SunriseSunset
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Hofmann rearrangement Question
https://www.youtube.com/watch?v=ihvqdULWklY
The question is...
If the amide was not water soluble, would one be able to use ethyl alcohol or methylene chloride in substitute to dissolve it and proceed with
everything else as normal? What would the implications be? If any.
Why do chemists call helium, curium and barium the medical elements?
because if you cant helium or curium, you barium! - Heimerdinger
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User123
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You cannot use ethanol for obvious reasons of it reacting with a reagent.
Do you have to have a stupid self important animated signature on all of your posts? It is a science forum. No one else has one. It lowers the tone.
[Edited on 16-12-2015 by User123]
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elementcollector1
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Literally all the high-post-count members have signatures.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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User123
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Good for them. They lower the tone too. Do you really think anyone gives a damn how many elements you have collected? They don't.
[Edited on 16-12-2015 by User123]
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SunriseSunset
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Sorry, I forgot to take that off from a while ago when some other people said the same thing.
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SunriseSunset
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Quote: Originally posted by User123  | You cannot use ethanol for obvious reasons of it reacting with a reagent.
[Edited on 16-12-2015 by User123] |
That confirmed a suspicion I had.
Does anybody have experience with this
I feel like if the amide was dissolved in a nonpolar solvent, it would actually decrease the possibility and rate for the reaction to occur. So I'm
assuming the best bet would be to just put stirring on full blast and except possibly a longer time to completion. Am I correct?
I'll experiment around and report back how it goes... It's a shame that an alcohol wouldn't work. I wish I had TLC sheets. Someone buy me TLC sheets
for the holiday ^_^
[Edited on 16-12-2015 by SunriseSunset]
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User123
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There are plenty of examples of carbamate formation in non aqueous solvents. What reagent are you using? Or what do you have available? Perhaps you
could use a phase transfer catalyst with a DCM layer and an aqueous layer, if your substrate is insoluble in water.
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elementcollector1
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Huh. Strange, it seems like someone changed this entire topic.
Anyway, you know what really brings down the content of a forum? Flaming posts like yours that attack others for no reason. Fascinating how you'll
ignore that, by the way.
Elements Collected:52/87
Latest Acquired: Cl
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UC235
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I mean you _can_ run a Hoffman rearrangement in an alcohol solvent. You just can't use bleach. And you get a carbamate as a product. http://www.orgsyn.org/demo.aspx?prep=v78p0234
It is also possible to isolate the intermediate isocyanate itself by running the reaction in a biphasic system. I have a reference for this somewhere,
but can't find it at the moment.
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SunriseSunset
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Reporting back!
With using as-close-as possible to stoichiometric quantities of the Oleamide and Bleach (6.0% hypochlorite) were added together and mixed inside a
tiny 3-neck RBF.
RXN Heated in a hot water bath to slowly bring to 50*C and aqueous potassium hydroxide was drained from addition funnel.
Once the solid completely dissolved finally, the rxn temperature was raised to 70*C and was held at 75*C for 30min.
Then taken off of the hot water, and allowed to cool to room temp. Extracted with dichloroethane, dried with anhydrous MgSO4 and filtered very
thoroughly.
solvent was boiled down under a rather strong vacuum aspirator to leave a mustard colored oily solid. Put in a vacuum drying desiccator for 42 hours
and weighed to find a yield is 41% molar. 
Is adding gelatin powder for the rxn necessary when using different amides that are not Urea? If so, would does it increase the yield?!
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byko3y
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Notes - A Re-examination of the Limitations of the Hofmann Reaction
New strategies for the Hofmann reaction
I have both those articles, but I'm not sure whether I should upload them.
A regular hofmann still works for long chain acids, it just gives poor yields (20-40%).
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SunriseSunset
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It would be nice if you could upload them. I could probably find them, but you'd save me the trouble :] If you don't mind.
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