Density functional theory studies on tautomeric stability and infrared spectra of 2-chloroadenine

The tautomeric stability and vibrational IR spectrum of 2-chloroadenine were studied using density functional theory (DFT) at B3LYP/6-31G* level. The amino N(9)H tautomer of 2-chloroadenine was predicted to be most stable. A scaled quantum mechanical (SQM) force field approach was used to calculate the vibrational frequencies of amino N(9)H form of 2-chloroadenine. The force constant scale factors were transferred from those of purine. The mean deviation between the predicted vibrational frequencies and the observed ones is 8.0 cm(-1). The results made it possible to give complete assignments of the IR spectrum of this molecule.