This work also includes a configurational entropic contribution from the external medium. The effective potential energy profile for a reaction at a given pressure 𝑝 is then determined by computing 𝐺 232 (𝑝) for a set of selected structures along a suitable reaction coordinate. According the transition state theory, the activation volume ∆𝑉 ‡ is determined from the slope of the corresponding activation energy ∆𝐺 232 ‡ (𝑝) as a function of the pressure, In this work, the effective potential energy profile for a reaction at a given pressure 𝑝 is then determined by computing 𝐺 232 (𝑝). The corresponding activation volume ∆𝑉 ‡ is computed by the same computational protocol used previously for the study of the effect of pressure on a selection of pericyclic reactions, where reasonable agreement of the computed activation volumes with experiment values was obtained. We recommend that interested readers consult ref 17 and the SI of the current paper for a detailed tutorial about the protocol. All the XP-PCM calculations are performed for selected structures (reactants, transition state, product) along the gas phase intrinsic reaction coordinates.