Blue and green bars show the column density ratios for O- and N-bearing molecules that are more complex than four atoms toward the CC core and C8 (C8 1.″5), respectively. We use the values given in Table 4 for C8 1.″5 and the first velocity component toward the CC core. Error bars indicate formal uncertainties and arrows indicate lower bounds. We also show abundance ratios measured toward six HMCs from the literature (Sgr B2 sources from Belloche et al. 2013, NGC 7538 from Öberg et al. 2014, and the rest of the sources from Bisschop et al. 2007). The black dashed line and error bar indicate the [HNCO]/[CH₃OH] ratio obtained toward the CC core using the column density of HNCO given in Figure 16 associated with the second velocity component.