Taken in part from the theses of I. D. Darkhalil and J. J. Klaassen, which will be submitted in partial fulfillment of the Ph.D. degrees.
Conformational and structural studies of n-propylamine from temperature dependent Raman and far infrared spectra of xenon solutions and ab initio calculations
Article first published online: 23 JUN 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 43, Issue 9, pages 1329–1336, September 2012
How to Cite
Durig, J. R., Darkhalil, I. D., Klaassen, J. J., Herrebout, W. A., Dom, J. J. J. and van der Veken, B. J. (2012), Conformational and structural studies of n-propylamine from temperature dependent Raman and far infrared spectra of xenon solutions and ab initio calculations. J. Raman Spectrosc., 43: 1329–1336. doi: 10.1002/jrs.3163
- Issue published online: 17 SEP 2012
- Article first published online: 23 JUN 2012
- Manuscript Revised: 15 DEC 2011
- Manuscript Accepted: 15 DEC 2011
- Manuscript Received: 6 NOV 2011
- conformational stability;
- vibrational assignment;
- xenon solutions
The Raman and infrared spectra (4000 to 50 cm–1) of the gas, liquid or solution, and solid have been recorded of n-propylamine, CH3CH2CH2NH2. Variable temperature (−60 to −100 °C) studies of the Raman (1175 to 625 cm–1) and far infrared (600 to 10 cm–1) spectra dissolved in liquid xenon were carried out. From these data, the five possible conformers were identified and their relative stabilities obtained with enthalpy difference relative to trans–trans (Tt) for trans–gauche (Tg) of 79 ± 9 cm–1 (0.9 ± 0.1 kJ/mol); for Gg of 91 ± 26 cm–1 (1.08 ± 0.3 kJ/mol); for Gg′ of 135 ± 21 cm–1 (1.61 ± 0.2 kJ/mol); for Gt of 143 ± 11 cm–1 (1.71 ± 0.1 kJ/mol). The percentage of the five conformers is estimated to be 18% for the Tt, 24 ± 1% for Tg, 23 ± 3% for Gg, 18 ± 1% for Gg′ and 18 ± 1% for Gt at ambient temperature. The conformational stabilities have been predicted from ab initio calculations utilizing several different basis sets up to aug-cc-pVTZ from both second-order Møller–Plesset (MP2, full) and density functional theory calculations by the Becke, three-parameter, Lee–Yang–Parr method. Vibrational assignments were provided for the observed bands for all five conformers, which are supported by MP2(full)/6-31G(d) ab initio calculations to predict harmonic force constants, wavenumbers, infrared intensities, Raman activities and depolarization ratios for both conformers. Estimated r0 structural parameters were obtained from adjusted MP2(full)/6-311+G(d,p) calculations. The results are discussed and compared with the corresponding properties of some related molecules. Copyright © 2012 John Wiley & Sons, Ltd.