Coulomb interaction covalent binding

To incorporate these qualitative ideas into a quantitative account of covalent binding the Heitler-London (HL) prescription is most effective. It must be formulated in terms of two monopositive cores at coordinates and X, and two electrons of which the coordinates are represented by ri and r2. The Coulombic interaction between these particles is expressed as... 

In sohds, then, the forces which tend to impose order on the individual chemical units may be van der WaaJs forces, as with the inert gases, with elements which form diatomic molecules, and with organic substances they may be Coulomb forces between ions, as in many simple salts and with the positive ion-electron interaction in metals and, finally, they may be the covalencies binding atom to atom throughout extended regions of space. 

Donor-acceptor effects, covalent contributions, and Pauli repulsion and dispersion interactions all require that both binding partners have associated electron density. This presents us with the opportunity to isolate purely electrostatic effects (Coulomb interactions and polarization) by using simple electrostatic models for one of the partners. Some care must be exercised when using this technique because large (and especially diffuse) basis sets on one partner have significant values in the... 

The problem of binding purely covalent substrates is expectedly difficult because of the lack of centers capable of providing a strong electrostatic attraction. For these compounds it is necessary to elaborate receptors able to bind substrates effectively via van der Waals interactions, which are much weaker than the Coulomb forces operating in the previously mentioned complexes. A set of models designed for this purpose is shown in Scheme 4.68. Cyclophanes of the general formula 226 have been synthesized as hosts for aromatic hydrocarbons. The presence of a hydrophobic cavity of... 

A Lewis structure of a H-bond violates the octet principle of striving toward two electrons around each hydrogen. Much weaker than a conventional covalent bond, the H-bond is stronger than the van der Waals forces that bind together nonpolar molecules. While Coulombic attraction between polar molecules certainly contributes toward the interactive force, the H-bond is nonetheless considered to be more than a simple electrostatic interaction. 

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