Abstract
This article is a review of recent progress in studies on the structure of liquid water and the influence of solutes on it.
Water is an extremely abnormal liquid consisting of monomer water and associated water bound by hydrogen bonding. The equilibrium of monomer and associated water is influenced by solutes, and study of the aqueous solutions leads to an understanding of water structure. Whereas ions with strong electric field enhance the water structure as a whole, those with weak electric field destroy the water structure. Hydrophobic solutes make another kind of water structure (icebergs) around them. The structure of the icebergs is different from that of ordinary ice and also of water under electric field of ions. The iceberg structure is supposed from the crystal structure of clathrate hydrates of symmetrical tetraalkylammonium salts. The behaviors of hydrophobic solutes in water and also the structure of associated water are explained from the viewpoint of the icebergs. Hydrophilic solutes affect the icebergs. Urea, a typical hydrophilic substance, breaks the water structure. Properties of aqueous solutions of alcohols, which have both hydrophilic and hydrophobic groups, are very complex.
