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Unformatted text preview: WHY this reversal in regioselectivity is observed. Note if you replace the benzene with a cyclohexane, only the usual Markovnikov addition product is observed. + H-Br As always, the H-Br can add two ways to this alkene. One would normally expect the reaction to proceed via the 3 o carbocation, but it turns out that this is not the favored pathway here. Despite being a 2 o carbocation, the first is a more stable carbocation, due to resonance delocalization of the positive charge throughout the benzene ring. The 3 o carbocation has no additional stability, so the top pathway turns out to be the energetically favored one. favored pathway + H-Br Br Major product Br Only trace amounts formed +...
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