Raman and infrared spectra, conformational stability, barriers to internal rotation, ab initio calculations, and vibrational assignments of some halopropenes and substituted dimethyl ether molecules

The far infrared spectrum of gaseous 3-bromopropene has been recorded from 350 to 35 cm{dollar}sp{lcub}-1{rcub}.{dollar} The asymmetric torsional potential function governing internal rotation about the C-C bond has been determined. This potential function gives cis to gauche, gauche to gauche and gauche to cis barriers of 749, 770 and 986 cm{dollar}sp{lcub}-1{rcub},{dollar} respectively.; The Raman spectra of gaseous, liquid and solid and infrared spectra of gaseous and solid 3-iodopropene have been recorded. From a study of the Raman spectrum of the liquid at variable temperatures, a value of 648 {dollar}pm{dollar} 81 cm{dollar}sp{lcub}-1{rcub}{dollar} has been determined for the enthalpy difference between the higher energy cis and preferred gauche conformers. The potential is consistent with a dihedral angle of 113.0{dollar}spcirc{dollar} for the gauche conformer, cis to gauche, gauche to gauche, and gauche to cis barriers of 160, 904, and 738 cm{dollar}sp{lcub}-1{rcub}.{dollar}; The Raman spectra of gaseous, liquid and solid and infrared spectra of gaseous and solid 3-methyl-1-butene have been recorded. From studies of the Raman spectrum of the gas with variable temperatures the trans conformer has been determined to be more stable than the gauche form by 155 {dollar}pm{dollar} 31 cm{dollar}sp{lcub}-1{rcub}{dollar} (443 {dollar}pm{dollar} 89 cal/mol). Similar studies for the liquid indicate that the two conformers are nearly equivalent in energy and for the annealed solid only the gauche conformer persists.; The far infrared spectrum of cyanomethyl methyl ether in the gas phase has been recorded. From the potential function, the trans to gauche, gauche to gauche and gauche to trans barriers are determined to be 522, 1592, and 951 cm{dollar}sp{lcub}-1{rcub},{dollar} respectively. A complete vibrational assignment is proposed for a gauche/trans equilibrium in the gas and liquid phases from the Raman and infrared spectra obtained for the gas, liquid and solid phases, but in the solid state only the gauche conformer remains.; The Raman spectra of gaseous, liquid and solid and the infrared spectra of gaseous and solid methylpropargyl ether have been recorded. From the potential function, the trans to gauche, gauche to gauche and gauche to trans barriers are determined to be 664, 1831, and 1021 cm{dollar}sp{lcub}-1{rcub},{dollar} respectively. A complete vibrational assignment is proposed for a gauche/trans equilibrium in the gas and liquid phases and the gauche conformer is the only rotamer present in the annealed solid.