Conformational Properties and Gas-Phase Structure of (Fluorocarbonyl)sulphenyl Chloride, FC(O)SCl. Electron Diffraction, Vibrational Analysis and ab-Initio Calculations

CARLOS OMAR DELLA VEDOVA; MACK, H.; OBERHAMMER, HEINZ

JOURNAL OF PHYSICAL CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington; Año: 1991 vol. 95 p. 4238 - 4241

0022-3654

The gas-phase structure and conformational composition of FC(O)SCl were determined by electron diffraction. The following geometric parameters (ra distances and 〈α angles with 3σ uncertainties) were derived for the trans conformer: O=O = 1.179(4) Å, C-F = 1.342(4) Å, S-C = 1.756(5) Å, S-Cl = 1.996(3) Å, C-S-Cl = 100.3(5)°, S-C=O = 130.9(5)°, S-C-F = 105 3(3)° The free-energy differences ΔG° = G°(cis) - G°(trans) from the electron diffraction experiment (ΔG°(ED) = 1.2(3) kcal/mol) and from matrix IR spectra (ΔG°(IR) = 1.4(1) kcal/mol) are equal within their estimated error limits. Ab initio calculations at various levels of theory (HF, MP2, and MP4) reproduce the experiment very well (ΔE = 1.25-1.60 kcal/mol). Additional calculations for thioformic acid and various fluorine- and/or chlorine-substituted derivatives reveal a strong substituent effect on the conformational properties.