Random
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Nitroacetone
I seen a synthesis of 2,5-dimethylpyrazine starting from acetone forming nitroacetone with propyl nitrite (which I don't have so I would use NO2 gas
bubbling to acetone).
Is nitroacetone dangerous like toxic, explosive or something like that? I don't want to be poisoned and killed by explosion.
The synthesis then continues with reduction to aminoacetone, self condensation of aminoacetone and oxidation of the product to 2,5-dimethylpyrazine.
It is strong cocoa/chocolate smell as I read on one site which lists flavor compounds.
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AndersHoveland
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No, nitroacetone is not explosive. As for its toxicity, I am not sure. While 2-nitroacetic acid is very poisonous can can be aborbed through skin, I
do not think nitroacetone is very poisonous, although it is much more volatile.
Please share (or provide a link to) the synthesis you have seen of nitroacetone, I am hoping it is easier than the two I am aware of. Are you saying
nitroacetone can be prepared from acetone and propyl nitrite? Propyl nitrite may be easily prepared from cold isopropanol, sodium nitrite, and
hydrochloric acid. The nitrite ester easily separates out. For detailed information about the preparation of isopropyl nitrite with pictures see: http://www.shadowrx.com/forums/showthread.php?t=933
Nitroacetone may be extracted with ether, and has a normal boiling point of 152 degC, or 105 degC at 25mmHg (reduced pressure). Nitro acetone has a
melting point between 46-50 degC. When care is taken to obtain the pure product, the melting point tends to be close to 49 degC.
Solid nitroacetone is unstable in air, but it is stable as an ether solution away from prolonged exposure to sunlight. Nitroacetone slowly hydrolyzes
with water.
The route to nitroacetone with which I am already familiar is:
25g nitropropanol and 37.5g sodium dichromate are mixed in 25mL water. 35mL of 60% sulfuric acid are then slowly and periodically added to the
solution over a period of 4 hours, keeping the temperature below 14 degC at all times.
A dark green crystalline substance was then extracted from the solution using ether. Crystals of nitroacetone form after the ether evaporates. The
crystals are then recrystallized from methanol (to give a purer product). The resulting nitroacetone from this procedure melts at 46 degC.
The nitropropanol which the above procedure refers to is 1-nitropropan-2-ol, which can be prepared by limited nitroaldol reaction of acetaldehyde with
nitromethane (in the presence of a base). I thought I had the synthesis somewhere on my site, but now I cannot find it. Note that you would not
want to use 2-nitropropanol.
[Edited on 25-5-2011 by AndersHoveland]
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Nicodem
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Quote: Originally posted by Random  | | I seen a synthesis of 2,5-dimethylpyrazine starting from acetone forming nitroacetone with propyl nitrite (which I don't have so I would use NO2 gas
bubbling to acetone). |
If alpha-nitroketones could be made that way, it would be well known, because the reaction of alkyl nitrites with ketones under acidic catalysis is
widely used for the alpha-nitrosation of ketones to give alpha-oxo-oximes (RCOC(=NOH)R). If you have a reference that claims otherwise, please provide
it!
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AndersHoveland
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Of course, it is possible to oxidize the CH3C(=O)CH=NOH to nitroacetone;
"...anhydrous solutions of peroxytrifluoroacetic acid... can be used to oxidize aldoximes to nitroalkanes in good yields. Ketoximes fail to react in
these conditions and are cleaved to the parent carbonyl compounds." source: http://www.sciencedirect.com/science/article/pii/S0040403900...
[an aldoxime is CH3CH=NOH ; a ketoxime is CH3C(=NOH)CH3 ]
A widely used reaction for the conversion of oximes to nitroalkanes involves the following reactions:
1. treat the oxime with chlorine or bromine (followed by treatment with sodium bicarbonate) to form an a-bromonitrosoalkane
R2CBr(NO).
2. oxidation of the resulting nitroso group (using nitric acid, hydrogen peroxide, or supposedly even oxygen in the air) to a nitro group.
R2CBr(NO2)
3. reduction of the a-halonitroalkane (with either sodium borohydride, or with a mix of potassium hydroxide in ethanol) to the final nitroalkane
R2CH(NO2). As to how the KOH-ethanol can reduce the compound, I think the nitrogroup acts as an electron-withdrawing group so that the reaction with a
hydroxide ion puts the hydroxide on the bromine atom, forming hypobromous acid, which then attacks the ethanol in a haloform reaction.
I finally found the reference of the reaction of ethyl nitrite with ketones: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2...
It states that CH3CH2C(=O)CH3 and CH3CH2ONO react (in the presence of HCl) to form CH3C(=O)C(=NOH)CH3. Note that this is a ketoxime, not an
aldoxime, so it might not necessarily work as well for converting acetone to CH3C(=O)CH=NOH, as you may have hoped. Aldoximes are much more reactive,
and I think that a nitrolic acid would likely form instead with all the nitrous acid floating around.
Although I did find this:
Ketones can react with nitrous acid (obtained from amyl nitrite and gaseous hydrochloric acid, the ketone being dissolved in acetic acid) to form
isonitroso-ketones,
RC(=O)CH=NOH
(L. Claisen, Ber., 1887, 20, pp. 656, 21 9 4).
[Edited on 25-5-2011 by AndersHoveland]
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Random
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Thanks for the alternative synthesis of nitroacetone. 
http://www.springerlink.com/content/g110355g1325173x/
Here is reference for syntheis of 2,5-dimethylpyrazine starting from acetone forming nitroacetone and then redutcion with Sn/HCl to yield
aminoacetone.
http://sites.google.com/site/energeticchemical/exeriments
This is reference to synthesis of nitroacetone from acetone and NO2.
