Transformational model general separation structure

The most widely used qualitative model for the explanation of the shapes of molecules is the Valence Shell Electron Pair Repulsion (VSEPR) model of Gillespie and Nyholm (25). The orbital correlation diagrams of Walsh (26) are also used for simple systems for which the qualitative form of the MOs may be deduced from symmetry considerations. Attempts have been made to prove that these two approaches are equivalent (27). But this is impossible since Walsh s Rules refer explicitly to (and only have meaning within) the MO model while the VSEPR method does not refer to (is not confined by) any explicitly-stated model of molecular electronic structure. Thus, any proof that the two approaches are equivalent can only prove, at best, that the two are equivalent at the MO level i.e. that Walsh s Rules are contained in the VSEPR model. Of course, the transformation to localised orbitals of an MO determinant provides a convenient picture of VSEPR rules but the VSEPR method itself depends not on the independent-particle model but on the possibility of separating the total electronic structure of a molecule into more or less autonomous electron pairs which interact as separate entities (28). The localised MO description is merely the simplest such separation the general case is our Eq. (6)... 

Within an environmental compartment physical and chemical transformations ol specified chemical compounds such as pollutants or probe compounds or any other chemical species P, are generally controlled both by different environmental factors Ej, such as the activities of environmental reactants acting on them ( driving force ), and the compound-specific rate constant, kJ P, with which the specific chemical structures of P respond to such factors j (Smith et al., l t /7). Only a strict separation between the terms corresponding to environmental parameters and the chemical constants describing the chemical compound allows for easy generalization of the rate laws and for structuring of kinetic environmental models ... 

---