Steric and Electronic Structure of C6H5XCF3 Molecules (X = O or S): A Quantum-Chemical Study

Abstract

The potential functions of internal rotation around the Csp2-X bond in C6H5XCF3 molecules (X = O or S) were obtained by quantum-chemical calculations in the HF/6-31G(d), MP2(f)/6-31G(d), and B3LYP/6-31G(d) approximations. The calculations were performed in the range of torsion angles φ (angle between the planes of the benzene ring and Csp2-X-Csp3 bonds) from 0° to 90° with a 15° step. The barriers to rotation around the Csp2-X bonds (kJ mol-1) were evaluated: for C6H5XCF3, 7.60 (HF), 3.04 (MP2), and 1.04 (B3LYP); for C6H5XCF3, 16.57 (HF), 14.67 (MP2), and 8.73 (B3LYP). The geometries (bond angles and bond lengths), Koopmans ionization potentials, and dipole moments of the molecules were calculated. The hybridization, energy, and population of the lone electron pairs of the heteroatoms, and also the energy of their resonance interaction with antibonding orbitals and the natural atomic charges were evaluated using the NBO approach.