E2 Reactions

E2 reactions are elimination reactions that occur via a one-step mechanism. In this reaction, a leaving group is eliminated from an organic substrate, and a new pi bond is formed. E2 reactions are characterized by the following features:

Bimolecular Reaction

The E2 reaction is a bimolecular reaction, which means that the rate of the reaction depends on the concentration of both the substrate and the base. The reaction rate is proportional to the concentration of both the substrate and the base.

Reactivity Order RI RBr RCl

The reactivity order of the E2 reaction follows the order of the halides in terms of their leaving group ability. The order of reactivity is RI> RBr> RCl. This is because the strength of the carbon-halogen bond decreases as we move down the halogen group. As a result, the leaving group ability of the halides increases as we move down the group.

Reactivity Order of RX is 30 20 10

The reactivity of the E2 reaction also depends on the nature of the substrate. The reactivity order of the substrates follows the order RX: R3C-X> R2CH-X> RCH2-X> CH3-X. This means that tertiary substrates are more reactive than secondary substrates, which are more reactive than primary substrates, which are more reactive than methyl substrates.

Rearrangement Occurs

In the E2 reaction, rearrangement does not occur. The reaction proceeds via a one-step mechanism, and the stereochemistry of the substrate is preserved. However, in some cases, rearrangement may occur if the substrate is prone to rearrangements, such as in the case of allylic or benzylic substrates.

Conclusion

In conclusion, the E2 reaction is a bimolecular elimination reaction that follows a one-step mechanism. The reactivity of the reaction depends on the leaving group ability of the halides and the nature of the substrate. The E2 reaction does not involve rearrangement of the substrate.