Observed lines of CH₂CHCN in the 31−50 GHz frequency range toward TMC-1. The abscissa corresponds to the rest frequency assuming a local standard of rest velocity of 5.83 km s⁻¹. The ordinate is the antenna temperature, corrected for atmospheric and telescope losses, in mK. The violet line shows the synthetic spectrum obtained using the parameters derived from a rotational diagram of the observed lines (T_r = 4.5 ± 0.3 K and N(CH₂CHCN) = (6.5 ± 0.5) × 10¹² cm⁻²). Numbers in the upper left corners of the panels indicate the multiplicative factor applied to the synthetic spectrum to match the data. The rotational quantum numbers are provided in the upper right corners of each panel. The hyperfine structure of each rotational transition has been taken into account in the calculation of the synthetic spectra. Line parameters are given in Table A.1.