Millimeterwave Spectral Studies of Propynal (HCCCHO) Produced by DC Glow Discharge and Ab Initio DFT Calculation

The ground-state (=0) millimeterwave rotational spectrum of propynal (HCCCHO) produced by a DC glow discharge through a low-pressure (~10–20 mTorr) flow of propargyl alcohol (HCCCH2OH) vapor has been observed in the frequency region: 36.0–94.0 GHz. Measured rotational transition frequencies along with the previously reported microwave and millimeterwave transitions were fitted to a standard asymmetric-top Hamiltonian to determine an improved set of rotational and centrifugal distortion constant. Detailed DFT calculations were also carried out with various functional and basis sets to evaluate the spectroscopic constants, dipole moment, and various structural parameters of propynal and compared with the corresponding experimental values.