The Rotational Spectrum of Acetone: Deuterated Species, Internal Rotation, and Structure

Abstract The microwave and millimeter-wave rotational spectra of CH 3 COCH 2 D, CD 3 COCD 2 H, and CD 3 COCD 3 have been measured. For these three isotopic species the rotational constants, the centrifugal distortion constants and the three internal rotation parameters (barrier, methyl top moment of inertia, and angle between the internal rotation axis and the a inertial axis) have been accurately determined using two computer programs based on the Internal Axis Method. The decrease of the potential barrier upon deuteration is evident. The substitution coordinates of the hydrogen atoms could also be determined. It is confirmed that the in-plane methyl hydrogen has a position cis with respect to the oxygen atom.