600538411
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Phenylalanine + 5N NaOH -> Benzaldehyde
It was once suggested to me that phenylalanine is suseptable to highly alkaline environments and that if one added phenylalanine to a 5N NaOH solution
and heated for 5 hours at 110-115 deg C, phenylalanine would degrade to form benzaldehyde...
Anyone tried or heard of a procedure for this? SWIK tried to do it twice without success (a. No bi-layer appears - may be related to large amount of
precipiatate & b. method of isolating benzaldehyde is proving difficult - solvent extraction? Filtering & separate by boiling points?)
Seems to be a major stumbling block for SWIK and if I could help them out it would be greatly appreciated...
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trilobite
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I'd try a few things. There is the possibility that benzaldehyde is formed, after which a side reaction is possible, the Cannizzarro reaction
where two molecules of benzaldehyde disproportionate into benzyl alcohol and benzoic acid.
One possibility is to first acidifiy the reaction mixture, maybe filter, then do a solvent extraction, wash the solvent with NaHCO3 solution. After
this the benzyl alcohol and benzaldehyde would remain in the organic solvent, the benzoic acid in the NaHCO3 washes as a salt. Acidifying these washes
should free the benzoic acid, drying and evaporating the organic solvent should give you benzyl alcohol and benzaldehyde. Benzaldehyde steam distills
but benzyl alcohol does not, it's also possible to separate them by washing with a sodium bisulphite solution and treating the NaHSO3 solution
with NaHCO3 to free the benzaldehyde from it's addition compound.
So, this is how it should be possible to find out if the reaction gives any products at all. I wouldn't be surprised if it gave only benzoic acid
and benzyl alcohol if anything at all. Then I'd try performing the reaction by steam distilling out the benzaldehyde as it is formed. Just
perform the reaction in a distillation apparatus and add water from an addition funnel to keep the volume of the reaction mixture constant. The
benzaldehyde can be extracted from the distillate if there is any, you can't miss the aroma. Here is a patent where they use steam distillation
in a similar fashion (BzH is for benzaldehyde):
Benzaldehyde.
Benedetti, C. O.; Vanselow, A. P.; Vanselow, W.
US1405261
Abstract
Benzyl chloride is hydrolyzed to benzyl alc. by refluxing with NaOH soln. for several hrs. and the reaction product is then gradually treated with
NaOCl contg. not over 2-3% NaOH and the BzH formed is distd. off at the same time by steam distn.
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