Question

Which of the following(s) is/are the conditions for the E1cB reaction to occur?

• A. Substrate should have EWG at $\alpha -$ position with respect to leaving group
• B. Substrate should have hydrogen atom at $\beta -$ position with respect to leaving group
• C. Substrate should have good leaving group
• D. Substrate should have poor leaving group

Answer 1

Answer: (B), (D)

Substrate should have poor leaving group

For $E_{1}cB$ to occur, the substituted alkane must have a poor leaving group.
Strong EWG at the $\beta$ carbon with respect to the leaving group and poor leaving group favors the E1cB reaction.
It also must have a hydrogen atom on one of its beta carbon with repect to leaving group.