| Abstrakt: |
The far-infrared spectrum of gaseous 2-chloropropenoyl fluoride, CH2 CClCFO, has been recorded at a resolution of 0.10 cm-1 in the region of 350–35 cm-1. The fundamental asymmetric torsional frequencies of the more stable s-trans (two double bonds oriented trans to one another) and the high energy s-cis conformations have been observed at 67.80 and 49.96 cm-1, respectively, each with several excited states falling to lower frequencies. From these data the asymmetric torsional potential function governing the internal rotation about the C–C bond has been determined. The potential coefficients are V1 =-125±1, V2 =1586±6, V3 =375±2, V4 =-36±2, and V5 =-65±1 cm-1. The s-trans to s-cis and s-cis to s-trans barriers have been determined to be 1755 and 1570 cm-1, respectively, with an energy difference between the conformations of 185±9 cm-1 (529±26 cal/mol). From studies of the Raman spectrum at variable temperatures, the conformational enthalpy difference has been determined to be 176±40 cm-1 (503±114 cal/mol) and 625±51 cm-1 (1787±146 cal/mol) for the gas and liquid, respectively. A complete assignment of the vibrational fundamentals observed from the infrared spectra (3500–50 cm-1) of the gas and solid and the Raman spectra (3200–10 cm-1) of all three physical states is proposed. All of these data are compared to the corresponding quantities obtained from ab initio Hartree–Fock gradient calculations employing both the 3-21G* and 6-31G* basis sets. Additionally, complete equilibrium geometries have been determined for both rotamers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules. [ABSTRACT FROM AUTHOR] |
