituted acetaldehydes, then follow disubstituted acetaldehydes and aldehydes of polymethylene series. The presence of aromatic moieties in the molecule facilitates the ketonic transformation of aldehydes. These conclusions are still purely qualitative... <...>

1. Isomerisation of aldehydes in the presence of acids.

   Experiments showed that in the case of dilute aqueous acids no quantitative transformation of aldehydes to ketones was observed, starting either from an aldehyde itself or from its oxime or semicarbazone. Thus, triphenylacetaldehyde is in part isomerised to triphenylethanone on heating with 45% sulfuric acid.
   Methylphenylacetic aldehyde isomerises to benzyl methyl ketone: C6H5(CH3)CHCHO --> C6H5CH2COCH3 on heating with 50% sulfuric acid in an oil bath (temp. 145?) to give 46% of the theoretical yield of the ketone, the product being in part converted into condensation products. Better yield of the ketone (65%) is achieved if methylphenylacetic aldehyde semicarbazone is heated in 15% sulfuric acid at 120? bath temperature.
   Diphenylacetic aldehyde gave a mixture of the ketone (deoxybenzoin) and the aldehyde (60-65% ketone content) on heating with 50-75% sulfuric acid to the boiling point of the acid solution. However, the oxime of the aldehyde converted almost quantitatively to the ketone under these conditions, that is, more easily than the aldehyde itself.
   Still better yield of a ketone (para-deoxytoluoin) resulted from the reaction of di(para-tolyl)acetic aldehyde with dilute aqueous sulfuric acid (50-60% concentration). In an alcoholic solution of sulfuric acid the aldehyde did isomerise to the ketone but a hydrocarbon, namely symm-ditolylethylene, was also formed. Alcoholic medium facilitates the reactions of decomposition of carbonyl compounds.   No characteristic coloration was observed in dilute acids. Similar results were obtained with a number of other aldehydes heated with dilute acids to boiling. In almost all cases neither the starting aldehydes, nor the ketones formed did dissolve in the aqueous acid, thus requiring vigorous stirring to attain better contact of the aldehyde with the acid. More rapid was the reaction in concentrated sulfuric acid under the conditions of homogeneous catalysis, peculiar color changes being observed.
   In the case of concentrated sulfuric acid the yields were sometimes reduced because of formation of condensation products; the reaction products didn't contain the starting aldehyde. The experiment is carried out as follows: to sulfuric acid (sp. grav. 1.84) cooled to -20? or to -10? an aldehyde is added with stirring; dissolution occurs quickly. The solution acquires yellow, red, brown to deep black coloration. Thus, in the case of methylphenylacetic aldehyde the color was brown, with diphenylacetic aldehyde it was black, with cyclohexylphenylacetic aldehyde the mixture was dark cherry-coloured and so on. On pouring the mixture onto ice, the color disappeared, and the ketone was isolated in quantitative yield, or, if the aldehyde condensed easily, in lower yield. Ethyl phenyl ketone formed brown-red solutions in sulfuric acid (sp. grav. 1.84) at -10?; unchanged ketone was separated on pouring the mixture onto ice, since this ketone doesn't undergo isomerisation to another ketone under the conditions indicated.
   Interestingly, an aldehyde is converted to a ketone immediately after dissolution in <conc. sulfuric> acid; in certain cases condensation products are formed. Alpha-glycols, especially those containing aromatic moieties in their molecules, form bright-coloured (red) solutions in concentrated sulfuric acid. After dilution of the acid, the color disappears and carbonyl compounds can be isolated with no admixture of the starting glycol being present.

2. Isomerisation of aldehydes in the presence of mercuric salts.

   Solutions of mercuric chloride, bromide, or sulfate (with some sulfuric acid added) in aqueous ethanol heated to boiling can be applied to isomerise aldehydes to ketones. A loose precipitate is formed soon. When treated with steam, it forms a mixture of an aldehyde and a ketone, or sometimes even pure ketone. For example, methylphenylacetic aldehyde formed a loose precipitate on heating in a water-ethanol (75% ethanol) solution of mercuric chloride (7% HgCl2). On treatment of the reaction mixture with steam, almost pure benzyl methyl ketone was obtained.
   E. D. Venus-Danilova and A. I. Bol'shukhin [20] applied a solution of mercuric sulfate in aqueous ethanol with addition of sulfuric acid to isomerise cyclohexylphenylacetic aldehyde. Heating was conducted for 6 h at 130?; white flakes formed in the solution; benzyl cyclohexyl ketone was obtained in 60% yield.

References.

4. S. N. Danilov and E.D. Venus-Danilova, Zhurnal Russkogo Khimicheskogo Obshchestva, 51, 97 (1919); 61, 53 (1929). Venus-Danilova, Zh. Obshch. Khim., 8, 1179, 1438 (1938).

5. B. N. Menshutkin, Zhurnal Russkogo Khimicheskogo Obshchestva, 41, 1089 (1909); 42, 1298 (1910); 54(2), 22 (1923).

8. T. E. Zalesskaya, Zh. Obshch. Khim., 8, 1589 (1938); 16, 1813 (1946).

9. A. E. Favorskii, Zh. Obshch. Khim., 5, 1728 (1935).

10. K. A. Krasuskii, "A study on isomeric transformations of organic oxides", Peterburg, 1902, p. 86.

11. S. N. Danilov and E. D. Venus-Danilova, Zhurnal Russkogo Khimicheskogo Obshchestva, 59, 187 (1927); Venus-Danilova, ibid., 61, 1479 (1929).

12. S. N. Danilov, Zhurnal Russkogo Khimicheskogo Obshchestva, 61, 723 (1929).

13. Ramart-Lucas, Bull. Soc. Chim. France, 45, 480 (1929); 49, 1863 (1931).

18. Hammet, J. Amer. Chem. Soc., 59, 1708 (1937).

19. S. N. Danilov, Zhurnal Russkogo Khimicheskogo Obshchestva, 58, 129 (1926).

20. E. D. Venus-Danilova and A. I. Bol'shukhin, Zh. Obshch. Khim., 9, 975 (1939).

java
(Hive Bee)
12-12-03 14:18
No 476455




RE:2-phenylpropanal to P2P Reference.....
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azole...Muchas Gracias (many thanks) my fellow Bee, your efforts are not forgoten......Happy Holidays from Latin America......java

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