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Raman and infrared spectra, conformational stability from temperature‐dependent Fourier transform infrared spectra of xenon solutions, ab initio calculations and vibrational assignment of 4‐chlorobut‐1‐yne
Author(s) -
Durig James R.,
Drew Barry R.,
Guirgis Gamil A.
Publication year - 2001
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.740
Subject(s) - conformational isomerism , raman spectroscopy , xenon , chemistry , infrared , ab initio , ab initio quantum chemistry methods , infrared spectroscopy , molecule , crystallography , computational chemistry , organic chemistry , physics , optics
The Raman spectra (3400–10 cm −1 ) of liquid and solid and the infrared spectra (3400–50 cm −1 ) of gaseous, xenon solution and solid 4‐chlorobut‐1‐yne, CH 2 ClCH 2 CCH, were recorded. These data indicate that the molecule exists in the anti (the C—Cl bond is trans to the CC bond) and the gauche conformations in the vapor and liquid and that both conformers persist in the solid with an indication that the gauche conformer may be more stable in this physical state. From a variable‐temperature infrared study of the xenon solution, the anti conformation has been determined to be more stable than the gauche form by 147 ± 10 cm −1 (1.76 ± 0.12 kJ mol −1 ). From these data it is estimated that 50% of the sample is in the gauche form at ambient temperature. The optimized geometries, conformation stabilities, harmonic force fields, Raman activities, depolarization ratios and infrared intensities were obtained from MP2/6–31G(d) ab initio calculations with full electron correlation. These quantities were compared with the corresponding experimental quantities when appropriate. Equilibrium geometries and energies for both conformers were obtained from ab initio MP2/6–311 + G( d , p ) and MP2/6–311 + G(2 d , 2 p ) calculations. Vibrational assignments for the 24 normal modes for both the anti and gauche conformers are proposed. These experimental and theoretical results are compared with the corresponding quantities for some similar molecules. Copyright © 2001 John Wiley & Sons, Ltd.