Pseudorotation of cyclopentane and its deuteriated derivatives
The gas-phase mid-infrared Raman spectra of cyclopentane, cyclopentane-d, cyclopentane-1,1-d/sub 2/, cyclopentane-1,1,2,2,3,3-d/sub 6/, and cyclopentane-d/sub 10/ have been recorded and analyzed in order to investigate the vibrational potential energy surface associated with the pseudorotational and radial motions. For cyclopentane two separate combination band series involving the pseudorotation and a CH/sub 2/ deformation or a CH/sub 2/ wag were observed. The spacings in those series were about 5.4 and 4.1 cm/sup -1/, respectively. Similar series with spacings of about 5.0 and 3.7 cm/sup -1/ were observed for the d/sub 1/ species. Cyclopentane-d/sub 10/ shows one combination band series near 1000 cm/sup -1/ with a spacing of 4.0 cm/sup -1/. In addition to these combination bands, pseudorotational fine structure was observed in the overtone region of the radial band (420-560 cm/sup -1/ for the different isotopic species). Previously, the absorption in this region had been mistakenly assigned to a vibrational fundamental. The radial band itself was observed for each species in its Raman spectrum. Computational methods for calculating the energy levels for this type of two-dimensional problem have been developed. Reduced mass calculations for each isotopic species have also been carried out. The observed spectra have been analyzed both by using a one-dimensional approximation model and by calculating a two-dimensional potential energy surface. The results demonstrate that the pseudorotation in cyclopentane is relatively unhindered and that the barrier is planarity is about 5.5 kcal/mol (values ranging from 1808 to 2090 cm/sup -1/ were calculated by using different models for the various isotopic species).
- Research Organization:
- Texas A and M Univ., College Station (USA)
- OSTI ID:
- 7148543
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 92:5; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Thermodynamics of cyclopentane, methylcyclopentane and 1,cis-3-dimethylcyclopentane: verification of the concept of pseudorotation
Vibrational optical activity in deuteriated phenylethanes
Related Subjects
400201* -- Chemical & Physicochemical Properties
ALKANES
CYCLOALKANES
DATA
DEUTERIUM COMPOUNDS
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
HAMILTONIANS
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
INFRARED SPECTRA
MATHEMATICAL OPERATORS
MECHANICS
NORMAL-MODE ANALYSIS
NUMERICAL DATA
ORGANIC COMPOUNDS
PENTANE
QUANTUM MECHANICS
QUANTUM OPERATORS
RAMAN SPECTRA
ROTATIONAL STATES
SPECTRA
VIBRATIONAL STATES