Alkene Reactions - II

For each of the reactions on the left, predict the major organic product. Pay particular attention to the regiochemistry of the reaction and the possibility of carbocation rearrangement.
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The addition of HOBr (formed from NBS in aqueous DMSO) to an alkene proceeds through an intermediate bromonium ion and results in the formation of a halohydrin with the hydroxide bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). Since a bromonium ion intermediate is involved, the overall stereochemistry is trans.

The addition of H⁺/H₂O to an alkene proceeds through a carbocation intermediate and results in the formation of an alcohol with the hydroxyl group bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). Rearrangements are commonly observed.

Oxymercuration of an alkene results in the formation of an alcohol with the hydroxyl group bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). The work-up with BH₄^- is necessary to reduce the organomercurial intermediate. Rearrangements do not occur.

The addition of HOBr (formed from NBS in aqueous DMSO) to an alkene proceeds through an intermediate bromonium ion and results in the formation of a halohydrin with the hydroxide bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). Since a bromonium ion intermediate is involved, the overall stereochemistry is trans.

The addition of HOBr (formed from NBS in aqueous DMSO) to an alkene proceeds through an intermediate bromonium ion and results in the formation of a halohydrin with the hydroxide bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). Since a bromonium ion intermediate is involved, the overall stereochemistry is trans.

The addition of H⁺/H₂O to an alkene proceeds through a carbocation intermediate and results in the formation of an alcohol with the hydroxyl group bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). Rearrangements are commonly observed.

Oxymercuration of an alkene results in the formation of an alcohol with the hydroxyl group bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). The work-up with BH₄^- is necessary to reduce the organomercurial intermediate. Rearrangements do not occur.

The addition of HOBr (formed from NBS in aqueous DMSO) to an alkene proceeds through an intermediate bromonium ion and results in the formation of a halohydrin with the hydroxide bonded to the alkene carbon which would form the most stable carbocation (Markovnikov addition). Since a bromonium ion intermediate is involved, the overall stereochemistry is trans.