PUB - Publikationen an der Universität Bielefeld

The simple 2,2,2-trifluoroethyl thionitrite molecule, CF3CH2SNO, has been prepared in good yield for the first time using CF3CH2SH and NOCl in slight excess. The vapor pressure of the red-brown compound CF3CH2SNO follows, in the temperature range between 226 and 268 K, the equation log p = 12.0-3881/T (p/bar, T/K), and its extrapolated boiling point reaches 51 degrees C. Its structural and conformational properties have been compared with the ethyl thionitrite analogue, CH3CH2SNO. The FTIR spectra of the vapor of both thionitrites show the presence of bands with well-defined contours, allowing for a detailed conformational analysis and vibrational assignment on the basis of a normal coordinate analysis. The conformational space of both thionitrite derivatives has also been studied by using the DFT and MP2(full) level of theory with extended basis sets [6-311+G(2df) and cc-pVTZ]. The overall evaluation of the experimental and theoretical results suggests the existence of a mixture of two conformers at room temperature. The relative abundance of the most stable syn form (N=O double bond syn with respect to the C-S single bond) has been estimated to be ca. 79 and 75% for CF3CH2SNO and CH3CH2SNO, respectively.