ISSN:
0377-0486
Schlagwort(e):
Chemistry
;
Analytical Chemistry and Spectroscopy
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Infrared (4000-50 cm-1) spectra of gaseous, amorphous and crystalline solid ethyl chloroformate, ClCOOCH2CH3, and mid-infrared spectra (4000-500 cm-1) of the chloroformate dissolved in liquefied krypton were recorded. Raman spectra of the liquid and solid phases were investigated from 4000 to 50 cm-1. MP2 and RHF ab initio calculations were carried out using a 6 - 31G* basis set. The calculations show that the compound can occur as the s-cis,trans, the s-cis,gauche, the s-trans,trans and the s-trans,gauche conformers. For each conformer the optimized structural parameters, the vibrational wavenumbers, infrared intensities, Raman scattering activities and potential energy distributions were calculated. Both s-cis conformers were identified in the vibrational spectra of all non-crystalline phases. Evidence for the presence of the s-trans conformers is found in the liquid-phase Raman spectra. The enthalpy difference between the s-cis,gauche and s-cis,trans conformers was determined in the pure liquid phase to be 3.2 ± 0.3 kJ mol-1. Also in the liquid phase, the enthalpy difference between the observed s-trans and the s-cis,trans conformers was determined to be 14.3 ± 0.8 kJ mol-1. Vibrational spectra of the crystalline solid, which contains only the s-cis,trans conformer, showed that ethyl chloroformate can crystallize in two different forms. A complete assignment of the infrared and Raman spectra is proposed.
Zusätzliches Material:
12 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jrs.1250260832
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