The reaction of butan-2-ol with concentrated aqueous HBr goes with partial racemization, giving more inversion thanretention of configuration. Propose a mechanism that accounts for racemization with excess inversion.(b) Under the same conditions, an optically active sample of trans-2-bromocyclopentanol reacts with concentrated aqueous HBr to give an optically inactive product, (racemic) trans-1,2-dibromocyclopentane. Proposea mechanism to show how this reaction goes with apparently complete retention of configuration, yet withracemization. (Hint: Draw out the mechanism of the reaction of cyclopentene with Br2 in water to give thestarting material, trans-2- bromocyclopentanol. Consider how parts of this mechanism might be involved in thereaction with HBr.)
The reaction of butan-2-ol with concentrated aqueous HBr goes with partial racemization, giving more inversion than
retention of configuration. Propose a mechanism that accounts for racemization with excess inversion.
(b) Under the same conditions, an optically active sample of trans-2-bromocyclopentanol reacts with concentrated aqueous HBr to give an optically inactive product, (racemic) trans-1,2-dibromocyclopentane. Propose
a mechanism to show how this reaction goes with apparently complete retention of configuration, yet with
racemization. (Hint: Draw out the mechanism of the reaction of cyclopentene with Br2 in water to give the
starting material, trans-2- bromocyclopentanol. Consider how parts of this mechanism might be involved in the
reaction with HBr.)
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