Summary of Reaction Control

In this tutorial, we have taken a close look at reaction control analyzing two different types of reactions. With electrophilic addition, the type of reaction control was influenced by temperature and time.

By altering the temperature and time we observed different product distributions. Generally at lower temperatures and shorter time spans equilibrium was not established and we observed kinetic control. Equilibrium cannot be established in this type of a reaction if there is not enough time. If the time is increased, we establish equilibrium and observe thermodynamic control.
With the enolate reactions, there are several different ways to influence reaction control.

Using LDA in excess, a stronger or weaker base, and a ketone in excess can all be used to control the reaction. The use of LDA in excess allows the enolate to form. Using a strong base makes it possible for the reaction to be driven to the right. The use of a weak base will enable the protons to be transferred irreversibly between the enolates and the base. Once the enolate anion is formed, it can react with the remaining ketone. Using a ketone in excess enables a second reaction to occur, where equilibrium is established.
It is important to note that reaction control is affected by different conditions for different reactions.

This project was generously supported by a grant from the Natural Science Foundation.

Pages developed by Mary A. Dewan and Dr. Abby Parrill
Department of Chemistry
Michigan State University

These pages may be downloaded and linked from other pages for academic and educational purposes. Questions, problems. and errors should be sent to parrill@cem.msu.edu.