In SN1 reactions, what dictates whether rearrangements occur?

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In SN1 reactions, what dictates whether rearrangements occur?

Carbocation stability is what governs rearrangements in SN1 reactions. After the leaving group departs to form a carbocation, the system will rearrange if a hydride or alkyl shift can produce a more stable cation. This is why secondary carbocations often rearrange to tertiary ones, or why allylic/benzylic positions may shift to more resonance-stabilized forms. If no rearrangement would increase stability, it typically won’t occur. While nucleophile strength and leaving group ability influence the rate of carbocation formation and capture, they don't determine whether rearrangements happen. Presence of nearby double bonds can provide resonance stabilization, but the driving force for rearrangement is the gain in carbocation stability through the shift.

Carbocation stability is what governs rearrangements in SN1 reactions. After the leaving group departs to form a carbocation, the system will rearrange if a hydride or alkyl shift can produce a more stable cation. This is why secondary carbocations often rearrange to tertiary ones, or why allylic/benzylic positions may shift to more resonance-stabilized forms. If no rearrangement would increase stability, it typically won’t occur. While nucleophile strength and leaving group ability influence the rate of carbocation formation and capture, they don't determine whether rearrangements happen. Presence of nearby double bonds can provide resonance stabilization, but the driving force for rearrangement is the gain in carbocation stability through the shift.

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