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Topic: Isolating 2,2'-bipyridyl N,N'-dioxide from reaction mixture  (Read 3368 times)

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Offline virus

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Isolating 2,2'-bipyridyl N,N'-dioxide from reaction mixture
« on: March 28, 2008, 03:09:57 PM »
I am doing a lab project in which I am synthesizing an organic ligand to make molecular Borromean rings.
This is the actual compound I am trying to make - http://en.wikipedia.org/wiki/Molecular_Borromean_rings

The first reaction is oxidation of 2,2'-bipyridine to make the N,N'-dioxide. I have found a couple of publications on how to do it. Peracetic acid is one way and the mixture of acetic acid/H2O2 is the other, which as far as I get is the same because the second method generates the peracetic acid in situ.

The real problem is the isolation/purification part. The remaining Peracetic acid, acetic acid, H2O2 and H2O can all be distilled away, hopefully without blowing it all up :D But the N,N'-dioxide would still be as acetic salt, right? In analogous reaction with pyridine n-oxide (from orgsyn.org) they distilled it under 1mmHg to remove the associated acetic acid. But this would most likely not be possible with bipyridine.
Could it be as simple as neutralization with Na2CO3 or NaHCO3 and then recrystallization from water?
This is my first practical experience with N-oxides so any suggestions are welcome.

Offline agrobert

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Re: Isolating 2,2'-bipyridyl N,N'-dioxide from reaction mixture
« Reply #1 on: March 28, 2008, 06:28:11 PM »
I would first of all use TFA (trifluoroacetic acid) and H2O2 to generate the peroxy species.  Then monitor your reaction by TLC and when finished add a few mLs of a saturated sodium bisulfite solution.  This will kill any peroxy species and generate SO2 which is a smelly toxic gas (caution).  You will be left with your product, TFA, water and some salts of course but TFA has a lower bp than acetic and should come off under reduced pressure.
In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

Offline virus

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Re: Isolating 2,2'-bipyridyl N,N'-dioxide from reaction mixture
« Reply #2 on: March 29, 2008, 04:38:51 AM »
Thank you for your suggestions, especially for that bisulfite.
The really confusing stuff about n-oxides for me is their (in)ability of forming salts with acetic acid. How stable are these salts? And how do I turn them into the pure substance?
Like I said, pyridine n-oxide acetate was turned into pure pyridine n-oxide by strongly heating it under reduced pressure. But is this the only way?

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