Electrostatic forces and geometry of organic molecules. Part I. Saturated molecules with tetrahedral fragments

A new qualitative approach for analysis of organic molecules geometry, which can be considered as a development of known VSEPR concept is suggested. The core of the approach is electrostatic model, based on the division of the total electron density into an isotropic component which after summation with the nuclear charges turn them into point positive charges (PPCs), and an anisotropic component, tied to the local electron densities (LEDs) of chemical bonds and lone pairs of electrons (LPs). Electrostatic forces (ESFs) affecting the LEDs and PPCs in typical tetrahedral molecular fragments with central carbon atom or heteroatom are considered in detail. The procedure of conditional fixation of PPCs followed by evaluation of perturbing electrostatic forces arising in passing from a particular molecule, or molecular conformation, to another one is applied. Using the existing experimental and ab initio calculation data the model capabilities are demonstrated for typical organic molecules consisting of Н, С, N, O, F, Si, S and Cl atoms.