Gas-phase structure and new vibrational study of methyl trifluoroacetate (CF3C(O)OCH3)

Maria E. Defonsi Lestard, Maria E. Tuttolomondo, Eduardo L. 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 methyl trifluoroacetate (CF3C(O)OCH3) has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using different basis sets. Experimental data revealed an anti conformation with a dihedral angle θ(CCOC) = 180 degrees. Quantum mechanical calculations indicate the possible existence of two conformers, differing by a rotation about the C(O)-O bond. The global minimum represents a Cs-symmetric structure in which the CF3 group has the anti orientation with respect to the CH3 group, but there is another potential minimum, much higher in energy, representing a Cs-symmetric structure with a cis conformation. The preference for the anti conformation was studied using the total energy scheme and the natural bond orbital (NBO) partition scheme. Additionally, the total potential energy has been deconvoluted using a six-fold decomposition in terms of a Fourier-type expansion, showing that the electrostatic and steric contributions are dominant in stabilizing the anti conformer. Infrared spectra of CF3C(O)OCH3 were obtained for the gaseous and liquid phases, while the Raman spectrum was recorded for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root mean-square deviation of 9 cm-1 when comparing experimental and calculated frequencies.

Original languageEnglish
Pages (from-to)2053-2062
Number of pages10
JournalJournal of Raman Spectroscopy
Volume40
Issue number12
DOIs
Publication statusPublished - Dec 2009

Keywords

  • methyl trifluoroacetate
  • gas electron diffraction
  • ab initio calculations
  • DFT calculations
  • infrared spectra
  • Raman spectra
  • MOLECULAR-ORBITAL THEORY
  • ELECTRONIC-STRUCTURE
  • INTERNAL-ROTATION
  • ORGANIC-COMPOUNDS
  • INFRARED-SPECTRA
  • AB-INITIO
  • FORMALDEHYDE
  • ETHYLENE

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