Most condensation reactions are reversible. The prefix retro, which means "backward," is frequently used to describe the opposite reaction. Below is a plausible mechanism for the reaction of 1-(2-hydroxy-4-methylcyclobutyl)ethanone to 3,5-dimethylcyclohex-2-enone. Identify what steps in the mechanism are involved in the migration of a double bond to form an enol isomer.