In carbocation stability, which carbocation forms the major product?

• A. Primary carbocation
• B. Secondary carbocation
• C. Tertiary carbocation
• D. No carbocation forms

Answer: (C)

Carbocation stability is the key driver of which path dominates. The more substituted a carbocation is, the more stable it becomes: tertiary carbocations are stabilized by three adjacent alkyl groups that donate electron density through hyperconjugation and inductive effects, more than secondary (two groups) or primary (one group). Because a reaction that goes through a carbocation intermediate tends to favor the most stable intermediate, the route that forms a tertiary carbocation is favored, making the product derived from that intermediate the major one. The primary and secondary options are less stabilized and thus contribute less to the major outcome. The idea that no carbocation forms would apply only to mechanisms that proceed without a cation, but for carbocation-driven pathways, the tertiary route dominates.