Abstract
Recent interest in quantitative aromaticity indices has focussed on structural, magnetic, and energetic criteria. In this work, aromaticity indices based on polarizabilities are compared with indices based upon bond orders for benzene and 12 azines, pyrrole and 9 azoles, furan and 9 oxazoles, and thiophene and 8 thiazoles. The best polarizability-based index of aromaticity we find is the polarizability anisotropy of the π-electrons. However, none of the indices constructed from polarizabilities seem to be entirely suitable as measures of aromaticity. The comparison of the structural and polarizability scales enables us to formulate three critical tests that can be used to eliminate quickly unsuitable aromaticity scales for this set of heterocycles.