Experimental and Theoretical Studies of the Vibrations and Structure of 2,2,2- trifluoroethyl trifluoroacetate, CF3CO2CH2CF3.

M. E. DEFONSI LESTARD; M. E.TUTTOLOMONDO; E. L. VARETTI; D. A. WANN; H. E. ROBERTSON; D. W. H. RANKIN; A. BEN ALTABEF

JOURNAL OF MOLECULAR STRUCTURE

Elsevier

Lugar: Amsterdam, Holanda; Año: 2009 vol. 917 p. 183 - 192

0022-2860

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 (HF, 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)CF3 bond, the anti, anti structure is preferred. This preference was studied using the total energy scheme and the natural bond orbital partition scheme. (Although an additional conformer exists by rotation about the C(=O)–O bond, it is so much higher in energy that it is ignored in this study.) Additionally, the total potential energy has been deconvoluted using a 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–