ewok_poacher - 20-11-2007 at 11:23
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.
could someome translate this? Benzaldehyde does what in 50% water/sulfuric acid when heated?
Klute - 20-11-2007 at 11:59
I think the only thing out can get from boiling benzaldehyde in sulfuric acid is TAR.
And isn't the text written in english? If you can't understand a word, you won't get any P2P out of that.
[Edited on 20-11-2007 by Klute]
Nicodem - 20-11-2007 at 13:34
Translation into which language? And why would stupid people need such a translation?
PS: There already is a thread for requesting translations. There was no need to open another one.
Xenoid - 20-11-2007 at 14:17
Duh!!
I think what ewok-poacher requires is a translation from poorly written scientific gibberish into easily readable english!
For example, is there somewhere hidden in this gem of convoluted obfuscation, an explanation of the reaction benzaldehyde would undergo when heated
with 50% sulphuric acid!
He is implying he is too stupid to find it, if it's there! Don't ask me, I gave up organic chemistry 40 years ago!
Regards, Xenoid
S.C. Wack - 20-11-2007 at 14:46
Hopefully, Nicodem is not actually requesting that this be posted in a requested translations thread.
ewok_poacher, it seems obvious that whatever reference this is does not mention benzaldehyde in any way, not surprising since they are not looking at
benzaldehydes.
What reference is that, BTW?
[Edited on 20-11-2007 by S.C. Wack]
trilobite - 20-11-2007 at 18:53
I bet this is an english translation of <i>Berichte</i> <b>60</b>, 1050 (1927) by Danilov and Danilova where they isomerize
hydratropic aldehyde to P2P with conc. sulfuric acid, originally published in German. IIRC it has nothing to do with benzaldehydes.
garage chemist - 20-11-2007 at 19:12
Then post the actual german text, not some automated translation.
Although this translation, if it really is an automated one, is much more comprehensible than usual. If english is your mother tongue you will have no
problems with it.
I can translate german texts into english if you ask me nicely. Since I dont read every thread here, U2U me if I dont respond to a thread where a
translation of a german text is sought after.
[Edited on 21-11-2007 by garage chemist]
solo - 20-11-2007 at 19:47
This is the elusive translation he's looking for.....I think, acquired for me years ago......solo
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)
[Edited on 20-11-2007 by solo]
Attachment: Hydro.pdf (79kB)
This file has been downloaded 1980 times
solo - 20-11-2007 at 20:56
Uaber die Beziehungen zwischen dem asymm. Methyl-phenyl-athylenglykol
und den ihm entsprechenden Anhydro-Formen.
S. Danilow und E. Venus-Danilowa
Berichte 60, 1050 (1927)
Attachment: Uaber die Beziehungen zwischen dem asymm. Methyl-phenyl-athylenglykol. und den ihm entsprechenden Anhydro-Formen..pdf (1.4MB)
This file has been downloaded 1036 times
ewok_poacher - 20-11-2007 at 21:19
xenoid was right in defining my request. My request was two part
1 translate to easily understandable
2 can this method be applied to benzaldehyde
trilobite - 20-11-2007 at 22:00
Translate to cluelesslish creole? Or maybe colloquial idiotish pidgin? If you want to understand you should learn chemistry, not ask to be spoonfed.
Please do go somewhere else, you really do not deserve the answer.
And thank you Solo for interesting reading. I never tried to find out more about the research of Danilov and his wife than the Berichte article.
ewok_poacher - 20-11-2007 at 22:04
Well thank you for the insightful reply.
I am trying to learn but cannot afford anything more than a couple books and internet access. I had hoped asking questions would be a good way to
learn.
Polverone - 21-11-2007 at 10:01
Visit the forum library at www.sciencemadness.org/library/. Then sign up for an account on gigapedia.org and go to their chemistry section. You will have a lot more material
to learn from and a lot fewer reasons to ask for spoonfeeding. If you have a computer and internet connection, you have access to a world of
instructional material at zero cost.