2-hydroxyprop-2-enal millimetre-wave spectroscopy

The rotational spectrum of 2-hydroxyprop-2-enal was measured and analysed in the frequency regions of 128-166GHz and 285-329GHz. The interstellar exploration towards IRAS 16293-2422 was based on the Atacama Large Millimeter/submillimeter Array (ALMA) data of the Protostellar Interferometric Line Survey. We also used the imaging spectral line survey ReMoCA performed with ALMA toward Sgr B2(N) to search for 2-hydroxyprop-2-enal in the interstellar medium.

We modelled the astronomical spectra under the assumption of local thermodynamic equilibrium. We provide laboratory analysis of hundreds of rotational transitions of 2-hydroxyprop-2-enal in the ground state and the lowest lying excited vibrational state. We report its nondetection towards IRAS16293 B. The 2-hydroxyprop-2-enal/3-hydroxypropenal abundance ratio is estimated to be <~0.9-1.3 in agreement with the predicted value of ~1.4.

We also report the nondetection of 2-hydroxyprop-2-enal toward the hot molecular core Sgr B2(N1). We did not detect the related aldehydes 2-hydroxypropanal and 3-hydroxypropenal either. We find that these three molecules are at least 9, 4, and 10 times less abundant than acetaldehyde in this source, respectively.

Despite the nondetections of 2-hydroxyprop-2-enal, the results of this work represent a significant improvement on previous investigations in the microwave region and meets the requirements for further searches of this molecule in the interstellar medium.