The proposed structures of the dimeric products obtained from aliphatic aldehydes and arylamines were reexamined by IR and NMR spectra. The 1, 2, 3, 4-tetrahydroquinoline structure was ascertained in the case of acetaldehyde or propionaldehyde, and aldolic structure was confirmed in the case of n-butyraldehyde. It was observed that the latter readily isomerizes to the former type in the presence of acetic acid. Conformational analysis of a ...