Are thermodynamic and kinetic stabilities correlated? A topological index of reactivity toward electrophiles used as a criterion of aromaticity of polycyclic benzenoid hydrocarbons.
A topological index of reactivity (TIR) of benzenoid hydrocarbons is defined basing on an approximate value of the bicentric localization energies. TIR values correlate with all known (24) Hammett-Streitwieser position constants, based on kinetic data for electrophilic substitution in benzenoid hydrocarbons. The maximum value of the index, denoted by TIR(max), defines the stability of a molecule toward electrophiles. For all 35 nonisoarithmic molecules of benzenoid hydrocarbons for which Hess and Schaad data are known, TIR(max) values correlate with classical numerical characteristics of aromaticity: resonance energy per pi-electron (REPE), HOMO-LUMO gap, and geometry based aromaticity index HOMA. Correlation between TIR(max) and exaltation of magnetic susceptibility is also found for cata-condensed benzenoid hydrocarbons, whereas if the peri-condensed ones are included, no correlation is observed. This can be ascribed to the presence of both paratropic and diatropic rings in perifusenes.
Ciesielski
Arkadiusz
A
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawiliskiego 5a, 02-106 Warsaw, Poland. arcad@chem.uw.edu.pl
Krygowski
Tadeusz M
TM
Cyrański
Michał K
MK
Dobrowolski
Michał A
MA
Balaban
Alexandru T
AT
D001554:Benzene / Q000737:chemistry*; D007700:Kinetics; D011083:Polycyclic Compounds / Q000737:chemistry*; D013816:Thermodynamics
D011083:Polycyclic Compounds; D001554:Benzene