Limitations of the Reactivity—Selectivity Principle. Application to Free Radical Addition to Alkenes and Nucleophilic Aliphatic Substitution

Abstract

The limitations of the reactivity—selectivity principle (RSP) are discussed in terms of the qualitative configuration mixing (CM) model. It is concluded that the RSP is expected to break down for cases in which the reaction transition state takes on character largely absent in reactants or products, though not all breakdowns of the RSP are attributed to this cause. This conclusion is illustrated with two model reactions that do not follow the RSP: (a) radical addition to alkenes, and (b) nucleophilic aliphatic substitution. Analysis leads us to agree with previous statements by Jencks and Arnett that the RSP should be abandoned as a predictive tool.

Physical Organic Chemistry (POC) Makes Chemistry a Science: A Personal Reflection on POC

“…However, this was by no means the only topic to arouse stormy debate. Issues such as “reactivity selectivity”,13 the “linearity of LFER”,14 the extent to which linear free energy relationships (LFERs) provide information regarding the structure of the transition state,15 the validity of the evidence provided for the existence of the isokinetic temperature,16 and many others were also the focus of vigorous discourse. But all this was before the era of “political correctness” descended upon us.…”