Conformational and structural analyses of some alcohols and amines of molecules with low frequency large amplitude anharmonic vibrations.

摘要

The infrared and Raman spectra of compounds with hydroxyl and amino functional groups, as well as some with cyclic skeletal structures have been recorded of the gas and in condensed phases. Temperature dependent infrared spectra in xenon and krypton solutions were also recorded. A complete vibrational assignment, conformational stability determination and adjusted r0 parameters have been obtained for each of the most stable conformers and in some cases for lesser stable conformers. The results of these investigations were supported by ab initio predicted infrared intensities and depolarization ratios, band contours and conformational stabilities. Normal coordinate calculations were carried out for all of the molecules. From these calculations potential energy distributions for all the fundamentals were predicted for each molecules from which approximate descriptions of the vibrations were ascertained.;Cyclobutanes substituted with asymmetric rotor such as hydroxyl and amine groups have four possible conformers. In case of cyclobutanol two of the four possible stable conformers have been confidently identified and their order of stabilities has been experimentally determined whereas three out of the four conformers were experimentally determined for cyclobutylamine. For halogen substituted cyclobutanes only two possible determined for cyclobutylamine. For halogen substituted cyclobutanes only two possible conformers exist and the enthalpy difference between the more stable equatorial conformer and the axial form has been determined for fluoro-, chloro-, and bromocyclobutane.;For fluorocyclopentane only a single twist conformer was found which is at a variance to previously reported structures of both envelope-equatorial and envelope-axial conformers or only a single envelope-equatorial conformer. Thus, fluorocyclopentane provides a unique example of pseudorotation for five member rings. However for cyanocyclopentane both the equatorial and axial forms were observed. The conformational stabilities, adjusted r0 structural parameters and other scientific information are discussed and compared to the corresponding properties of some similar molecules based upon their functional groups and molecular structure.