Ab initio Gaussian calculations on the CH3 and CH2F cations

Abstract

Ab initio Hartree–Fock calculations with minimal basis sets of uncontracted Gaussian functions have been made for the planar and pyramidal conformations of CH₃⁺ and CH₂F⁺. Both cations are more stable in the planar form and the difference in energy between the equilibrium planar form and any pyramidal form was found to be greater for CH₂F⁺ than for CH₃⁺; single calculations with extended basis sets lead to the same result, which is in agreement with simple qualitative arguments and is consistent with experimental data. The C–H bond lengths in the two cations are about the same and the value for CH₃⁺ is in agreement with literature calculations in which extended basis sets were used. The optimum HCH angle in CH₂F⁺ is larger than 120°.