A quantum mechanical localized molecular orbital study of the physical process of the planar (D3h) to pyramidal (C3v) structural reorganization of trifluoro methyl cation

An important carbocation, CF3+ occurs in planar (D-3h) structure but quickly reorganizes to pyramidal (C-3v) form in chemical response prior to the event of chemical reaction. The structural reorganization process is associated with a significant stretching of C-F bond and redistribution of charge density, A quantum mechanical study of the physical process of structural evolution of CF3+ system is carried out invoking the localization technique of Sinanoglu and energy partitioning analysis of Kollmar and Fischer. Quantum mechanical hybridizations in the molecule, and the energy of the 'C-F' bond are evaluated in a number of generated conformations of the chemical species. A number of diverse parameters that can correlate the energetic, kinetic and structural aspects of the ionic species are also evaluated as a function of structural deformation. The computed quantities are found to be important inputs in explaining the energetic and binding aspects of the evolution of molecular shape, and in correlating the chemical reactivity of the CF3+ system. A rationale of the pattern of charge rearrangement in the ionic species is put forward in terms of the dynamic variation of electronegativity with the evolution of conformations. Results demonstrate that the variation of the strength of the C-F bond and the percentage of s-character of the hybrids of 'C' and 'F' atoms forming the bond as a function of D-3h to C-3v structural evolution are in accordance with suggestions of Brown and Coulson in this regard.