91Ó°ÊÓ

The $\text{β}$proton and the leaving group must be in an anti-periplanar position to undergo an elimination reaction. Antiperiplanar is the orientation where the proton is abstracted, and the leaving group removed must be in a trans position.

The $\text{β}$proton is then abstracted by a base, followed by the removal of a leaving group. Different types of $\text{β}$hydrogens give different types of elimination products.

In structure a., only one type of $\text{β}$hydrogen is present. Hence it gives only one product. But in the case of b., two different types of hydrogen are present. Hence it gives two products.

The major E2 product formed from each reactant are:

a.

Representation of the major elimination product from a

b.

Representation of the major elimination products from b