On prediction of OH stretching frequencies in intramolecularly hydrogen bonded systems

OH stretching frequencies are investigated for a series of non-tautomerizing systems with intramolecular hydrogen bonds. Effective OH stretching wavenumbers are predicted by the application of empirical correlation procedures based on the results of B3LYP/6-31G(d) theoretical calculations in the harmonic and PT2 anharmonic approximations, as well as on experimental NMR parameters, i.e., proton chemical shifts (delta(H)) and two-bond deuterium isotope effects on C-13 chemical shifts ((2)Delta C-OD). The procedures are applied in a discussion of the spectra of 2,6-dihydroxy-4-methylbenzaldehyde and 8-hydroxyquinoline N-oxide. The spectrum of the former displays a broad, composite band between 3500 and 2500 cm(-1) which can be assigned to overlapping monomer and dimer contributions. In the latter case, the results support a reassignment of the OH stretching band of 8-hydroxyquinoline N-oxide: the reassignment is supported by correlation with the IR spectra of a series of substituted derivatives. (C) 2012 Elsevier B.V. All rights reserved.