Microwave Spectrum, Barrier to Internal Rotation, Structural Information, and Quadrupole Coupling of 1-Chloro-1,1-difluoroethane

The microwave spectra of two isotopic species, CH3–CF2 35Cl and CH3–CF2 37Cl, have been investigated in the region 8–40 GHz. A partial determination of structure strongly suggests a shortening in C–C, C–F, and C–Cl distances compared to singly or doubly substituted fluoro- or chloroethanes. Vibratio...

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Bibliographic Details
Published in:The Journal of chemical physics 1968-01, Vol.49 (9), p.4160-4167
Main Authors: Graner, Georges, Thomas, Clarence
Format: Article
Language:English
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Summary:The microwave spectra of two isotopic species, CH3–CF2 35Cl and CH3–CF2 37Cl, have been investigated in the region 8–40 GHz. A partial determination of structure strongly suggests a shortening in C–C, C–F, and C–Cl distances compared to singly or doubly substituted fluoro- or chloroethanes. Vibrationally excited states were observed showing doublets due to the hindered internal rotation of the methyl group. An analysis of these doublets gives a barrier to internal rotation of 4400 ± 100 cal/mole. The chlorine quadrupole coupling tensor is nearly symmetric about the C–Cl bond. This implies a pitfall in the application of simple resonance theory to molecules of this type; with simple resonance theory the shortened C–Cl bond is explained in terms of considerable double-bond character for the C–Cl bond, which in turn would call for an asymmetric χ tensor.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.1670730