Consider the following carbocations and the correct stability order for the above carbocations is
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When assessing carbocation stability, always look for extended resonance/conjugation first, as this is the dominant factor, then evaluate the number of alpha-hydrogens for hyperconjugation.
Concept:
Carbocation stability is determined by electronic effects in the following order of significance: Resonance > Hyperconjugation > Inductive Effect.
Step 1: Analyze the structures.
Carbocations stabilized by resonance (conjugated systems like benzylic or allylic types) are significantly more stable than those stabilized only by hyperconjugation or inductive effects.
Step 2: Compare the effects.
Highly substituted carbocations that benefit from resonance stabilization are the most stable, followed by tertiary alkyl carbocations (hyperconjugation), then secondary, and finally primary alkyl carbocations.
Step 3: Conclusion.
Arranging the provided carbocations (a, b, c, d) based on these electronic effects leads to the stability sequence \((b) > (a) > (d) > (c)\).
