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Author: Subject: Vanillin bisulfite adduct
monolithic
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[*] posted on 11-9-2020 at 05:05
Vanillin bisulfite adduct


I recently bought a rather large amount of vanillin. The container it came in isn't very air-tight and I'm concerned about oxidation because I don't plan on using hundreds of grams any time soon. I want to purify this vanillin and make it stable for long-term storage.

Is there an easy method for preparing the bisulfite adduct of vanillin?

Apparently the adduct of vanillin is water soluble, unlike many other aldehyde bisulfite adducts. This means the usual bisulfite adduct procedure doesn't work, where the adduct precipitates out as a solid and one simply vacuum filters away the non-aldehyde impurities.

I did some searching and I couldn't find much other than a chemplayer post saying the vanillin adduct is water soluble, and a few inconclusive posts by Sedit. Maybe form the bisulfite adduct and then wash away the vanillic acid with ethyl acetate? Would this have the intended effect?
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Tsjerk
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[*] posted on 11-9-2020 at 06:18


See example 1.

Yes, dissolving the vanillin in NaHSO3 and washing it with something apolar should work.
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S.C. Wack
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[*] posted on 11-9-2020 at 13:05


Solubility has a lot to do with concentration but it makes no sense to purify a nicely crystalline material by converting it to a less nicely crystalline material...I wonder if it can be extracted from 5% NaOH with e.g. ether.



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monolithic
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[*] posted on 11-9-2020 at 15:09


Quote: Originally posted by S.C. Wack  
Solubility has a lot to do with concentration but it makes no sense to purify a nicely crystalline material by converting it to a less nicely crystalline material...I wonder if it can be extracted from 5% NaOH with e.g. ether.


Quote:
In water >2%; in ethanol is 1:2 vanillin:ethanol. Freely soluble in chloroform, ether, in solutions of fixed alkali hydroxides; solutions in glycerin and hot water.


https://pubchem.ncbi.nlm.nih.gov/compound/Vanillin#section=S...

I thought about this too but I'm not sure if it would work. I guess I can try this weekend since I have some NaOH and chloroform on hand. The advantage of storing it as the bisulfite adduct is that I don't have to worry about it readily oxidizing to the carboxylic acid. :)

[Edited on 9-11-2020 by monolithic]
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Pumukli
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[*] posted on 12-9-2020 at 09:47


Actually, how easily would vanilline be oxidized by air at room temp? Have anyone seen it described in a paper somewhere? Just curious.

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DraconicAcid
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[*] posted on 12-9-2020 at 10:05


Quote: Originally posted by S.C. Wack  
Solubility has a lot to do with concentration but it makes no sense to purify a nicely crystalline material by converting it to a less nicely crystalline material...I wonder if it can be extracted from 5% NaOH with e.g. ether.


Vanillin is a phenol, and will form a phenoxide in NaOH.




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Boffis
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[*] posted on 12-9-2020 at 11:11


Vanillin is very resistant to oxidation under any conditions. It seems that the more complex hydroxyaldehydes are resistant for some reason.
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monolithic
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[*] posted on 13-9-2020 at 04:40


Quote: Originally posted by Boffis  
Vanillin is very resistant to oxidation under any conditions. It seems that the more complex hydroxyaldehydes are resistant for some reason.


I did not know that, I assumed it readily oxidized.
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