Knowledge Bank

The microwave spectra of methyl $fluoroformate-d3,CD3OC(o)F$, and $methylfluoroformate-d2,CD2HOC(O)F$, have been recorded from 18.0 to 40.0 GHz. The rotational spectra have been assigned and the rotational constants have been calculated. The determined structural parameters are compared to those for methyl formate and methyl chloroformate. The barrier to internal rotation of the methyl group has been calculated from the A-E splitting observed in the microwave spectrum. This value is compared to values obtained from the far infrared spectrum of methyl fluoroformate in the gaseous state and ab initio calculations at the $6-3lG\ast$ level.