In carbocation rearrangements, alkyl shifts typically occur when the adjacent carbon is tertiary, as this allows for the formation of a more stable carbocation. Hydride shifts are not possible from tertiary carbons due to the absence of hydrogen atoms. The discussion emphasizes the importance of evaluating the stability of the carbocation formed after potential shifts. If an alkyl shift can yield a more stable tertiary carbocation from a secondary one, it should be prioritized. If neither alkyl nor hydride shifts are feasible, the original carbocation should be retained. The effectiveness of this approach is noted to be applicable in most cases, although specific examples of simultaneous hydride and alkyl shifts leading to the same carbocation are not readily identified.
