Galactocentric gradients of molecular ratios. The plot shows the trend of the ratios between CO molecule products (i.e., HCO⁺, H¹³CO⁺, HCO, CH₃OH, and H₂CO) and c-C₃H₂, as a function of galactocentric radius (R_GC). The 1σ error bars over the slope of the gradients are displayed for each molecular fit. The upper limit values are represented with triangles. The linear fit results are shown as the dark blue lines. The 1σ error bars over the slope of the gradients are displayed for each fit. In the upper right side of each subplot, the Pearson correlation coefficient, ρ, is shown.