Final answer:
Carbocation rearrangements do not occur in hydroboration-oxidation reactions because these reactions do not involve carbocation intermediates.
Step-by-step explanation:
The student's question asks whether carbocation rearrangements occur during hydroboration-oxidation reactions. In hydroboration-oxidation reactions, carbocations are not formed as intermediates; therefore, carbocation rearrangements do not occur. Instead, the hydroboration step involves the concerted addition of a boron hydride across the double bond in alkenes to form trialkylboranes, without the formation of any charged intermediates.
The oxidation step that follows converts these trialkylboranes into alcohols through a mechanism which involves concerted migration of the alkyl group and insertion of an oxygen atom, without any carbocation intermediate. As such, the issue of carbocation rearrangement does not arise in hydroboration-oxidation processes, contrasting with reactions such as tertiary alkyl halides substitutions, where such rearrangements are common. It's worth noting that hydroboration-oxidation provides anti-Markovnikov addition of water across the double bond, typically resulting in the formation of alcohols with high regio- and stereoselectivity.