The microwave spectrum and potential function of propanal
Abstract
The potential function for internal rotation of the aldehyde group in propanal has been determined. All available microwave and far-infrared data are fitted to the potential V(α)=½ [graphic omitted] Vn(1 – cos nα) and where (in cm–1)V1= 251(2), V2= 736(8), V3= 550(4), V4=–179(5) and V5=–7(4). The energy difference between the two stable conformers has been redetermined from microwave relative intensities to be ΔW(gauche–cis)= 420(27) cm–1. Torsional fundamentals measured in the infrared have also been used in the potential function calculation. Isotopic data have been measured providing insight into the torsional motion in CH3CH2CH18O and CH3CH2CDO. The resulting potential is compared with some isoelectronic molecules. The dipole moment of gauche propanal has been measured as 2.864(8) D orientated within 0.6° of the CO bond.