Question

The order of $S_{N}1$ reactivity in aqueous acetic acid solution for the compounds
1.$H_{3}C-\stackrel{\underset{||}{O}}{C}-C{H}_2-Cl$
2. $H_{3}C-C{H}_2-C{H}_2-Cl$
3. $(H_{3}C{)}_{3}C—Cl$ is

• A. 1 > 2 > 3
• B. 1 > 3 > 2
• C. 3 > 2 > 1
• D. 3 > 1 > 2

Answer 1

Answer: (C)

The $S_{N}1$ reaction depends upon the stability of carbocations. Higher is the stability of carbocation more will be the reactivity of compounds.
The carbocation of given compounds are as follows :
$C{H}_3-\stackrel{\underset{||}{O}}{C}-C{H}_2-Cl\to C{H}_3\stackrel{\underset{||}{O}}{C}-C{H}_2^{+}+C{l}^{-}$
$C{H}_3-C{H}_2-C{H}_2-Cl\to C{H}_{3}C{H}_{2}C{H}_2^{+}+C{l}^{-}$
$(C{H}_3{)}_{3}CCl\to (C{H}_3{)}_3{C}^{+}+C{l}^{-}$
The order of stability of carbocation is

Thus, the order of reactivity of given compounds in $S_{N}1$ reaction is $3>2>1$.