Fluctuations in aqueous solutions of some hydrophobic solutes

The entropy fluctuation in liquids and solutions is most conveniently normalzied to the coarse-grained volume. Hence,〈(ΔS/V)2〉 = RCp/Vm2 and〈ΔS/V)(ΔN/N)〉 = RTαp/Vm. It is shown to be useful if the response functions,Cp,χT andαp, and the fluctuations derived from them, were discussed separately in contrasting the peculiar nature of liquid H2O against a typical van der Waals liquid, benzene. The composition dependence of these fluctuations was examined in aqueous solutions of typical hydrophobic solutes, 2-butoxyethanol, 2-butanone and tert-butanol. It was concluded that the above solutes reduce the hydrogen bond probability in H2O up to the crossover point of mixing scheme,xic.