ISSN:
0377-0486
Schlagwort(e):
Chemistry
;
Analytical Chemistry and Spectroscopy
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The Raman (3200-10 cm-1) and infrared (3150-50 cm-1) spectra of allyl cyanide, CH2=CHCH2CN, were recorded for the gas and solid phases. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. Both the cis and gauche conformers are present in the gas and liquid phases with the cis conformer being the more stable rotamer and the only conformer present in the annealed solid. The fundamental asymmetric torsion of the cis conformer has been observed in the far-infrared spectrum of the gas at 141.3 cm-1 with three excited states falling to lower wavenumbers. The corresponding fundamental for the gauche conformer has been observed in the Raman spectrum of the gas at ca. 102 cm-1. From temperature-dependent studies of the Raman spectrum of the liquid, three pairs of conformer peaks have been used to determine the ΔH value of 245 ± 6 cm-1 (707 ± 17 cal mol-1), with the cis conformer the most stable rotamer. Additionally, a variable-temperature study of the infrared spectrum of the sample dissolved in liquified xenon gives a ΔH of 336 ± 61 cm-1 (961 ± 175 cal mol-1), which should closely represent the ΔH value for the gas. Utilizing the torsional transitions, the enthalpy difference and the gauche dihedral angle, the potential function governing the conformational interchange was determined. A complete vibrational assignment is proposed for the cis conformer and several fundamentals are identified for the gauche rotamer based on infrared band contours, Raman depolarization data, group wavenumbers, relative intensities and normal coordinate calculations. The experimental conformational stability, barriers to internal rotation, structural parameters and fundamental vibrational wavenumbers are compared with those obtained from ab initio gradient calculations employing the RHF/3-21G, RHF/6-31G* and/or MP2/6-31G* basis sets and to the corresponding quantities obtained for some similar molecules.
Zusätzliches Material:
13 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jrs.1250251203
Permalink
