Raman spectra of gaseous and solid methyl- d3-vinyl ether, a re-investigation of the far infrared spectra, and the conformational stability in the gas phase

Abstract

The Raman spectra (3500-40 cm −1) of gaseous and solid methyl- d 3-vinyl ether, CH 2CHOCD 3, have been recorded, and assignments are provided for the observed bands. From the temperature study of the Raman spectrum of CH 2CHOCH 3, the enthalpy difference between the low energy s- cis conformer and the high energy gauche (skew) conformer was found to be 593 ± 32 cm −1 (1.70 ± 0.09 kcal/mol). The far i.r. spectra of both CH 2CHOCH 3 and CH 2CHOCD 3 have been re-investigated at a resolution of 0.1 cm −1 and several new features have been found which were not previously reported. The potential function governing the methoxy torsion was found in cm −1 to be V 1 = −227 ± 134 ( −0.65 ± 0.38 kcal/mol), V 2 = 1307 ± 170 (3.74 ± 0.49 kcal/mol), V 3 = 1475 ± 39 (4.22 ± 0.11 kcal/mol) and V 6 = 7̄5 ± 17 (−0.21 ± 0.05 kcal/mol). The s- cis/ gauche, gauche/ gauche and gauche/ s- cis barriers in cm −1 are 2456 ± 116 (7.02 kcal/mol), 610 ± 57 (1.74 kcal/mol) and 1818 ± 116 (5.20 kcal/mol), respectively. The dihedral angle for the methoxy group of the gauche conformer was determined to be 138°. The barrier to internal rotation of the methyl group is 1333 ± 40 cm −1 (3.81 ± 0.11 kcal/mol) for the s- cis conformer and 523 ± 10 cm −1 (1.50 ± 0.03 kcal/mol) for the gauche conformer. These results are compared to those obtained previously.