Microwave Spectrum, Barrier to Internal Rotation, Structural Information, and Quadrupole Coupling of 1hyphen;Chlorohyphen;1,1hyphen;difluoroethane

摘要

The microwave spectra of two isotopic species, CH3sngbnd;CF235Cl and CH3sngbnd;CF237Cl, have been investigated in the region 8ndash;40 GHz. A partial determination of structure strongly suggests a shortening in Csngbnd;C, Csngbnd;F, and Csngbnd;Cl distances compared to singly or doubly substituted fluorohyphen; 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 4400thinsp;plusmn;thinsp;100 cal/mole. The chlorine quadrupole coupling tensor is nearly symmetric about the Csngbnd;Cl bond. This implies a pitfall in the application of simple resonance theory to molecules of this type; with simple resonance theory the shortened Csngbnd;Cl bond is explained in terms of considerable doublehyphen;bond character for the Csngbnd;Cl bond, which in turn would call for an asymmetrickhgr;tensor.