Millimeter-Wave Rotational Spectra of trans-Acrolein (Propenal) (CH2CHCOH): A DC Discharge Product of Allyl Alcohol (CH2CHCH2OH) Vapor and DFT Calculation

Millimeter-wave rotational spectrum of trans-acrolein (propenal) (CH2CHCOH) produced by applying a DC glow discharge through a low-pressure (~10–20 mTorr) flow of allyl alcohol (CH2CHCH2OH) vapor has been observed in the ground and several excited torsional states in the frequency region: 60.0–99.0 GHz. A least-square analysis of the measured and previously reported rotational transition frequencies has produced a set of rotational and centrifugal distortion constants for the ground as well as excited torsional states. 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 the trans conformer of propenal for the ground state and compared with their corresponding experimental values. A linear variation of the inertia defect values with torsional quantum number (=0,1,2,3) demonstrates that the equilibrium configuration of trans-propenal is planar.