Time evolution of the temperature and the abundances (with respect to molecular hydrogen) in the gas phase (solid lines) and on the grain surface (dashed) of HNCO, H₂NCO, NH₂CHO NCO, and CH₃NCO species during the cold-core phase and the collapse phase. The time axis is reversed to better visualise the evolution of the abundances. The observed gas-phase abundances are indicated in blue. Detections in IRAS 16293 B are from Coutens et al. (2016); Hernández-Gómez et al. (2018);? for HNCO and from Coutens et al. (2016); Jørgensen et al. (2020); ? for NH₂CHO. Detections in dense molecular clouds are from ? Marcelino et al. (2009) and Turner et al. (1999). The upper limits for the relative abundance of the gas phase H₂NCO and NCO in IRAS 16293 B are shown in red. The observed abundances for IRAS 16293 B are calculated from the observed column densities using an H₂ column density equal to 1.5 × 10²³ cm⁻² so that the chemical model reproduces the observed abundance of CH₃OH (this is equivalent to using abundances relative to CH₃OH).