Chemical Reactivity Project

Is there some way to predict how two molecules will react given their atom structures without doing an multiple transition state search? As it turns out, there is a growing body of work that is often termed "Chemical Reactivity Index Theory" that deals with just this question. The idea is to obtain electronic properties of isolated molecules, then use those properties to predict how the molecules will react.

A Propyl Cation Approaching Toluene

Take the reaction of toluene with a propyl cation, for example. Where will the propyl group add on to the aromatic ring? Conceptually the answer to this question could be divided into two parts. First, what sort of chemical reaction is likely to occur if two molecules encounter each other in a certain "configuration". Secondly, what sort of encounters are likely to happen?