Microwave Spectrum of Propiolic Aldehyde

The microwave spectrum of propiolic aldehyde has been studied in the 18—37 Kmc region. Analysis of the ground state spectrum provides the following rotational constants: b=4826.31±0.03 Mc, c=4499.75 ±0.03 Mc, and δ=0.00594±0.0030 Mc, consistent with a planar model. Strong vibrational satellites were observed and fitted, and approximate values of the two lowest vibrational frequencies were found from intensity ratios to be roughly 150 cm—1 and 230 cm—1. The dipole moment of the ground vibrational state is 2.46±0.04D, as determined from quantitative Stark effect studies.