Observed lines from Orion-KL (histogram spectra) and model (thin red curves) of ¹³C isotopes for CH₂CHCN in the ground state. The subindex in ¹³C_i (i = 1, 2, 3) corresponds to the position of the isotope in the molecule (^i₁CHCH^i₃CN). The cyan line corresponds to the model of the molecules we have already studied in this survey (see text Sect. 4.4.2), including the CH₂CHCN species. A v_LSR of 5 km s^-1 is assumed.