Question

Explain why compound A does not undergo an E2 elimination with a strong base.

Short answer

The compound does not undergo an E2 reaction with a strong base because the base cannot abstract hydrogen from the $\text{β}$ carbon due to steric congestion faced by the two phenyl and chloride groups.

Step-by-step solution

Definition of E2 reaction

The single-step elimination reaction where both abstractions of a proton and removal of the leaving group take place simultaneously is known as the E2 reaction.

In this case, the rate depends on both the substrate and the base. Hence they are known as bimolecular elimination reactions.

Type of substrate present

The substrate used is sterically congested due to the presence of two bulky phenyl rings and a bulky chloride ring in the same plane. So, proton abstraction will be difficult from the $\text{β}$carbon.

They depict the E1 reaction since the carbocation obtained in the intermediate step becomes planar, and it gets easier for the base to abstract proton from the $\text{β}$carbon.

Representation of the reaction scheme