Temporal variations of molecular abundances (top) and abundance ratios (bottom) in the static phase (left) and during the collapse (right) in model MC2B in the fluid parcel, which reaches R = 5 AU at the final time of the simulation. Before the collapse begins, the temperature is 10 K and the number density of hydrogen nuclei (n_H) is 2.3 × 10⁴ cm^-3. The horizontal axis of the right panels is set to be t_final−t, where t_final represents the final time of the simulation and t = 0 corresponds to the onset of the collapse. The solid lines, the dashed lines, and the dotted lines represent molecules in the bulk ice mantle, molecules in the surface ice layers, and gaseous molecules, respectively.