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Topic: Purification of benzaldehyde.  (Read 9340 times)

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Offline dudeman

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Purification of benzaldehyde.
« on: December 15, 2013, 06:32:12 PM »
I'm simply speculating a possible method of purifying benzaldehyde. I don't have any...

I've read on other forums that the bisulfite adduct of benzaldehyde is destroyed in alkali solution. From what I read the benzaldehyde is liberated and floats on top of the basic solution.

The question that puzzles me is this... Sodium metabisulfite is used to form the adduct. So when the adduct is added to the alkali solution and it is broken apart. Does the sodium metabisulfite convert into something else?

The benzaldehyde is reportedly neutral meaning no basic compounds are dissolved. There is the possibility that sodium metabisulfite is dissolved since it is neutral too.

Would washing the liberated benzaldehyde with h2o remove any bisulfite contamination?

Could this be done before the benzaldehyde is oxidized heavily?

Offline dudeman

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Re: Purification of benzaldehyde.
« Reply #1 on: December 15, 2013, 10:52:23 PM »
Can a scientist please answer my questions?

Offline orgopete

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Re: Purification of benzaldehyde.
« Reply #2 on: December 15, 2013, 11:59:02 PM »
This is a pretty broad question. Personally, I'd just buy it. It would have been too cheap compared to my labor to purify it. Since the question is asking about a pretty crude purification method, I would suggest just dissolving it in ether and washing out the benzoin acid with bicarbonate.
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Offline clarkstill

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Re: Purification of benzaldehyde.
« Reply #3 on: December 16, 2013, 11:18:32 AM »
Dissolve it in DCM and wash it with aq. sodium bicarbonate (to remove the majority of benzoic acid).  Then distil it.  Easy peasy.

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