Boffis
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Vicinal dione monoxime in aqueous medium?
In this thread by magpie;
http://www.sciencemadness.org/talk/viewthread.php?tid=8122#p...
he describes the preparation of dimethylglyoxime via dimethylglyoxal monoxime. The procedure is described in, amongst other places, Vogel's Textbook
of practical organic chemistry, 3rd edition. The initial step is the reaction of an alkyl nitrite with butanone under the influence of hydrogen
chloride. In the thread referenced above kmno4 provides a reference (with links) that suggest that it is possible to carry out this reaction with
aqueous HNO2 prepared in situ and asked if anyone had ever tried this:
Quote: Originally posted by kmno4  | Mmmmmm....
According to:
A Practical and User-Friendly Method for the Selenium-Free One-Step Preparation of 1,2-Diketones and their Monoxime Analogs (Synlett,
2004)
there is no need to use any alkyl nitrite to prepare oximes.
They use THF(or dioxane)/NaNO2/HClaq to prepare these compounds.
More, there is suggestion that oximes (isonitrosoketones) of 1,2-diketones can be obtained in H2O/NaNO2/HClaq
in the case of soluble ketones.
My question is: Has anybody ever tried to prepare monooxime of biacetyl from MEK in this or similar way ??
[Edited on 24-7-2007 by kmno4] |
Since no one at the time took him up I think we can safely assume that the answer was no!
So once again I find myself sitting there thinking ... mmm nice idea lets try it!
So this afternoon I prepared a solution of 0.1 moles of NaNO2 in 30ml of water and added 9ml (0.1moles) of butanone, chilled the mixture in the
freezer to about -12 C and then added it to 8.6ml (0.1moles) of 36% HCl diluted with an equal volume of water and also chilled to about the same
temperature. The low temperature was used to try and maximise the stability of the liberated nitrous acid in case the reaction was slow.
Butanone is only moderately soluble in water and in theory inorganic salts should reduce this miscibility still further. This, in fact, appears to be
the case, even with vigorous stirring the reaction mixture was biphasic. The organic phase turned an amazing shade of blue while the aqueous phase
turned a greenish colour. It appears therefore that butanone simply extracts the nitrous acid from the aqueous phase but I could see no evidence of
any reaction. I added an extra 3ml on 36% HCl in the hope that this would help the reaction along but no solid mono-oxime has yet formed. I will leave
it over night and then see what I can find in it tomorrow.
In the various links in the thread mentioned above I found a paper by Fiteli in Gazz. It. Chim. which may hold a clue to the reports of aqueous phase
nitrosation of methylenic ketones. It is in Italian and very obscure. To my amazement the gods of the search engine came up trumps but its going to
take me a few days to wade through it.
My initial conclusion may be a little hasty but it appears that nitrous acid simply partitions into butanone forming a nice blue solution but doesn't
actually react with it. The nitrous acid slowly decomposes and the solution loses its colours.
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karlos³
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Huh?
Yeah I tried that exact reaction, in THF with propiophenone, and added under cooling, some technical 31-33% HCl to the stirred suspension of KNO2.
That worked actually great.
I have tried it in dioxane by the way too, but it was frustrating, of course the whole reaction mixture solidified under cooling... I had to add THF
to get it going again.
I am sure it has worked great for the MEK too, you probably just have to adjust the workup to get it out.
Sorry, I just wanted to say yes I did that reaction and did so successfully, but I am actually with one leg in my bed already, I will put some more
effort into a better reply tomorrow 
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Boffis
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Hi Karlos, but you used THF as a solvent I am talking about carrying out this reaction in water with no co-solvent and only enough MEK to react with
the nitrous acid formed in-situ. I evaporated down the reaction mixture after neutralizing the excess HCl this morning to remove the excess MEK and
water. I did this in a large shallow basin so the temperature never exceeded 70 C and extracted the salt residue with methanol and then evaporated the
methanol. All I was left with was a little heavy yellow oil with a peculiar but not unpleasant smell, no crystalline solid. So failure.
I'll have a look at Fileti's work when time permits.
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karlos³
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Oops sorry I was half asleep when answering, I should have left it for today(and then better said nothing, because I can't really add anything to it,
now that I read it all awake and such...).
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clearly_not_atara
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I don't think HNO2 is blue... or likely to dissolve in butanone. More likely, you had N2O3 form and dissolve in the butanone. But you would need
enolization to get a rxn going! Usually this means protonating (or deprotonating) butanone. A little concentrated HCl is more acidic than a lot of
dilute HCl as you are well aware. I don't think butanone would get protonated under your stated rxn conditions; do you?
Also, if you are using a strongly acidic aqueous solution, you risk hydrolysing the oxime, although I am not sure how much of an issue this is in
practice. But it could mean that you produce diacetyl (not oxime) which does not precipitate as expected.
[Edited on 04-20-1969 by clearly_not_atara]
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Fery
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| Quote: Originally posted by clearly_not_atara | | Also, if you are using a strongly acidic aqueous solution, you risk hydrolysing the oxime, although I am not sure how much of an issue this is in
practice. But it could mean that you produce diacetyl (not oxime) which does not precipitate as expected. |
I did hydrolysis of different oxime (carvoxime->carvone) at pH 0,7 using solution of oxalic acid (approx 10 % wt)
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
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Boffis
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I agree with c_not_a that the blue solution is N2O3 in the immiscible layer of butanone which has formed under acid conditions. Its difficult to get a
high HCl concentration when you are trying to get butanone and sodium nitrite into a homogeneous solution. In basic conditions the nitrite is going to
sit there as quite inert nitrite ions. When this reaction is carried out with basic conditions the they use alkyl nitrites so we are back to the
original method. Using THF as a co-solvent may help by reducing the water content and thereby increasing the effective HCl concentration.
Either way I am fairly convinced that the butanone reaction doesn't work in a purely aqueous medium.
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