Microwave Spectrum and Barrier to Internal Rotation in 2,4-Difluorotoluene

The microwave rotational spectra of 2,4-difluorotoluene (C6H3CH3F2) have been investigated in the ground and first excited torsional state in the frequency ranges 12.4–26.0 and 32.0–37.0 GHz. The true rotational constants for the ground state were determined to beAr= 3070.287 MHz,Br= 1273.842 MHz, andCr= 905.440 MHz. Analysis of theA–Esplittings of some ground torsional state transitions resulted in the values ofV3= 583.002 cal/mole and θa= 16.605°, assumingV6= 0 andIα= 3.2 amu·Å2.