Question

Which of the following haloalkanes would undergo $S_{N}2$ reaction faster?

• A. I
• B. II
• C. III
• D. IV

Answer 1

Answer: (C)

Reactivity of haloalkanes in $S_{N}1$ as well as $S_{N}2$ reaction depends upon the strength of $C—X$ bond. The strength of $C—Cl$ bond is much greater as compared to $C—I$ bond or the bond length of $C—I$ bond is much greater as compared to $C—Cl$ bond Thus, $C—I$ bond breaks readily and hence is the most reactive haloalkane among given halide towards $S_{N}2$ as well as $S_{N}1$ reactions