On the size, shape and energetics of the hydration shell around alkanes

Abstract

A large breath of clathrate-like cages has been proposed as the very first hydration shell of alkanes. The cages include canonical structures commonly found in clathrate hydrates and many others,...

Water model for hydrophobic cavities: structure and energy from quantum-chemical calculations

“…The values of Levy et al 38 are similar to the solvent reorganization enthalpy estimated as the difference between the experimental solution enthalpy and the computed encaging enthalpy (roughly 1, 2 and 4 kcal mol −1 for the 5 12 , 5 12 6 2 and 5 12 6 4 cages, respectively). 37…”

“…For instance, the optimal cage to host propane was predicted to be the smaller pentadecahedron, 5 12 6 3 , one. 37…”

“…The values of Levy et al 38 are similar to the solvent reorganization enthalpy estimated as the difference between the experimental solution enthalpy and the computed encaging enthalpy (roughly 1, 2 and 4 kcal mol À1 for the 5 12 , 5 12 6 2 and 5 12 6 4 cages, respectively). 37 Although the simplicity of the (H 2 O) 100 , (H 2 O) 120 and (H 2 O) 140 clusters are appealing in forming suitable shells for the 5 12 , 5 12 6 2 and 5 12 radii of B3.4 Å and B3.8 Å, respectively (Fig. 8).…”

“…In light of these ideas, a large number of clathrate-like structures have been recently proposed for the very first water shell around hydrocarbons and the side chain of aliphatic amino acids, obtaining a reasonable comparison with the available experimental and computational data. 36,37 Furthermore, the comparison of the calculated encapsulation enthalpies (cage–host interaction) and the experimental solution enthalpies obtained at 273.25 K is particularly intriguing. 37 At this temperature, the thermal motion is highly damped, and the water molecule configuration should not deviate much from the tangential orientation with respect to the solute surface.…”

“…36,37 Furthermore, the comparison of the calculated encapsulation enthalpies (cage–host interaction) and the experimental solution enthalpies obtained at 273.25 K is particularly intriguing. 37 At this temperature, the thermal motion is highly damped, and the water molecule configuration should not deviate much from the tangential orientation with respect to the solute surface. Qualitatively, the experimental and computational trends are similar although the latter are always more exothermic and the difference increases as the size of the solute increases.…”