Spectroscopic and theoretical investigation of the potential energy surfaces of selected cyclic and bicyclic molecules /
The vibrational potential energy surfaces of several different molecules were investigated using far-infrared, Raman, and fluorescence spectroscopies, as well as ab initio calculations. The far-infrared spectrum of vinylene carbonate shows five closely spaced bands near 233 cm⁻¹, characteristic o...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2003.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765867051&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The vibrational potential energy surfaces of several different molecules were investigated using far-infrared, Raman, and fluorescence spectroscopies, as well as ab initio calculations. The far-infrared spectrum of vinylene carbonate shows five closely spaced bands near 233 cm⁻¹, characteristic of a nearly harmonic ring-puckering potential energy function. This shows the molecule to be much more rigid than the similar 3-cyclopenten-1-one due to [?]-bonding interactions involving the oxygen atoms adjacent to the carbonyl group. The far-infrared spectrum resulting from the ring-puckering vibration of 2,3-dihydrofuran (23DHF) was recorded. Analysis of the spectra and incorporating a kinetic energy expansion yielded a potential function, which has a barrier to planarity of 93 cm⁻¹ and energy minima at dihedral angles of ±22⁰. The values agree well with the ab initio values of 96 cm⁻¹ and ±23⁰. The high-temperature vapor-phase Raman spectrum of 1,3-cyclohexadiene shows nine transitions resulting from the ring-twisting mode between 116-200 cm⁻¹. Far-infrared absorption bands confirm five of these transitions. A one-dimensional potential energy function with a barrier of 1132 cm⁻¹ fits the data well. Ab initio calculations predict barriers in the 1197 - 1593 cm⁻¹ range. Raman and infrared combination bands also verify the assignments. The twisting angles were determined to be 9.1[?] and 30.1[?]. The infrared and Raman spectra of bicyclo[3.3.0]oct-1,5-ene in the vapor and liquid phases have been recorded and analyzed. Ab initio calculations predict the trans C₂[h] conformational energy to be 65 to 229 cm-1 higher than that of the cis C₂[v] conformer. A model for calculating the kinetic energy expansions was developed for this molecule and used together with the potential energy surface to calculate the quantum states and spectroscopic transitions for the puckering motions. The laser-induced fluorescence spectra (FES) and dispersed fluorescence (SVLF) spectra of jet-cooled 1,2-dihydronaphthalene have been analyzed to investigate the ring inversion process in both the S₀ and S₁([?],[??]*) excited state. Ultraviolet absorption, infrared, and Raman spectra were also recorded to complement the analyses. Ab initio calculations predict the inversion process to involve four out-of-plane ring motions, and linear combinations of these were made to model the inversion process. The data show the barrier to inversion in the ground state to be 1363 ± 100 cm⁻¹ (the ab initio value is 1524 cm⁻¹). The barrier increases substantially in the excited state. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xix, 204 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 199-203). |