Quantification of Non-Covalent Interactions on the Basis of the Thermodynamic Hydrogen Bond Parameters

This paper describes how empirical free energy and/or enthalpy values for hydrogen binding strength are derived from thousands of corresponding measurements between H-bond donors and acceptors, mostly in carbon tetrachloride, and how they can be used to construct common scales or factor values (increments) also for other reactions involving electron donor and acceptor ability of functions. The corresponding databases and programs (HYBOT) allow one to predict thermodynamic values for experimentally unknown equilibria, including also ionophore complexes with crown ethers or cryptands. Applications in QSAR involve the prediction of lipophilicity from any structure on the basis of only two variables, e.g. 234 systems are described this way with a correlation coefficient r=0·96. Similarly, permeabilities and some biological properties such as narcotic activities of chemicals and anti-HIV-1 activity of some porphyrins are evaluated.