Exploring Mechanism of Additions to Alkenes; Extending a New Technique by Four Reactions

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

There are two proposal objectives. The first is to extend development of a technique, which has been developed by the PI, for correlating measurable characteristics in addition reactions of alkenes in order to gain information useful mechanistically and synthetically. The PI has applied the technique to enough systems to establish its viability, but its range is not determined. The technique enables (1) a procedure to determine relative magnitudes of steric and electronic effects in the rate-determining step, (2) a relatively simple way to predict the effects of substituents on reaction rates for synthetic purposes, and (3) a method to choose between alternative proposed reaction mechanisms in some cases. The simple technique to be extended is correlating (plotting) the logs of the relative rates (log krel) of the alkene addition reactions studied versus measurable characteristics of the alkenes, such as ionization potentials (IPs), their highest occupied molecular orbital energies (HOMOs), and in some cases their lowest unoccupied molecular orbital energies (LUMOs). There have been previous mechanistic studies making use of IP vs log krel comparisons, tables, and plots; this technique differs in that it focuses on the separation of steric versus electronic effects, and it requires more data points and substituents with a variety of electronic effects in the alkenes in order to spread out the data points and to facilitate visualization. Many of the reactions studied and to be studied are fundamental reactions, which appear in undergraduate organic chemistry texts. Surprisingly, the relative reactivities of many of these have not been studied at all, and in some cases, erroneous conclusions have been drawn by using too few data points or alkenes bearing substituents without a wide enough range of electronic effects. This project will advance the understanding of these fundamental reactions and benefit chemists using addition reactions in synthesis, because relative reactivity data will enable prediction of site selectivity when more than one double bond is present in the molecule, but it is desired to effect reaction at only one. The second objective is to increase the participation of native under-represented minorities (URMs) in chemistry. The direct influence of the grant will be limited due to its short (one year) duration, but subsequent funding can continue efforts toward the goals.