Laboratory rotational spectroscopy and astronomical search for 2-ethylacrolein

The rotational spectrum of 2-ethylacrolein was investigated by pulsed jet Fourier transform microwave spectroscopy complementary with quantum chemical calculations. The rotational spectra of both conformers cis and gauche and their all mono-substituted ¹³C and ¹⁸O isotopologues were measured and assigned in natural abundance, allowing the accurate structural determinations on their heavy-atom skeletons. The relative population ratio of cis to gauche in pulsed jets was estimated to be ≈ 3:1. With the accurate rotational transition frequencies, radio astronomical searches toward the massive star-forming region Sgr B2(N) were carried out by using the Shanghai Tianma 65 m radio telescope. No transition lines belonging to 2-ethylacrolein were detected, the upper limits of column densities for cis and gauche were derived to be 7.52 × 10¹³ cm⁻² and 1.29 × 10¹⁵ cm⁻², respectively.