# Acid catalysed dehydration of alcohol with a bicyclo group

Pathway 1: Rate determining step is the formation of carbocation. In this pathway, a conjugated tertiary carbocation is generated as an intermediate.

Pathway 2: One of the resonance form of intermediate carbocation proceeds to produce a more stable product (due to benzene ring) through alkyl migration. Though, the resonating form of carbocation is conjugated secondary carbocation which is less stable than the carbocation formed through pathway 1.

My questions are:

1- Is tert-butyl (don't know the correct term) migration possible in pathway- 2?

2- What are the major and minor products? Which factor will decide the major product: stability of final compound or the most stable intermediate?

• The reactant/intermediate is clearly not aromatic, but the product is. What about the $\ce{\Delta H, \Delta G}$ of reaction? Aug 8, 2020 at 10:40
• This reaction is under thermodynamic control. All of steps are reversible but the last step to form aromatic compound. Hence, aromatic compound is the major. The product from first path is still susceptible to protonate under acidic conditions. Aug 8, 2020 at 16:26
• " resonating form of carbocation is conjugated secondary carbocation which is less stable than the carbocation formed through pathway 1" - that's wrong on many levels. Aug 8, 2020 at 21:38
• I have never seen a migration of a t-butyl group before. That seems sterically problematic.
– Zhe
Aug 8, 2020 at 22:08
• @Zhe Migratory aptitude might depend on the reaction. According to wikipedia for pinacol rearrangement the order is Hydride > $\ce{(CH3)3}$> Phenide > $\ce{C2H5}$ > $\ce{CH3}$ and per this site for Baeyer-Villiger rearrangement the order is 3º-alkyl > 2º-alkyl ~ benzyl ~ phenyl > 1º-alkyl > methyl (depends on electron density). Aug 9, 2020 at 6:24