Proton-acceptor ability of substituted pyridine N-oxides

The dipole moments and molar Kerr constants of H-bonded complexes of pyridi ne N-oxides with phenols were examined. Comparison of the dipole moments an d molar Kerr constants of the complexes, obtained experi- mentally and calc ulated by additive schemes and by AMI and PM3 semiempirical methods, shows that the quantum-chemical methods used adequately describe the electrical p roperties of the complexes. It is shown that the logarithm of the equilibri um constants of complex formation fairly correlate with the charge on the o xygen atom of the N-O group of pyridine N-oxides. A method for estimation o f the equilbrium constants of the first and second stages of complex format ion was proposed. It is found that the polarity of the hydrogen bond correl ates with the total charge on the H atom of the electron donor and the O at om of the proton acceptor.