Conformational Properties of Ethyl- and 2,2,2-Trifluoroethyl Thionitrites, (CX3CH2SNO, X = H and F)

ANTONELA CANNEVA; CARLOS OMAR DELLA VEDOVA; NORBERT MITZEL; MAURICIO ERBEN

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014

1089-5639

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 °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.