%0 Journal Article
%A Kuze, Nobuhiko
%A Ishikawa, Atsushi
%A Kono, Maho
%A Kobayashi, Takayuki
%A Fuchisawa, Noriyuki
%A Tsuji, Takemasa
%A Takeuchi, Hiroshi
%D 2015
%T Molecular
Structure and Internal Rotation of CF3 Group of Methyl
Trifluoroacetate: Gas Electron Diffraction,
Microwave Spectroscopy, and Quantum Chemical Calculation Studies
%U https://acs.figshare.com/articles/journal_contribution/Molecular_Structure_and_Internal_Rotation_of_CF_sub_3_sub_Group_of_Methyl_Trifluoroacetate_Gas_Electron_Diffraction_Microwave_Spectroscopy_and_Quantum_Chemical_Calculation_Studies/2189977
%R 10.1021/jp508447b.s001
%2 https://ndownloader.figshare.com/files/3824143
%K Quantum Chemical Calculation StudiesThe
%K JK
%K quantum chemical calculations
%K CCOC
%K methyl trifluoroacetate
%K CF 3COOCH
%K conformer
%K CF 3 Group
%K MW data
%K OCO
%K GED
%K Gas Electron Diffraction
%K CCF
%K MHz
%K COC
%K V 3
%K CF 3 group
%K OCCF
%K gas electron diffraction
%K CH 3 groups
%K QC
%X The molecular structure of methyl
trifluoroacetate (CF3COOCH3) has been determined
by gas electron diffraction
(GED), microwave spectroscopy (MW), and quantum chemical calculations
(QC). QC study provides the optimized geometries and force constants
of the molecule. They were used to estimate the structural model for
GED study and to calculate the vibrational corrections for GED and
MW data. In addition, potential energy curves for the internal rotations
of CF3 and CH3 groups have been calculated for anti (dihedral angle of α(CCOC) is 180°) and syn (α(CCOC) = 0°) conformers of methyl trifluoroacetate.
Both the GED and MW data revealed the existence of the anti conformer. Molecular constants determined by MW are A0 = 3613.4(3) MHz, B0 = 1521.146(8)
MHz, C0 = 1332.264(9) MHz, ΔJ = 0.09(2) kHz, and ΔJK = 0.23(6) kHz. The
GED data were well-reproduced by the analysis in which a large-amplitude
motion of the CF3 group was taken into account. The barrier
of the internal rotation of the CF3 group was determined
to be V3 = 2.3(4) kJ mol–1, where V3 is the potential coefficient
of the assumed potential function, V(ϕ) = (V3/2)(1 – cos 3ϕ), and ϕ
is a rotational angle for the CF3 group. The values of
geometrical parameters (re structure)
of the anti conformer of CF3COOCH3 are r((O)C–O) = 1.326(6)
Å, r(O–CH3) = 1.421(4) Å, r(C–Hin‑plane) = 1.083(14) Å, r(C–Hout‑of‑plane) = 1.087(14)
Å, r(CO) = 1.190(7) Å, r(C–C) = 1.533(4) Å, r(C–Fin‑plane) = 1.319(4) Å, r(C–Fout‑of‑plane) = 1.320(6) Å, ∠COC
= 116.3(5)°, ∠OCHin‑plane = 105.2°
(fixed), ∠OCHout‑of‑plane = 110.0°
(fixed), ∠OCC = 123.7° (fixed), ∠O–CC
= 111.2(5)°, ∠OCO = 125.2(5)°, ∠CCF = 110.1(3)°,
and OCCF (out-of-plane dihedral angles) = ± 121.5(1)°. Numbers
in parentheses are three times the standard deviations of the data
fit.
%I ACS Publications