Conformational analysis of 1,3-Dioxole, 1,3-dioxolane, 1,3-dithiolane, and ehtyl nitrite /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1994.
|
| Subjects: | |
| Online Access: | Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | The far-infrared and low-frequency Raman spectra of 1,3-Dioxole have been analyzed. The gas-phase far-infrared spectrum shows a series of eleven singlequantum- jump and three triple-quantum-jump transitions in the 40-330 cm'1 region. The low-frequency Raman spectrum exhibits eight ring-puckering transitions corresponding to Av=2 or 4 transitions in the 160-300 cm'1 region. The ringpuckering potential energy function was determined to be V^cm'1) = 1.59 x10s x4 - 4.18 x 104 x2, where x is the ring puckering coordinate in A. This function indicates that the molecule is puckered with a barrier to planarity of 275 cm'1 and a bending angle of 24°. The unexpected non-planarity of 1,3-dioxole is attributed to the anomeric effect which can be present in molecules with O--C--O linkages. Molecular mechanics calculations utilizing the MM3 parameterization predict a planar structure for this molecule. However, the anomeric effect dictates that each of the =C--O--C--O torsional angles should have a strong tendency to increase from 0° towards 90° in order to optimize n-a* overlap. When the MM3 force field is modified to reflect this by increasing the magnitude of the two-fold torsional potential energy term V2 to -5.965 kcal/mole, a reasonably good agreement between the experimental and molecular mechanics potential functions can be obtained. The gas-, liquid-, and solid-phase mid-infrared and Raman spectra of 1,3- dioxole have also been analyzed. A satisfactory vibrational assignment of the twenty-one fundamental vibrations has been achieved. The low-frequency far-infrared spectra of 1,3-dioxolane and 1,3-dithiolane have been examined. It was concluded that 1,3-dioxolane is a nearly free pseudorotor with a pseudorotational barrier which is less than 50 cm'1 while 1,3- dithiolane exhibits hindered pseudorotation with a moderate barrier to pseudorotation. Ethyl nitrite-d0 and -d5 have been synthesized. Band contour simulations of the N = 0 stretching bands observed in the gas-phase mid-infrared spectra of the deuterated species indicate that the Q branch at 1670.5 cm'1 can be ascribed to the tram,gauche rotational isomer. The band at 1611.5 cm 1, on the other hand, may result from the superposition of two conformers. |
|---|---|
| Item Description: | "Major subject: Chemistry." Vita. |
| Physical Description: | xiv, 140 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |