See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Carbocation rearrangements (hydride shifts and alkyl/methyl shifts) occur when a more stable carbocation can be formed from a less stable one, or when ring expansion/contraction is possible. A carbocation will rearrange if there is a 1,2-hydride or 1,2-alkyl shift available that leads to a more stable (or equally stable but with relief of ring strain) carbocation. Step 1 - Structure (1): The carbocation is at an exocyclic tertiary carbon attached to cyclohexane with a methyl group. A 1,2-alkyl (ring carbon) shift can occur, migrating the ring C-C bond to give a ring-expanded carbocation (cycloheptyl-type tertiary carbocation). This rearrangement relieves strain or gives a more stable tertiary carbocation. So (1) will rearrange. Step 2 - Structure (2): The carbocation is on a secondary carbon in an open chain attached to a cyclohexane ring that bears two methyl groups (gem-dimethyl). A 1,2-hydride or methyl shift can convert this secondary carbocation to a tertiary carbocation. So (2) will rearrange. Step 3 - Structure (3): The carbocation is at a tertiary ring carbon (C1 of cyclohexane bearing a methyl group), with an ethyl group at C4. A 1,2-hydride shift within the ring can occur, and ring expansion is also possible. The carbocation can rearrange via hydride shift. So (3) will rearrange. Step 4 - Structure (4): The carbocation is at a carbon bearing two methyl groups and an ethyl group on the cyclohexane ring (tertiary carbocation). A 1,2-alkyl shift (ring expansion) can occur moving a ring carbon bond, giving a methylcycloheptyl-type cation or a more stable arrangement. So (4) will rearrange. Step 5 - Why not just (a), (b), or (d): Options (a), (b), and (d) exclude at least one structure that actually does rearrange. All four carbocations have viable pathways for rearrangement (ring expansion, 1,2-hydride, or 1,2-alkyl shifts), making 'All' the correct answer. Therefore, the correct answer is C.