Fundamentals of Organic ChemistryChemistryGeneral Organic Chemistry
Consider the following two carbocations: I II Which of the following statements correctly compares their stabilities?
Options
- AI is more stable than II
- BII is more stable than I
- CStability criterion cannot be applied in this case
- DBoth I and II are equally stable
Correct answer
B. II is more stable than I
Step-by-step solution
The stability of the given carbocations is primarily determined by hyperconjugation, which dominates over the inductive effect. The C-H bond is weaker than the C-D bond. As a result, the electrons in the C-H bond can more easily delocalize into the empty p-orbital of the positively charged carbon atom. Therefore, the -CH₃ group exhibits a stronger hyperconjugative effect compared to the -CD₃ group. This stronger hyperconjugation makes carbocation II more stable than carbocation I.