Question

In which of the following reactions of alkenes can carbocation rearrangements occur?

• A. The addiion of $B{r}_2$ and $H_{2}O$ to a $C=C$ (halohydrogenation)
• B. The addition to $C{l}_2$
• C. The addition of $H_{2}O$ in presence of acid
• D. Both A and C

Answer 1

The correct option is C The addition of $H_{2}O$ in presence of acid

The acid catalyzed hydration of alkene takes place as electrophilic addition reaction. The reaction involves the formation of carbocation intermediate. In reactions involving carbocation intermediates, the carbocation may sometimes rearrange if a more stable carbocation can be formed by the rearrangement. These involve hydride and methyl shifts.

The addition of $C{l}_2$ or $B{r}_2$ and $H_{2}O$ involves halonium ion intermediate which can not undergo rearrangement.