Bar plot of the relative abundances of CH₃COCH₃/ C₂H₅CHO and CH₃CHO/c-C₂H₄O from Table 1. The observations are indicated by color bars, while the chemical predictions are shown by white bars with different circle sizes. The two lower limits derived by Belloche et al. (2013) for CH₃COCH₃/C₂H₅CHO are illustrated by upward arrows. The range of CH₃CHO/ c-C₂H₄O ratios determined in ten sources by Ikeda et al. (2001) is indicated by the hatched area. For the CH₃CHO/ c-C₂H₄O ratio from Belloche et al. (2013), we used the average value of the column densities of the rotational and first torsionally (v_t = 1) excited states of acetaldehyde.