Vibrational spectra, structure, and theoretical calculations of 2-fluoro- and 3-fluoropyridine

The infrared and Raman spectra of liquid and vapor-phase 2-fluoropyridine and 3-fluoropyridine have been recorded and assigned. Ab initio and DFT calculations were carried out to compute the molecular structures and to verify the vibrational assignments. The observed and calculated spectra agree extremely well. The ring bond distances of the fluoropyridines are very similar to those of pyridine except for a shortening of the C–N(F) bond in 2-fluoropyridine. The C–F bond stretching frequencies are similar to that in fluorobenzene reflecting the influence of the ring π bonding.

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► The structures of 2-fluoropyridine and 3-fluoropyridine were calculated.
► The infrared and Raman spectra of the fluoropyridines were recorded and assigned.
► DFT calculations do an excellent job of predicting the observed spectra.
► The fluoropyridine ring bond distances are similar to those in pyridine.
► The fluoropyridine ring vibrational frequencies are similar to those in pyridine.