Question

What is the major product of the given $E2$ reaction?

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

The transition state of E2 consists of a H atom and a leaving group from the substrate aligned in the plane.
Thus, H and Br from anti positions should be eliminated. Rotating a carbon atom with its substitutes so as to make H and Br in antiposition (${180}^o$) and the elimination gives a cis-product where two methyl groups and ethyl groups are on same side.