Experiment Meets Theory: Cope Rearrangements and Thermal E/Z Isomerisations of Terpenoid Hydrocarbons

Several terpenes are known that can undergo a Cope rearrangement. Prominent examples include germacrene A and hedycaryol that show a Cope rearrangement already slightly above room temperature. In the present study the Cope rearrangements of several terpenes and eventually co‐occurring thermal E/Z isomerisations were investigated experimentally for their minimum required temperatures and for their states of equilibrium. The experimental findings were supported by computational assessments of free activation energies (ΔG‡) as well as relative Gibbs free energies of the reactants (ΔG).