Because there is σ-donation between the σC−H bonds and the π∗C−C, partially populating this orbital will shift electron density to the right (think of it as partially breaking the...Because there is σ-donation between the σC−H bonds and the π∗C−C, partially populating this orbital will shift electron density to the right (think of it as partially breaking the πC−C bond, with electrons continuing to move along the chain). Thus, the second key difference in the reaction coordinate diagram is that the height of the first transition state is much greater for the formation of the 1 o carbocation.
