VIBRATIONAL-SPECTRA AND CONFORMATIONAL BEHAVIOR OF CARBONYL ISOTHIOCYANATES X-CO-NCS, X=F, CL, BR, MEO, ETO, AND ACETYL ISOTHIOCYANATE CH3-CO-NCS

Vibrational data for five carbonyl isothiocyanates X-CO-NCS, with X=F, Cl, Br, MeO and EtO, and for acetyl isothiocyanate CH3-CO-NCS are rep orted. Detailed assignments for the infrared and Raman data of the -F, -Cl and -CH3 species are given. The vapour phase IR spectrum of acetyl isothiocyanate suggests the presence of the cisoid conformer only but the spectra of all the carbonyl isothiocyanates show features which a re interpreted in terms of both cisoid and transoid conformers being p resent. Temperature dependent IR data show that for X = Cl and Br the transoid conformation is more stable while for X = F, MeO and EtO the cisoid form is preferred. The conformeric stabilities and vibrational data are compared with recent results for the corresponding isocyanato species.