Question

Among which of the following pairs of halogen compounds, the first compound undergoes faster $S_{N}2$ reaction compared to the second?

• A. $\left(a\right)$
• B. $\left(b\right)$
• C. $\left(c\right)$
• D. $\left(d\right)$

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A $\left(d\right)$
B $\left(b\right)$
C $\left(c\right)$
D $\left(a\right)$

Steric congestion around the carbon atom undergoing the inversion process will slow down the $S_{N}2$ reaction. Less congestion = faster reaction. Due to ease of backside attack first compound in option (a), (c) and (d) undergoes $S_{N}2$ faster. In case of option (b), iodide is better leaving group therefore iodobutane undergoes faster $S_{N}2$ than chlorobutane.