Here, ∆𝐺 quantifies the free energy difference caused by the disruption of hydrogen bonding interactions among H 2 O and solvent molecules as these species reorganize to accommodate the formation of the reactive intermediate that precedes the epoxidation transition state, which strongly resembles the transition state itself. . The dashed lines represent the values of ΔH HB and ΔS HB measured via variable temperature IR spectroscopy in the bulk fluid phase (black) or in Ti-FAU (orange), Ti-BEA (blue), and Ti-MFI (purple). The upper line for each of the Ti-zeolites corresponds to the most hydrophilic material, while the lower linear corresponds to the most hydrophobic sample. The shaded region is intended to represent the span of enthalpy -entropy compensation expected within these different pore environments due to the differences in (SiOH) x for a given zeolite topology.