(Hive Addict)
04-25-03 06:10
No 429324
(Rated as: good idea!)
This is a quite useful method to generate the bisulfite-adduct from impure aldehydes or ketones.
Dissolve the impure carbonyl compound in a equal volume of toluene or DCM and add 1-5 mol% PTC (my choice is aliquat 336). To this solution add 1.5-2 molar equivalents sodium bisulfite [1] as a 25% aqueous solution and stir the crap out of the mixture for 30 minutes at room temp [2]. Filter off the precipitated bisulfite-adduct and continue the stirring for another 30 minutes. Repeat until no more adduct precipitates out. Rinse the adduct once with 70% IPA to remove any remaining toluene. The yields are close to quantitative.
[1] Carbonyl compounds can be scarce and very expensive while sodium bisulfite is cheap. To get high yields of the adduct use excess of bisulfite.
[2] If the precipitation doesn't start within 30 minutes at room temp, heat the mixture to 50-60°C and continue the stirring.
Edit: It looks like this method has been patented already. Patent US4162269 [pdf]
Freaky
(Hive Bee)
04-25-03 11:38
No 429370
Wow! Excellent find! So, does this render vacuum distillation of MDP2P optional?
1) Atmospheric Distillation of safrole
2) Isomerization of Safrole
3) Performic/Peracetic oxidation of isosafrole
4) Workup to MDP2P
5) Using the above method to purify MDP2P
6) Al/Hg reductive amination of above to get product
If so, then this would greatly help bees without a good vacuum source!
(Chief Bee)
06-04-03 16:15
No 437837
Not completely, especially not if you use the wacker oxidation to make your MDP2P. A common byproduct is MD-Phenylpropanal (also called "MDP3P"), and as this also will form a bisulfite adduct, you cannot remove that with this procedure. All impurities with a carbonyl function (aldehydes/ketones) will form bisulfite adducts (piperonal and MD-Phenylacetaldehyde are other examples).