From: Alejandro Lalo (cocoroc9$##$yahoo.com)
Date: Fri Oct 27 2000 - 16:43:05 EDT
Dear members: I have to synthesize the compound
beta-bromostyrene from 2,3-dibromo-3-phenylpropanoic
acid. The acid exists as a pair of enantiomers (2R,3S)
and (2S,3R). The reaction between the
2,3-dibromo-3-phenylpropanoic acid and anhydrous
potassium carbonate and heat in pure butanone gives
only the Z-beta-bromostyrene and the reaction with
aqueous sodium carbonate and heat gives the
E-beta-bromostyrene as a major product and the
Z-beta-bromostyrene as a minor product. I need to know
the mechanisms of the reactions described above. I
know that both reactions are decarboxylative
eliminations but I don't know the exact mechanisms and
I didn't find them in the literature. My question is:
Why in the presence of pure butanone in anhydrous
conditions the only product is the Z isomer and why in
water the major product is the E isomer of the
beta-bromostyrene? I need to know the complete
mechanism of both reactions.
Any of you can help me?
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