Spectral Properties Of Pyridine

1. The infrared spectrum (IR) of pyridine: The infrared spectrum of aromatic heterocyclic compounds is similar to that of benzene compounds, with C-H stretching vibration at 3070-3020cm-1, aromatic ring stretching vibration (skeleton band) at 1600-1500cm-1, and out of plane bending vibration of aromatic hydrogen at 900-700cm-1.
2. Nuclear Magnetic Resonance Hydrogen Spectroscopy (HNMR) of Pyridine: Hydrogen Nuclear Chemical Shift of Pyridine and Benzene Ring Hydrogen( δ Compared to being in a low field, the chemical shift is greater than 7.27, and the absorption peak of hydrogen on the carbon adjacent to the heteroatom is more inclined towards the low field. When there are electron donating groups attached to the heterocyclic ring, the chemical shift shifts towards a higher field, while when the substituent is electrowithdrawing, the chemical shift shifts towards a lower field.
3. UV absorption spectrum of pyridine: Pyridine has two UV absorption bands, one at 240-260nm( ε= 2000) corresponds to the π → π * transition (similar to benzene). Another line in the 270nm region corresponds to n → π * transition( ε= 450).