The microwave spectrum of the chloromethyl radical, CH2Cl

Abstract

The gas phase pure rotational spectrum of the chloromethyl radical, CH2Cl, has been observed for the first time in the millimetre wave region using a source frequency modulation microwave spectrometer equipped with a 1 m long free space absorption cell. The radical was generated by the reaction of CH3Cl with 2450-MHz microwave discharge products of CF4. The a-type R-branch transitions have been observed with resolved fine and hyperfine components for both the 35Cl and 37Cl isotopic species in the ground vibrational state. The small positive inertial defect. Δ0 = 0.0333 amu Å2, calculated from the rotational constants obtained for the 35Cl species indicates that the radical is planar in the ground vibronic state. The observed fine and hyperfine interaction constants are consistent with 2B1 symmetry, i.e., with the unpaired electron occupying a pπ orbital extending perpendicular to the molecular plane.