Question

The order of rate of hydrolysis of alkyl halides: $1^{\circ}, 2^{\circ}, 3^{\circ}$ and $CH_3X$ by $S_N2$ pathway is

• A. $\ce{1^{\circ} > 2^{\circ} > 3^{\circ} > CH_3X}$
• B. $\ce{CH_3X > 3^{\circ} > 2^{\circ}> 1^{\circ} }$
• C. $\ce{ CH_3X > 1^{\circ} > 2^{\circ} > 3^{\circ} }$
• D. $\ce{3^{\circ} > 2^{\circ} > 1^{\circ} > CH_3X}$

Answer 1

Answer: (C)

$\ce{ CH_3X > 1^{\circ} > 2^{\circ} > 3^{\circ} }$

Answer 2

Reactivity in $S_N2$ reactions depends upon the steric hindrance. Since the steric hindrance increases in the order: ${ CH_3X > 1^{\circ} > 2^{\circ} > 3^{\circ} }$ ?, therefore, reactivity in $S_N2$ reactions decreases in the same order, i.e., option (c) is correct.