The dectection of propanal (CH₃CH₂CHO) in Sagittarius B2(N) by means of the Green Bank Telescope was reported in 2004 by Hollis et al.. Propanal was the fourth aldehyde to be detected, following the discoveries of formaldehyde (1969), acetaldehyde (1973-1976), and propynal (1988). (The -CHO group is one of the best represented in interstellar molecules: it is also a constituent of glycolaldehyde, formamide, and newly reported cyanoformaldehyde.) Hollis et al. suggested that propanal may be formed from reactions involving propynal (HC₂CHO).

Propanal (or propyl aldehyde or propionaldehyde) is used as a feedstock for related chemicals including 1-propanol and propionic acid.