Calculated fractional abundance of cyano propargyl radicals (C₄H₂N, where all possible isomers are included) as a function of time. The solid blue line corresponds to the standard UMIST 2022 case, in which reactions of C₄H₂N with neutral atoms are not included, while the dashed blue line corresponds to the case in which C₄H₂N radicals react fast with neutral C, N, and O atoms. The horizontal dotted lines correspond to the observed abundances of the two cyano propargyl isomers detected in TMC-1, CH₂C₃N, and HCCCHCN, adopting a column density of H₂ of 10²² cm⁻² (Cernicharo & Guélin 1987).