Dewar 4-picoline produced by UV irradiation on 4-picoline in a low-temperature argon matrix was monitored by FT-IR spectroscopy. The observed infrared bands were assigned to an isomer which has a C-C bridging bond with the aid of DFT (density functional theory) calculation, where the 6-31 + + G** basis set was used to optimize the geometrical structure. No other isomer bands were observed. A. systematic comparison of the scaling factors derived from the observed and calculated wavenumbers for pyridine, 2-picoline, 4-picoline and their corresponding Dewar isomers indicates a Linear relationship between the scaling factors and the Vibrational wavenumbers.