First observation of the rotational spectrum of the bromomethyl radical, CH2Br

The first high resolution rotational spectrum of the bromomethyl radical in the gas phase has been observed. The radical was produced in a fast flow system by hydrogen abstraction of CH3Br by Cl or F atoms obtained from a 2450 MHz microwave discharge in Cl2 or in CF4, respectively. The rotational, quartic centrifugal distortion constants have been obtained as well as the electron spin–rotation interaction constants. The small positive inertial defect, Δ0 = 0.032 amu A2 deduced from the rotational constants of the CH279Br species clearly indicates that the radical is planar in its ground vibronic state.