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.
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawiliskiego 5a, 02-106 Warsaw, Poland. arcad@chem.uw.edu.pl
Arkadiusz
A
Ciesielski
Tadeusz M
TM
Krygowski
Michał K
MK
Cyrański
Michał A
MA
Dobrowolski
Alexandru T
AT
Balaban
D001554:Benzene / Q000737:chemistry*; D007700:Kinetics; D011083:Polycyclic Compounds / Q000737:chemistry*; D013816:Thermodynamics
D011083:Polycyclic Compounds; D001554:Benzene