Hydrogen Bonding and Entropy

A new general expression for the entropy S is given, based on the standard number 〈W〉 of “possibilities” of placing or moving for one molecule of a given kind. 〈W〉 is calculated in an independent way for all the different kinds of molecules present in the system

P. L. Huyskens; G. G. Siegel

2011

Scholarcy highlights

  • A new general expression for the entropy S is given, based on the standard number 〈W〉 of “possibilities” of placing or moving for one molecule of a given kind. 〈W〉 is calculated in an independent way for all the different kinds of molecules present in the system
  • The last term is related to the fact that in a liquid solution a given molecule has a larger volume at its disposal than its own one
  • During the fraction of time during which an hydroxyl proton is involved in H-bonding it renounces to the possibility of visiting its mobile domain, DomA, and remains confined in a small part V0 at the border of it
  • This creates in the liquid a kind of mobile order and a decrease of the entropy that is related to the ratio V0/〈DomA〉
  • The addition of an inert substance to the liquid increases 〈DomA〉, letting V0 inaltered. This corresponds to a decrease of the entropy that constitutes the true origin of the hydrophobic effect
  • The quantitative treatment leads to an equation that, without the use of any adjustable constant, correctly predict the solubility of liquid alkanes in water

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