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Conformational equilibria for 2‐ and 3‐chlorostyrene: Raman and Fourier transform infrared spectra and ab initio calculations
Author(s) -
RibeiroClaro P. J. A.,
TeixeiraDias J. J. C.
Publication year - 1994
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.1250250511
Subject(s) - raman spectroscopy , conformational isomerism , ab initio , chemistry , ab initio quantum chemistry methods , infrared , fourier transform , infrared spectroscopy , analytical chemistry (journal) , spectral line , computational chemistry , crystallography , molecule , physics , organic chemistry , optics , quantum mechanics , astronomy
Ab initio SCF MO calculations at the 3–21G level and the vibrational spectra [Raman and Fourier transform (FT) IR] of liquid‐phase 2‐chloro‐ and 3‐chlorostyrene are reported. For 2‐chlorostyrene, the ab initio calculations predict skew and gauche minima, with an energy difference of 11.5 kJ mol −1 , and no evidence of more than one conformer was found in the liquid‐phase Raman and FTIR spectra. The Raman spectra of liquid 3‐chlorostyrene show pairs of bands whose temperature‐dependent intensities clearly suggest the occurrence of a conformational equilibrium. From these bands, assigned to non‐planar cis and trans conformers, a trans – cis energy difference of 2.3 ± 0.5 kJ mol −1 was obtained for the liquid phase.