An NMR method has been used to determine the hydrogen bond acidity, A, of a number of hydroxyisoflavones. Together with our previous studies on hydroxyflavones, these A-values enable the presence of intramolecular hydrogen bonding in hydroxyflavones and hydroxyisoflavones to be detected. A full set of Abraham descriptors has been assigned to all the monohydroxy and dihydroxy-flavones and isoflavones, and to some polyhydroxy-flavones and isoflavones as well. In these assignments, knowledge of the A-descriptor is crucial. These sets of descriptors can then be used to estimate values for a large number of physicochemical and biochemical processes.
