Chemistry Reference
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acting on chiral molecules. With this in mind, predict the product resulting from the E2
elimination of HBr when the illustrated isomer of 4-bromo-3-methyl-2-pentanone is
treated with sodamide. Show all stereochemistry and explain your answer.
In order to approach this problem, we must first identify the structure of the starting com-
pound when the acidic proton is oriented trans-periplanar to the bromide. The relevant
configuration is illustrated below and can be visualized using molecular models.
Realizing that the two methyl groups are oriented as projecting out of the same side
of the molecule, E2 elimination of HBr can only form a product with the methyl
groups cis to one another. The formation of this product is illustrated below using
arrow pushing.
6. Based on the answer to Problem 5, predict the product of the following reactions and
show all stereochemistry:
Aligning the acidic proton with the bromide in a trans-periplanar orientation allows for-
mation of the illustrated product as shown using arrow pushing.
