Dissociation energy and associated composition changes of large molecules along reaction sequences in the UV phase (n_step = 1–70) and the post-UV phase (n_step = 71–100). The top panel is (a) the distribution of ΔD selected by the Monte Carlo simulations at each step in 10³ runs in set P1. The horizontal axis is a reaction step, and the vertical axis is ΔD in units of kJ mol⁻¹. The yellow and black lines are typical reaction sequences where 5-C sugar is formed and that without sugar formation, respectively. The middle and bottom panels show the distributions of (b) H/C and (c) O/C ratios of the molecules with four or more carbon atoms at each step in the 10³ runs. The dark colored dots indicate the results in the case allowing the formation of three- or four-membered ring structures, and light colored dots are the results where their formation is prohibited. For visual convenience, the dots with the same ΔD, H/C, and O/C at n_step are shifted slightly so that they do not overlap and clustered dots represent frequent events.