A SPECTROSCOPIC STUDY OF MODEL URETHANES

The synthesis, far infrared spectra, temperature-dependent mid-infrare d spectra in the carbonyl and NH stretching regions and the Fourier tr ansform Raman spectra are reported for polycrystalline samples of thre e small diurethanes, 1,3-phenyl di(carbamic acid methyl ester), 2,6-to luene di(carbamic acid methyl ester) and 2,4-toluene di(carbamic acid methyl ester). An ab initio geometry optimization is reported for meth yl N-phenyl carbamate using STO-3G and 3-21G basis sets, and for the t hree small diurethanes by molecular mechanics methods using the Dreidi ng I force field. The results suggest that, in isotropic surroundings, only a very small number of the 256 possible conformers of the uretha ne groups in the three small diurethanes contribute appreciably to the structure.