Radial abundance profiles of the main C- and O-bearing volatile molecules in the gas phase (dotted lines) and in the ice phase (solid lines) in the disc midplane after 3 Myr of evolution with the time-dependent model (full model). The results are shown for the four chemical scenarios and the three investigated grain sizes assuming α = 10^-3. The horizontal small arrows indicate the initial abundances of H₂O, CO, CO₂, CH₃OH, and CH₄ in the gas phase in the inheritance scenario (see also Table 2). Note that CO and CO₂ have the same initial abundance. The black profile (CRC), represents the cumulative abundance of additional carbon-rich compounds, including carbon chains, hydrocarbons, nitriles, and other complex organics.