The acenes: Is there a relationship between aromatic stabilization and reactivity?

[GRAPHICS] Despite the increasing reactivity from benzene to heptacene, the acene reso nance energies per pi electron are nearly constant. The reactivities (compu ted activation energies) of the individual acene rings correlate with the r eaction energies and depend on the product stabilities. Nucleus-independent chemical shifts (NICS; note the sizes of the red dots, above) indicate tha t the more reactive inner rings actually are more aromatic than the less re active outer rings and even more aromatic than benzene itself.