Abstract: Pinacol rearrangement is an important topic in undergraduate organic chemistry courses, but students often struggle to fully understand and grasp the rearrangement mechanism, regioselectivity and group migration aptitude. In order to enhance students’ comprehension of pinacol rearrangement reactions, we design an experiment that utilizes computational chemistry methods to address organic chemistry problems. Through intuitive visuals and specific data, the experiment clearly demonstrates that substrates capable of forming stable carbocation intermediates primarily undergo stepwise rearrangement mechanisms, while those unable to form stable intermediates undergo concerted rearrangement mechanisms. The computational results validate that the regioselectivity of the reaction depends on the protonation site of the neighboring diol hydroxyl group and the group migration ability, and it unequivocally establishes the order of group migration ability as hydrogen > aromatic > alkyl. Furthermore, a rational explanation for this order is provided from a microscopic perspective.

Key words: Pinacol rearrangement, Reaction mechanism, Migratory aptitude, DFT calculations