Fractional abundances with respect to H₂ of different C₃H₆O₂ isomers sorted by increasing relative energy. The total dipole moment for each molecule (computed at the B2PLYP-D3/aug-cc-pVTZ level) is included. We used the same color-code as that in Fig. 1: new first detections in the ISM are shown in red, tentative detections in orange, non-detections in purple (upper limits indicated with black arrows), and previous detections toward different sources in black.