Raman and infrared spectra, conformational stability, normal coordinate analysis, vibrational assignment, and ab initio calculations of trans-3-pentenenitrile

摘要

The Raman (3200-20 cm(-1)) spectra of liquid and solid trans-CH3CH=CHCH2CN, and the infrared (3200-30 cm(-1)) spectra of gaseous and solid trans-3-pentenenitrile have been recorded. The spectra of the fluid phases are consistent with two stable conformers in equilibrium at ambient temperature. The mid-infrared spectra of the sample dissolved in liquid xenon as a function of temperature (- 100 to -55 degreesC) have been recorded. Utilizing two conformer pairs, the enthalpy difference has been determined to be 205 +/- 7 cm(-1) (2.45 +/- 0.08 kJ/mol) with the syn conformer being the more stable form. Vibrational assignments For the 33 normal modes for the syn conformer and several of those for the gauche form are proposed. The structural parameters, dipole moments, conformational stability, and vibrational frequencies have been determined from ab initio calculations. The predicted conformational stability is consistent with the experimental results. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 28]