Hydrophobic effects in the water network structure of aqueous solutions of a semiclathrate molecule

In-phase collective small amplitude proton motions are observed in the OH stretching Raman spectrum of the semiclathrate crystalline hydrate of tetra-n-butyl ammonium hydroxide, its melt and aqueous solutions. These are quantified and used in dilute solutions as a probe of the network structure of water surrounding the molecule. Clear evidence of structural enhancement of the network is obtained in dilute solutions as well as the destruction of the network by hydrophobic interactions as the concentration is increased. Evidence for change of molecular conformation, suggesting intramolecular hydrophobic interactions, is obtained from the CH stretching spectra.