Consider the reaction of 2,8-dimethylnon-7-en-2-ol with catalytic H ^+ and heat, followed by the addition of HBr . The major product of this reaction is:

Step-by-step solution

Protonation of the hydroxyl group of 2,8-dimethylnon-7-en-2-ol followed by the loss of a water molecule generates a stable tertiary carbocation at C2. Intramolecular electrophilic addition then occurs. The C7=C8 pi bond attacks the C2 carbocation. Attack by C7 forms a relatively strain-free 6-membered ring (cyclohexane derivative) and leaves a stable tertiary carbocation at the exocyclic C8 position. Attack by C8 is disfavored as it would form a strained 7-membered ring with a less stable secondary carbocation at C