engleski

Additivity of the Proton Affinity of Polysubstituted Benzenes: The Ipso Position

It is shown, by the MP2(fc)/6-31G**//HF/6-31G* + ZPE(HF/6-31G*) theoretical mo ; del and concomitant use of homodesmic reactions, that the ipso proton affinities in polyfluorinated benzenes follow a simple additivity rule. Performance of the latter is good, as evidenced by a law average absolute deviation Delta(abs) approximate to 0.8 kcal/mol from the accurate ab initio results, Additional evidence supporting the additivity concept is provided by good accordance with the experimental proton affinity (PA) for perfluorobenzene. The present approach enables estimates of the ipso PAs of multiply substituted aromatics. It is particularly useful in those systems which involve atoms or atomic groupings with lone pairs of electrons proximate to the aromatic pi moiety. The additivity rule of thumb offers a simple rationalization of the ipso proton affinities. The origin of the PA additivity is briefly discussed.

zero-point energies ; substituted benzenes

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