Density functional theory and ab-initio computational study of the 2-hydroxypyridine/2-pyridone system: a comparison with FT-IR data from matrix isolation experiments

The tautomeric equilibrium 2-hydroxypyridine <=> 2-pyridone was observed in a low-temperature Ar matrix. The infrared spectra of the tautomers were analysed and assigned using DFT/(B3-LYP and B3-PW91)/6-31++G** and RKF/6-31++G** methods. The molecular parameters (rotational constants and dipole moments) are calculated with different methods and compared with recent gas-phase microwave data. The rotational constants and dipole moments predicted using the DFT method agree much better with the experimental results than the parameters predicted at the HF level. The energy difference for the tautomeric equilibrium and the tautomerization constant were calculated and these parameters are compared with recent theoretical and experimental predictions. (C) 1999 Elsevier Science B.V. All rights reserved.