ABSTRACT
This chapter examines the problem of aromaticity in a large number of papers on magnetochemistry dealing with the effects of the mutual influence of atoms in organic molecules. Aromaticity is a vulnerable but valuable concept that has proved difficult to define and to express quantitatively. Among the various experimental indices of aromaticity, the criteria based on the magnetic susceptibility obviously have the strongest physical foundation, since the magnetic susceptibility tensor is a function of the degree of delocalization of the p-electrons in cyclic system. Modern magnetochemical studies of aromaticity have been based on the assumption that any interaction can be described quantitatively by the deviation from additivity of those properties in which this interaction is revealed. A study of the magnetooptical properties of a series of aromatic hydrocarbons and their corresponding quinone derivatives showed that the aromatic hydrocarbons have a higher magnetic susceptibility than their quinones.
