Question

The major products obtained when this substrate is subjected to $E_2$ reaction will be

• A.
• B.
• C. Both (A) and (B)
• D. None of these

Answer 1

The correct option is B

E2 is a bimolecular single step reaction proceeds through a transition state.
In this reaction, the base will abstract the proton and the leaving group leave the substrate which result in a partial double bond in the transition state.
The abstraction of a proton by a base and the departure of the leaving group occurs simultaneously. Hence, it is concerted reaction.
The rate of the reaction depend both on substrate and the base.
Substrate which gives more stable alkene is the reactive one.
In given compound, we have two possibility for removal of proton.
Removal of proton (1) gives a diene compound. Here, the double bond are not conjugated so they are less stable.
Removal of proton (2) gives diene compound in which the double bonds are conjugated. Thus, conjugated alkenes are more stable than normal dienes. So, (b) is the major product of the given reaction.