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Topic: Are N-oxides stable in aqueous alkaline solution?  (Read 3105 times)

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Offline _Espard_

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Are N-oxides stable in aqueous alkaline solution?
« on: March 30, 2015, 02:38:30 PM »
Pretty straightforward question, but I can't seem to find much of a direct answer.

Are N-oxides (i.e. pyridine-N-oxide, N-methylmorpholine-N-oxide) stable in aqueous alkaline solution?

Offline Sir_Goat

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Re: Are N-oxides stable in aqueous alkaline solution?
« Reply #1 on: March 31, 2015, 07:42:46 AM »
I guess another sensible question to ask is what would happen in acidic solutions? My guess would be that the oxygen would be protonated and become a leaving group, leaving you with, for example, just pyridine.

So I guess it depends how alkaline your solution is? The more H+ available the less stable the compounds.

Seems logical to me anyway but I guess this would explain why there there's no obvious straightforward answer: It depends on the pH of your solution.

Offline Dan

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Re: Are N-oxides stable in aqueous alkaline solution?
« Reply #2 on: March 31, 2015, 08:04:13 AM »
My guess would be that the oxygen would be protonated and become a leaving group, leaving you with, for example, just pyridine.

No, that would give you Py2+, which won't happen. To get pyridine from pyridinium N-oxide you need nucleophilic abstraction of O - i.e. the Py is the leaving group, not hydroxide/water.

I'd guess that SNAr reactions (for example with hydroxide: pyridine N-oxide :rarrow: 2-pyridone) would be a more likely degradation pathway - but I don't know the answer to the OP's question.
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Offline orgopete

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Re: Are N-oxides stable in aqueous alkaline solution?
« Reply #3 on: April 02, 2015, 07:37:07 PM »
Re posters original question. I'd expect the N-oxides to be reasonably stable. If pyridine-N-oxide were dissolved in water and made basic, I wouldn't expect anything to happen. Did something happen?
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