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Gas‐phase structure and new vibrational study of methyl trifluoroacetate (CF 3 C(O)OCH 3 )
Author(s) -
Defonsi Lestard María E.,
Tuttolomondo María E.,
Varetti Eduardo L.,
Wann Derek A.,
Robertson Heather E.,
Rankin David W. H.,
Ben Altabef Aida
Publication year - 2009
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2371
Subject(s) - chemistry , dihedral angle , conformational isomerism , natural bond orbital , raman spectroscopy , crystallography , ab initio , steric effects , ab initio quantum chemistry methods , bond length , molecular geometry , methyl group , potential energy , computational chemistry , density functional theory , crystal structure , stereochemistry , group (periodic table) , hydrogen bond , molecule , atomic physics , physics , optics , organic chemistry
The molecular structure of methyl trifluoroacetate (CF 3 C(O)OCH 3 ) 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°. 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 C s ‐symmetric structure in which the CF 3 group has the anti orientation with respect to the CH 3 group, but there is another potential minimum, much higher in energy, representing a C s ‐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 CF 3 C(O)OCH 3 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. Copyright © 2009 John Wiley & Sons, Ltd.