Hydrogen-bonding behaviour in the hydrophobic hydration of simple hydrocarbons in water

Abstract

The results of a series of molecular dynamics simulations of aqueous solutions of methane and ethane and of pure water are reported. The results imply a larger fraction of broken hydrogen bonds in the hydration shell of non-polar solutes with respect to bulk water, the difference increasing with rise of temperature. Evidence is found of stronger hydrogen bonds in the hydration shell. The results can be related to Muller's modified hydration-shell hydrogen-bond model of hydrophobic hydration, based on the notion of hydrogen bonds in the hydration shell of non-polar solutes having smaller bond-breaking Gibbs energies. This picture of hydrogen-bonding is reinterpreted in the light of recent themodynamic models of hydrophobic hydration.