Nitroacetic acid could be toxic like chloroacetic acid, while it's salts aren't toxic. Though chloroacetone is like tear gas, I hope nitroacetone
isn't like that.
Maybe I made mistake, is CH3COCH=NOH nitroacetone or oxime?
Edit:
Now I see, it could be that alpha-oxo-oxime. It looks I actually don't need nitroacetone, though, If I can form aminoactone from nitroacetone, it can
still be useful as I actually need aminoacetone.
[Edited on 25-5-2011 by Random]
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AndersHoveland
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That "reference" is my site, and I can tell you that nitroacetone from nitrogen dioxide being bubbled into acetone is not a very
practical method of preparing nitroacetone! There was a very strong smell of acetic acid afterwards. And yes, the fumes from the reaction are the same
as tear gas, even wearing goggles! I also made the mistake of adding hydrochloric acid to the acetone to promote tautomerization (and thus faster
reaction rate). This may have caused a Meyer reaction on the nitrogroups, greatly decreasing my yield. (Victor Meyer invented several reactions, I am
refering to the one where, for example, the aci-form of phenylnitromethane, (H5H6)CH2NO2, reacts in aqueous sulfuric acid at room temperature to form
phenylnitromethane and benzohydroxamic acid, (H5C6)C(=O)NHOH, the latter of which often hydrolyzes into benzoic acid and a hydroxylamine salt) also
note that the aci-form nitromethane, for example, is CH2=NO2[-] H[+].
Ketones can react with nitrous acid (obtained from amyl nitrite and gaseous hydrochloric acid, the ketone being dissolved in acetic acid) to form
isonitroso-ketones,
RC(=O)CH=NOH
(L. Claisen, Ber., 1887, 20, pp. 656, 21 9 4).
"When silver nitrite is agitated for 24 hours with a dilute ether solution of iodoacetone, the nitroacetone produced remains insoluble, while the
impurities dissolve ... amino acetone is obtained by reducing the nitroacetone, indicating it is not a nitrite."
Journal of the Chemical Society, Volume 78, Part 1, p82
For further information about NO2 reacting with unsaturated compounds, there is a long boring article you might read:
http://docs.google.com/viewer?a=v&q=cache:4f3U855Jn70J:p...
Although the original poster has realized that he does not need nitroacetone, perhaps a moderator would like to move this topic into the organic
chemistry section, the subject of nitroacetone really deserves better than the beginnings section.
[Edited on 25-5-2011 by AndersHoveland]
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ItalianChemist
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| Quote: Originally posted by AndersHoveland | No,
The route to nitroacetone with which I am already familiar is:
25g nitropropanol and 37.5g sodium dichromate are mixed in 25mL water. 35mL of 60% sulfuric acid are then slowly and periodically added to the
solution over a period of 4 hours, keeping the temperature below 14 degC at all times.
A dark green crystalline substance was then extracted from the solution using ether. Crystals of nitroacetone form after the ether evaporates. The
crystals are then recrystallized from methanol (to give a purer product). The resulting nitroacetone from this procedure melts at 46 degC.
[Edited on 25-5-2011 by AndersHoveland] |
Can potassium permanganate be used?
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AndersHoveland
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I am not sure, I think dichromate is a somewhat more selective oxidizing agent, you will probably get much lower yields with permanganate.
If you have access to the Journal of Organic Chemistry, you might see
ALIPHATIC NITRO KETONES
CHARLES D. HURD, MAY E. NILSON;
J. Org. Chem.; 1955; 20(7); 927-936,
which has a short description on the preparation of nitroacetone.
There is also an interesting, but confusingly worded article
"Synthesis ofα-nitrocarbonyl compounds"
K. K. Babievskii, V. M. Belikov and N. A. Tikhonova
http://www.springerlink.com/content/w48107v45086v883/
which I will try to summarize for you:
Complexes of dimethylformamide with dimethyl sulfate react with nitromthane in the presence of sodium ethylate (more commonly known as ethoxide), in
60% yield. The intermediate
(CH3)2NC(CH3)(OC2H5)2 reacts with nitromethane to form
(CH3)2NC(CH3)=CHNO2.
1.5 grams of the 2-[dimethylamino]-1-Nitropropylene,
(CH3)2NC(CH3)=CHNO2, is reacted dropwise with 15mL of 10% KOH. After 5-10 minutes, a white precipitate formed. The precipitate was separated by
filtration, washed on the filter with absolute(pure) alcohol and ether, then dried in a desiccator over KOH. The final product was 1.31g (81% yield)
of the potassium salt of nitroacetone. The potassium salt of nitroacetone decomposed between 190-191degC.
[Edited on 26-5-2011 by AndersHoveland]
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Random
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I have found a reaction for obtaining 2,5-dimethylpyrazine in Name reactions in heterocyclic chemistry II book.
Oxoaminoketone can be made in-situ with acetic acid and nitrite salt along with acetone. Then it can be reduced with zn/hcl, fe/hcl or anything other.
Cupric salt can be used for oxidation to obtain dimethylpyrazine.
Now I only have to prepare nitrite.
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Boffis
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@Random
Does the book you mention above have a reference to the in situ preparation of aminoketones via nitrosation with nitrite and acid? I would very much
like to see it.
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Random
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