Figure shows values of values of ΔH excess increase linearly with ΔS excess for 1-alkene epoxidations within Ti-FAU, Ti-BEA, and Ti-MFI catalysts, which reflects enthalpy-entropy (H-S) compensation effects widely reported for catalytic reactions and intimately tied to the dynamic restructuring of HB networks of H 2 O molecules within the zeolite pores (Fig. , Table ). The values of ΔH excess and ΔS excess increase in proportion to one another with increasing 1-alkene chain length, which suggests that the perturbation of H 2 O molecules, and consequently values of ΔH excess and ΔS excess , increase with the number of methylene units of the reactants. Within Ti-FAU, values of ΔG excess (at 313 K, via ΔG excess = ΔH excess + TΔS excess ) lie near 0 kJ mol -1 , which agrees with rate ratios for 1-alkene epoxidation over Ti-FAU-OH and Ti-FAU-F that do not depend on alkene chain length (Fig. ). In contrast, values of ΔG excess become increasingly negative with chain length or (SiOH) x density within Ti-BEA zeolites, because the entropy gain associated with disrupting H 2 O clusters confined within BEA pores overwhelms the enthalpic cost of reorganizing these molecules. These comparisons reveal the molecular origins for epoxidation rate ratios that increase with 1-alkene chain length in Ti-BEA-OH and Ti-BEA-F (Fig. ). The same phenomenon appears also within Ti-MFI materials only to a larger extent with rate ratios between Ti-MFI-OH to Ti-MFI-F that reach a factor of 400 for 1-decene epoxidation (Fig. ). These greater gains in ΔS excess for epoxidation transition states in Ti-MFI reflect the low value for <N HB >, in comparison to other zeolite frameworks, which give rise to larger entropy gains by liberating H 2 O molecules for the minimal enthalpic cost (Table ).