Computational Protocol for the Identification of Candidates for Radioastronomical Detection and Its Application to the C3H3NO Family of Isomers

Abstract

The C3H3NO family of isomers is relevant in astrochemistry, even though its members are still elusive in the interstellar medium. To identify the best candidate for astronomical detection within this family, we developed a new computational protocol based on the minimum-energy principle. This approach aims to identify the most stable isomer of the family and consists of three steps. The first step is an extensive investigation that characterizes the vast number of compounds having the C3H3NO chemical formula, employing density functional theory for this purpose. The second step is an energy refinement, which is used to select isomers and relies on coupled cluster theory. The last step is a structural improvement with a final energy refinement that provides improved energies and a large set of accurate spectroscopic parameters for all isomers lying within 30 kJ mol−1 above the most stable one. According to this protocol, vinylisocyanate is the most stable isomer, followed by oxazole, which is about 5 kJ mol−1 higher in energy. The other stable species are pyruvonitrile, cyanoacetaldehyde, and cyanovinylalcohol. For all of these species, new computed rotational and vibrational spectroscopic data are reported, which complement those already available in the literature or fill current gaps.

On the General Mechanism for the Gas-phase Reaction of Methanimine with a Radical Species in the Interstellar Medium: Some Failures and an Important Success

“…The PE, PZ, and PN products of the CH 2 NH + C 3 N reaction belong to the C 4 H 2 N 2 family of compounds, which is of astrochemical relevance (Marchione et al 2022), but they have not previously been studied. Investigations on the entire isomeric family are currently in progress by exploiting a protocol recently implemented (Alessandrini et al 2023). To enable the first experimental characterization of Z-HCNCHCCCN, E-HCNCHCCCN, and CH 2 NCCCN by means of rotational spectroscopy, we have also reported accurate predictions for their rotational constants.…”

Stereo-electronic factors influencing the stability of hydroperoxyalkyl radicals: transferability of chemical trends across hydrocarbons and ab initio methods

“…12 Further, when it is challenging to associate experimental spectra of transient species with multiple potential isomers, computational findings provide valuable insights. 18,19 For modelling low-temperature combustion reactions of small hydrocarbons, coupled cluster singles doubles with perturbative triples approximation, CCSD(T), has yielded highly accurate predictions. 20,21 For larger molecules, composite wavefunction theories have demonstrated the best computational efficiency for reproducing experimental formation enthalpies of stable species [22][23][24][25][26][27] and for accurate modelling of barrier heights.…”