INFRARED AND RAMAN-SPECTRA, CONFORMATIONAL STABILITY, VIBRATIONAL ASSIGNMENT, AND AB-INITIO CALCULATIONS OF CHLOROMETHYL ISOCYANATE

The infrared (3200 to 400 cm(-1)) and Raman (3200 to 20 cm(-1)) spectr a of gaseous and solid chloromethyl isocyanate, ClCH2NCO, have been re corded. Also, the Raman spectrum of the liquid and qualitative depolar ization values have been obtained. Additionally, infrared spectra have been recorded at various temperatures with the sample dissolved in li quid xenon. An assignment of the fundamental vibrations based on the i nfrared band contours, depolarization values and group frequencies is given and discussed. This assignment is supported by a normal coordina te analysis utilizing a force field obtained from ab initio calculatio ns with the RHF/6-31G basis set as well as with electron correlation, MP2/6-31G. A complete equilibrium geometry has been determined by ab initio gradient calculations employing the RHF/3-21G, RHF/6-31G* and MP2/6-31G basis sets, The potential surface governing internal rotat ion about the C-N bond is calculated to be consistent with a single mi nimum corresponding to a structure having the chlorine atom cis or nea r-cis to the NCO moiety. These results are compared with the correspon ding quantities for ethyl isocyanate, CH3CH2NCO, and related compounds .