About environmental isomers and their existence in liquid water

Environmental isomers in a liquid are molecules of a single species that become distinguishable because they exist in distinct solvent cages. Concepts involved in environmental isomerism are defined and criteria for distinguishability derived, first by neglecting Brownian potential energy noise, then by including it. Two models are used in the simulations of a molecule jumping from a cage of one type to another. (i) On every Brownian "collision," the associated Schroedinger state wave is continuous, i.e., collisions and transits between cages are accompanied by zero phase change. (ii) On every collision and transit, there is a random phase change in the state wave. The properties of liquid water are reviewed in terms of a two-state model in which the states are environmental isomers. It is shown that (i) the difference in enthalpy and entropy between the isomers, (ii) the positions and width of their IR stretching frequencies, as well as (iii) dielectric constant, ( iv) molar volume, and (v) O···O radial distribution data are in agreement with a model in which the more stable isomer is H2O\4w (a water molecule in a cage of four water molecules) and the less stable isomer is H2O\5w. The widths of the IR bands indicate that the water-water interactions are through "linkage pairs" in which the motions of the individual molecules comprising a cage are essentially independent.