Chemical network centered around C₂H₂ depicting the dominant formation and destruction pathways of parent molecules for the fiducial model in the surface layers (grid point 1). It includes large DIANA chemical species and uses the UMIST2012 rate coefficients. The rates are indicated on the paths. The A(B) notation represents A × 10^B. The species abundance in the surface layer in the fiducial model for a grid point is noted below the species.