Question

Which of the following reactions are both stereospecific and stereoselective?

• A. $S_{N}1$
• B. $S_{N}2$
• C. $E_1$
• D. $E_2$

Answer 1

Answer: (B), (D)

The correct options are
B $S_{N}2$
D $E_2$

$S_{N}2$ and $E_2$ are both stereospecific because the attack from the back by ${Nu}^{\stackrel{\cdot \cdot }{\ominus }}$ in $S_{N}2$ and attack by base $E_2$ (at $\beta$-H atom) are specific. Both of them form exclusively only one product.