Notes. ^(a)d: detection, n: non-detection. ^(b)Number of detected lines (conservative estimate; see Sect. 3 of Belloche et al. 2016). One line of a given species may mean a group of transitions of that species that are blended together. ^(c)Source diameter (full width at half maximum). ^(d)Rotational temperature.^(e) Total column density of the molecule. x (y) means x × 10^y. An identical value for all listed vibrational states of a molecule means that LTE is an adequate description of the vibrational excitation. For propanal, the two conformers are considered as parts of the same species, and each column density corresponds to the total column density of the molecule. For n-butanal, the two conformers were modeled as independent species, and a conformer correction (F_conf) was applied a posteriori such that each column density corresponds to the total column density of n-butanal. For i-butanal, the gauche conformer is considered as an independent species, and its column density corresponds to the column density of this conformer only. ^(f) Correction factor that was applied to the column density to account for the contribution of vibrationally excited states in the cases where this contribution was not included in the partition function of the spectroscopic predictions. ^(g)Correction factor that was applied to the column density to account for the contribution of other conformers in the cases where this contribution could be estimated but was not included in the partition function of the spectroscopic predictions. ^(h)Linewidth (full width at half maximum). ⁽ⁱ⁾Velocity offset with respect to the assumed systemic velocity of Sgr B2(N1S), V_sys = 62 km s⁻¹. ^(j)Column density ratio, with N_ref the column density of the previous reference species marked with a *.