Hartree-Fock and post-Hartree-Fock studies on cis-trans equilibrium of fluoroformyl hypofluorite FC(O)OF: reliability of predicted thermodynamic properties and molecular structures

摘要

A Hartree-Fock and post-Hartree-Fock study on the cis-trans equilibrium of fluoroformyl hypofluorite, FC(O)OF, is presented. Pople's split-valence double- and triple-zeta quality basis sets, augmented with sets of polarization and diffuse functions (6-31G(d), 6-311G(d), 6-311G(2df) and 6-311 +G(2df)), correlation consistent polarized valence triple-zeta Dunning's (aug-cc-pVTZ), and medium-size polarized Sadlej's (MSPBS) basis sets were used at the HF and at the MP2, MP4(SDQ), MP4(SDTQ), CCSD, CCSD(T), and DFT correlated levels. For all applied methods, trans-FC(O)OF is predicted to be more stable than the cis isomeric form, in agreement with experimental data. ΔE(cis = > trans) values range from -1.70 (CCSD/6-311G(d)) to -0.16 kcal mol~(-1) (DFT/6-311 G(d)) and the cis-trans barrier height ranges from 9.60 (MP2/6-311 G(2df)) to 8.56 kcal mol~(-1) (MP4(SDQ)/6-311+G(2df)). Reliable geometries and IR harmonic vibrational frequencies were obtained using the DFT model with the Becke-Lee-Yang-Parr exchange-correlation potential.