Case study of enthalpy-entropy noncompensation.
Enthalpy-entropy noncompensation characterizes the relative changes in the hydration thermodynamic functions upon "transforming" ethane into fluoromethane, chloromethane, bromomethane, and iodomethane. An analysis grounded on a simple statistical mechanical theory of hydration allows a plausible rationalization of such enthalpy-entropy noncompensation. It is shown that increasing the strength of solute-water attractive interactions modifying the chemical nature of a part of the solute molecule, but not its size, is a largely noncompensating process for the hydration of noncharged and nonhydrogen bonding species, and dominates the compensating contribution coming from the reorganization of water H bonds.
Graziano
Giuseppe
G
Dipartimento di Scienze Biologiche ed Ambientali, Universita del Sannio, Via Port'Arsa, 11-82100 Benevento, Italy. graziano@unisannio.it
D003198:Computer Simulation; D004735:Energy Transfer; D019277:Entropy; D004980:Ethane / Q000737:chemistry*; D008697:Methane / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D014867:Water; D004980:Ethane; D008697:Methane