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Carbonium ion rearrangement results in a more stable carbonium ion and probably happens in the actual formation of the carbonium ion not in a time delayed subsequent reaction. If this is the case there is little sense in first looking at the migrating moiety but to first look for the most stable carbonium ion then second to look for the better migrating ...


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This is essentially a question of thermodynamic control versus kinetic control. The statement "my teacher told me that Hydrogen is the best migrator" has to do with the migration barrier, which is related to kinetic control. Since H atom is very light, its vibrational frequency can be high, which may facilitate the migration. Being a light atom, ...


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Your question is an example of Cationic Rearrangements. When a reaction is set to progress under correct condition for thermodynamic control, the final product is based on the thermodynamic stability of intermediates. The migratory aptitude matters if the intermediate stability increased by the migration (see the examples given in here). For instance, in $\...


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Yours textbook answer is correct. We can't just say that hydrogen is a best migrator. Shifting of groups depends on the stability of transition state and final product. In this example, you can observe that carbocation in C is a tertiary carbon with 6 hyperconjugative structures whereas in D carbocation is a secondary carbon with only 4 hyperconjugative ...


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