Abstract
It has been recently demonstrated that there is a high statistical correlation between the relative energies of isomers and their relative abundances in the interstellar medium (ISM). In the present work we use the high-level W2-F12 thermochemical protocol to obtain accurate isomerization energies for a set of 109 H$_x$C$_y$O$_z$ isomers, 18 of which have been observed in the ISM so far. We use our benchmark isomerization energies to (i) rationalize the presence of the isomers that have been detected, and (ii) predict which new isomers are likely to be detected in the future. We find that the energetically most stable isomers of H$_2$C$_3$O (1,2-propadien-1-one), H$_8$C$_3$O (2-propanol), and H$_6$C$_3$O$_2$ (propanoic acid) have not been observed, despite the fact that higher-energy isomers of these chemical formulas have been detected in the ISM. The dipole moments of these isomers are sufficiently large that these species should be observed using microwave spectroscopy techniques.