fusso
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Want to make dimethylglyoxime, works with hydroxylamine?
Not sure if this was asked before.
I have most reagents needed for making DMG from MEK, but I don't have hydroxylaminemonosulfonate, instead I have hydroxylamine sulphate. Will it work?
Edit: plz provide procedures which start from MEK.
[Edited on 190324 by fusso]
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Boffis
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This procedure is in Vogel's Textbook of organic chemistry 3rd ed for certain and possibly in the 5th ed too. Both editions are available from the
internet. The procedure used butyl nitrite/HCl and MEK to give the monoxime and then this is reacted with hydroxylammonium chloride or sulphate and a
base. You don't need to isolate the intermediate monoxime and the butyl nitrite can be made easily from the alcohol and sodium nitrite in high yield
just before use without any need to purify it by distillation.
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UC235
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http://www.orgsyn.org/Content/pdfs/procedures/CV2P0204.pdf
I've done this two ways. Using methanol to make a methyl nitrite gas generator and using premade isopropyl nitrite added to the reaction via addition
funnel. It worked both times.
The hydroxylaminemonosulfonate isn't stable. It's something you make fresh from sodium nitrite with sulfite reduction. If you have hydroxylamine
already made, there's nothing to stop you from just using that, but some don't have that luxury or would like to save it for something else. I used
sodium metabisulfite instead of preparing anything fresh and got a good yield.
If you decide to try to isolate the Diacetyl Monooxime, DO NOT LET THE STEAM DISTILLATION GET LOW ON WATER. Diacetyl monoxime violently decomposes
when heated. I thought I still had some water but the stillpot suddenly heated up dramatically and the the stuff filled my entire distillation
apparatus with carbon foam. I remember charred/carmelized smelling steam jetting out of the vacuum adapter. It's a miracle nothing broke and it took a
ton of scrubbing to get clean.
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fusso
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Other than alkoxides, what catalysts can I use? Does acids work? I don't have any alkali metals. Strongest bases I have are hydroxides.
[Edited on 190408 by fusso]
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Boffis
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Read and thou shall be enlightened
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fusso
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@boffis ?
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Rhodanide
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I believe there's already a detailed procedure thread on here already. Iirc its author is Magpie.
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Waffles SS
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Quote: Originally posted by UC235  |
The hydroxylaminemonosulfonate isn't stable. It's something you make fresh from sodium nitrite with sulfite reduction. If you have hydroxylamine
already made, there's nothing to stop you from just using that, but some don't have that luxury or would like to save it for something else. I used
sodium metabisulfite instead of preparing anything fresh and got a good yield.
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May i know procedure that you used for making hydroxylaminemonosulfonate from sodium metabisulfite and sodium nitrite?
Chemistry = Chem + is + Try
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UC235
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| Quote: Originally posted by Waffles SS | | Quote: Originally posted by UC235 |
The hydroxylaminemonosulfonate isn't stable. It's something you make fresh from sodium nitrite with sulfite reduction. If you have hydroxylamine
already made, there's nothing to stop you from just using that, but some don't have that luxury or would like to save it for something else. I used
sodium metabisulfite instead of preparing anything fresh and got a good yield.
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May i know procedure that you used for making hydroxylaminemonosulfonate from sodium metabisulfite and sodium nitrite? |
Open the orgsyn link and follow the procedure under part C. Metabisulfite technically has a higher SO2 content than the bisulfite they use, but not by
much. The difference is about 10%. I'd just go ahead and use the full amount of metabisulfite as "technical bisulfite" to account for uncertainty in
purity.
I had my procedures confused. I have also run a modified version of this procedure using metabisulfite: http://orgsyn.org/Content/pdfs/procedures/cv1p0318.pdf
This one calls for fresh bisulfite made with SO2. I swapped the easier prep from the dimethylglyoxime procedure without issue.
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fusso
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But why nitrite ester selectively react with ethyl part of MEK, instead of methyl?
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UC235
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Because in the presence of acid catalyst, the internal enol (thermodynamic) is pretty much the only one formed. Enol C=C double bond does a
nucleophilic attack on electron poor nitrogen from the nitrite. I expect that the active species is actually NO+ or NOCl and the ester (which
hydrolyzes in the presence of acid) is just a convenient means to add nitrite at a slow rate to the reaction mix.
If you want to make the kinetic enol and attack the methyl group, you need to do something like use Lithium Diisopropylamide at dry ice temperatures,
add a source of NO+, and warm to room temp.
[Edited on 13-4-2019 by UC235]
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