Low-resolution microwave spectroscopy: A new band type

The effects of relaxing two constraints on an earlier force field for benzene and fluorobenzenes have been explored. If the CC/CC ortho, meta, and para interaction constants are allowed to vary independently, they take the values 62, ?34, and 48 N m^?1, respectively. The interesting features of the earlier field are retained with the possible exception that the dependence of the CC stretching constant is less clearly dependent on fluoro substitution on the bond. An attempt to use more reasonable geometries than the regular hexagonal geometry assumed hitherto produced no improvement in the fit and did not alter the field significantly.