Overview of the chemistry along the infall trajectory (solid black curve) of the single parcel from Sect. 5.1. The solid and dashed grey lines denote the surface of the disk and the outflow wall, both at t = t_acc = 2.52    × 10⁵ yr. Physical conditions, abundances (black bars: gas; grey bars: ice) and key reactions are indicated at four points (A, B, C and D) along the trajectory. The key processes governing the overall chemistry at each point are listed in the bottom right. The type of each reaction is indicated by colour, as listed in the top left.