Synthetic popularity reflects chemical reactivity

Large and diverse databases of chemical reactions contain statistically significant information about the propensities of molecules to undergo specific chemical transformations. It is shown that this information can be quantified to reflect reaction thermodynamics/kinetics and can be used to construct primitive (yet accurate) reactivity indices from the counts of reported reactions involving molecules/molecular positions of interest. These indices correlate with frontier orbital (FO) populations or Hammett sigma and rho parameters for a range of reactions involving aromatic substrates. These findings suggest that large chemical databases are not only a historical repository of chemical knowledge but also tools with which one can make useful chemical predictions. Copyright (C) 2009 John Wiley & Sons, Ltd.