organicmadness
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N-methylformamide problem, can any brains solve??
To all Organic chemists, which one of you has the brains to figure out this one?
So I was doing my research into N-methylformamide, and realised that there are two forms that exist. One boils at 180-185 degrees, and the other boils
at 199-201 degrees.
With reference to the N-meth that boils at 199-201:
There are two resonance structures. There is a partial double bond that exists between the carbonyl carbon and the nitrogen which gives rise to a high
rotational barrier. This molecule is not able to rotate around its main axis. The positive charge on the nitrogen is due to the double bond, which
makes it useless to work with.
Something has been done to the higher boil point nmf that keeps it in the non active state. For it to react, the nitrogen needs to have a spair pair
of electrons, which it doesn't.
Is there a way to reverse this to get to the 180 degree boiling point n-methylformamide FROM the 199-201 degree n-methylformamide?
NB:
The reaction used from the industrial company to create the 199-201 N-methylformamide:
Methylamine (CH5N) + Methyl formate (C2H4O2) ----->
N-methylformamide (C2H5NO) + Methyl alcohol (CH4O)
[Edited on 14-6-2013 by organicmadness]
[Edited on 14-6-2013 by organicmadness]
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ScienceSquirrel
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Do you have any references?
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KrysHalide
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Seems like archaic alchemie to me.. There can't be two "forms" of the same molecule, except for enantiomeres.. Which isn'rt the case here.
There are tautomeric forms, but these are in equilibrium. You cannot seperate one form from the other, so IMHO, there no "active" N-methylformamide vs
"inactive" N-methylformamide.
All there is N-methylformamide, which can tautomerize in two different formal representations, the "enolate like" and the carbonyl form.
Please prove otherwise
A hydrated derivative might account for seperate bp, but then again we are not talking of the same molecule.
[Edited on 14-6-2013 by KrysHalide]
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O Icarus of the fearless flight
For the greatest tragedy of them all
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Dr.Bob
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I concur, there are not two isomers of N-methylformamide. N-methylformamide has a BP of ~200C. Not sure what the other material might be, but it
is not N-methylformamide.
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Nicodem
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Thread Moved
14-6-2013 at 11:49 |
Nicodem
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Quote: Originally posted by organicmadness  | | So I was doing my research into N-methylformamide, and realised that there are two forms that exist. One boils at 180-185 degrees, and the other boils
at 199-201 degrees. |
Seriously? Two liquid forms of the same compound? And you don't even bother to give the reference for this extraordinary thing?
| Quote: | | With reference to the N-meth that boils at 199-201:There are two resonance structures. There is a partial double bond that exists between the carbonyl
carbon and the nitrogen which gives rise to a high rotational barrier. This molecule is not able to rotate around its main axis. The positive charge
on the nitrogen is due to the double bond, which makes it useless to work with. Something has been done to the higher boil point nmf that keeps it in
the non active state. For it to react, the nitrogen needs to have a spair pair of electrons, which it doesn't. |
Sounds like you might be trolling, but just in case you are serious: Formamides do not form stable rotamers (atropisomers). Their rotamers
interconvert easily at way bellow their boiling point. And resonance structures have nothing to do with isomeric substances - they are only a
pedagogic tool to teach students the bond delocalization.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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KrysHalide
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Detritus?
Never regret thy fall,
O Icarus of the fearless flight
For the greatest tragedy of them all
Is never to feel the burning light.
Oscar Wilde
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wackojacko
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The Merck indeax states bp of 180-185 yet once checked various companys MSDS they vary some are 180-185 while others are 199-201 both CAS 123-39-7
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wackojacko
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also i have a friend who tried both the 180-185 and 199-201 with p2p and only the 180-185 worked
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wackojacko
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could it be that they have treated it to concerve the double bonded nitrogen???
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unionised
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Which is more likely?
A mistake in recording the BP, or a weird situation where one liquid has two boiling points?
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organicmadness
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None of the information has been really helpful. The question is not whether or not resonance structures exist.
There are for a fact, two forms of n-methylformamide that exist in the industrial industry. Take my word for it. Some manufacturers sell the nmf that
boils at 199-201. And others the one that boil at 180-185.
The 199-201 definitely DOES NOT work or react.
My question is, does anyone know a way of potentially changing the nmf that boils at 199-201 TO 180-185?? That is the question...
Any brains?
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AndersHoveland
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| Quote: Originally posted by Nicodem | | Formamides do not form stable rotamers (atropisomers). Their rotamers interconvert easily at way bellow their boiling point. |
I do not know if this is true. Nicodem, are you absolutely sure about this?
The structure of formamides contains a somewhat delocalized bonding, since they are electron-donating. In fact, it would be more accurate to draw a
diagram with the double bond between the carbon and nitrogen atom, with a positive charge on the nitrogen and a negative charge on the oxygen atom.
Assuming Nicodem was wrong, this could potentially prevent rotation, and there would be two stereoisomers (presumably one configuration with the
oxygen pointing out 60 degrees away from the methyl group, and the other with the oxygen atom pointing away).
I have never read anything about this before. However, if there were two forms of the compound, I would think that the way to interconvert
them would be to use a non-nuceophilic base like N,N-Diisopropylethylamine.
[Edited on 16-6-2013 by AndersHoveland]
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watson.fawkes
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From the end of this page: | Quote: | | Thus, the barrier to rotation about the NH2–CHO bond in formamide is over 18 kcal/mol, and the CH3NH–CHO bond in N-methylformamide is more than a
kcal/mol greater. Such barriers permit the observation of conformational isomers of amides by room temperature nmr. For simple amides like
N-methylacetamide and the formamides noted above, the trans conformer is more stable than cis by more than 1.5 to 2.5 kcal/mol.
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organicmadness
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The only way that makes sense is a nucleophilic attack on the carbon which would drive the double bond back to nitrogen. Would sodium acetate as a
strong conjugate base work?
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Crowfjord
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Organicmadness, if you want anyone to take you seriously on a science forum, please provide a reference. Why should anybody just "take your word for
it"?
If what you say is true though, I figure the higher boiling variety is merely impure, resulting in boiling point elevation (freshman chemistry). All
the formamides have partial double bond character at the C-N bond, giving a planar shape to the molecule and a rotational barrier, just as stated by
the reference given above by watson.fawkes.
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GreenD
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Not sure but it would seem to me pure formamide would be the lower bp, while the higher is a solution of formamide/n-methyl
formamide.
I can't find that there is an azeotrope, but... maybe.
ʃ Ψ*Ψ
Keepin' it real.
Check out my new collaborated site: MNMLimpact.com
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