Microwave spectra of n-propanol and propanal. Assignments of α-type transitions with are shown for both molecules (K_a's are given in the figure). Top panel: Rotational spectrum of gauche-propanal with assignments from Zingsheim et al. (2022) marked in blue. Bottom panel: Assigned doublet transitions for Ag ra-propanol from Abdurakhmanov et al. (1976) are marked in red, but cannot be verified in our CP-FTMW jet experiment. Our tentative assignments of K_a = 1 transitions of Ag n-propanol are marked in blue. We note that the transition marked with an asterisk (*) is another possible candidate for a transition with K_a = 1, more information can be found in the text.