A test is made of the concept of "isoresonance", wherein two species are so related if each have like numbers of the same (type of) bonds and there is a suitable isomorphism between superpositions of pairs of Kekul structures. The test is primarily via computations using a few different semiempirical quantum-chemical models on 48 benzenoid structures with over 30 (sometimes overlapping) different isoresonant pairs. Some test is made comparing other experimental data. There is observed to be a high correlation between resonance energies (or certain other properties) of isoresonant pairs - indeed more so than correspondences predicted by some other previously proposed classifications.
