Vibrational spectroscopy and conformational analysis of small ring molecules /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Potential energy surfaces for the low-frequency vibrations of several six-membered and bicyclic rings were calculated in order to determine the low energy conformations of the molecules. Far-infrared and Raman spectral data were used for the calculations. Vector models were developed to calculate kinetic energy (reciprocal reduced mass) expressions. The far-infrared and Raman spectra of several oxygen analogues of cyclohexene have been reported. The data has been reanalyzed in terms of two-dimensional vibrational potential energy surfaces for the ring-bending and ring-twisting vibrations. In each case, the twisted (half-chair) conformations have the lowest energy. The bent (boat) conformations were determined to be saddle points in the surfaces with energies 3120 to 3830 cm ⁻¹ above the energy minima. The barriers to planarity range from 3500 to 4130 cm⁻¹.The angles determined for the twisting of the rings are in reasonable agreement with microwave results. The far-infrared and Raman spectra of 5,6-dihydro-2H-thiopyran was recorded and analyzed. Two series of sharp bands were observed at 139 cm⁻¹ and 235 cm⁻¹ in the infrared spectrum for the out-of-plane ring-bending and the ring-twisting vibrations, respectively. A detailed energy level diagram was determined, and the two-dimensional potential energy surface was calculated. The minimum energy on the surface occurs when 5, 6-dihydrothiopyran is twisted by 37.8°. The lowest energy bent conformation corresponds to a saddle point 4130 cm⁻¹ above the twisted conformation on the potential energy surface. Two silicon-containing cyclohexene analogues, silacyclohex-2-ene and silacyclohex-2-ene-1,1-d₂, were synthesized, and their far-infrared and Raman spectra were recorded. Three series of sharp bands were observed below 300 cm⁻¹: the ring-bend (113 and 106 cm⁻¹) the single bond ring-twist (238 and 233 cm⁻¹), and the double bond ring-twist (303 and 287 cm⁻¹), for silacyclohex-2-ene and silacyclohex-2-ene-1,1-d₂, respectively. Energy level diagrams for the ring-bending and ring-twisting vibrations were determined, and preliminary two-dimensional potential energy functions were considered. The high resolution far-infrared spectra of bicyclo(3.2.0) hept-1(5)-ene revealed many bands that had not been previously observed. Several possible assignments for the bands in the ring-bending series were considered, and corresponding one-dimensional potential functions were determined. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xv, 155 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |