Answers to Practice Questions Chapter 8

8.1 Show elimination product of the following reactions.


(2S, 3R)-2-bromo-3-phenylbutane in the presence of CH3ONa/CH3OH produces (z)-2-phenyl-2-butene



The anti coplanar conformation of H and leaving group OTs is shown more clearly in the chair conformation of the cyclohexane. Please note that the other β-H can not be anti to the leaving group OTs. Also, in order to fit to the anti coplanar requirement, both H and OTs have to be in axial positions, so this conformation is the one that undergoes the elimination although it is not the most stable one. Since the most stable conformation does not fit the E2 stereochemistry requirement, so the elimination has to go through the less stable conformation. Heat is preferred to facilitate the reaction.


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