Factors Affecting the Rate of an E2 Reaction
The SN2 and E2 mechanisms differ in how the R group affects the reaction rate.
As the number of R groups on the carbon with the leaving group increases, the rate of
the E2 reaction increases.
The increase in E2 reaction rate with increasing alkyl substitution can be rationalized in
terms of transition state stability.
In the transition state, the double bond is partially formed. Thus, the transition state for
a more substituted alkene is lower in energy, reducing the activation energy for the
reaction and making the reaction faster.