Experimental and theoretical studies of the vibrations and structure of 2,2,2-trifluoroethyl trifluoroacetate, CF3CO2CH2CF3

Maria Eliana Defonsi Lestard, Maria Eugenia Tuttolomondo, Eduardo Lelio Varetti, Derek A. Wann, Heather E. Robertson, David W. H. Rankin, Aida Ben Altabef

Research output: Contribution to journalArticlepeer-review

Abstract

The molecular structure of 2,2,2-trifluoroethyl trifluoroacetate, CF3CO2CH2CF3, has been determined in the gas-phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using basis sets up to 6-311++G(d,p). Both experimental and theoretical data indicate that although both structures with anti, anti (Cs) and anti, gauche (C1) conformations exist by rotating about the O-C(H2) bond, the anti, anti structure is preferred. The difference in free energy was calculated to be 2.1 kJ mol-1 (Cs conformer lower in energy) and as the C1 conformer has a double multiplicity relative to the Cs conformer, the ratio of C1:Cs conformer was predicted to be 0.41:0.59.
This conformational preference was studied using the total energy scheme and the natural bond orbital partition scheme. Additionally, the total potential energy has been deconvoluted using six-fold decomposition in terms of a Fourier-type expansion. Infrared spectra of CF3CO2CH2CF3 have been obtained for the gaseous, liquid and solid phases and the Raman spectrum for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root-mean-square deviation of 7.3 cm-1.

Original languageEnglish
Pages (from-to)183-192
Number of pages10
JournalJournal of Molecular Structure
Volume917
Issue number2-3
DOIs
Publication statusPublished - Jan 2009

Keywords

  • 2,2,2-Trifluoroethyl trifluoroacetate
  • Gas-phase electron diffraction
  • Ab initio calculations
  • DFT calculations
  • Internal barrier to rotation
  • Infrared and Raman spectroscopy
  • PHASE ELECTRON-DIFFRACTION
  • MOLECULAR-ORBITAL THEORY
  • GAS-PHASE
  • AB-INITIO
  • EQUILIBRIUM STRUCTURES
  • CRYSTALLINE PHASES
  • INTERNAL-ROTATION
  • ORGANIC-COMPOUNDS
  • TRIFLUOROMETHANESULFONATE
  • APPROXIMATION

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