SIMPLE AB-INITIO MODEL FOR CALCULATING THE ABSOLUTE PROTON AFFINITY OF AROMITIES

It is shown that st simple scaled Hartree-Fock (ScHF) model describes very well the ring proton affinity (PA) of a vast variety of polysubst ituted benzenes, naphthalenes, and biphenylenes. Its utility in predic ting PAs of large alternant aromatics is illustrated on pyrene and mon ofluoropyrenes. The calculated PAs are in accordance with the availabl e experimental evidence providing at the same time useful complementar y information. Finally, it is found that PAs in polyfluoropyrenes foll ow the same simple additivity rule, based on the independent substitue nt approximation (ISA), which was observed earlier in smaller alternan t aromatic systems. The origin of the additivity property of the proto n affinity is briefly discussed.