Question

Which compound in the following pair will react faster in S_N2 reaction with OH⁻?

(CH₃)₃CCl or CH₃Cl

Answer 1

\[\begin{array}{cc}
\phantom{......}\ce{CH3}\\
\phantom{...}|\\
\ce{CH3 - C - Cl}\\
\phantom{...}|\\
\phantom{......}\ce{CH3}\\
\end{array}\] or CH₃, Cl

The S_N2 mechanism involves attack by the nucleophile at the carbon bearing the leaving group. But, in the case of (CH₃)₃CCl, the attack of the nucleophile at the carbon atom is hindered because of the presence of bulky substituents on that carbon atom bearing the leaving group. On the other hand, there are no bulky substituents on the carbon atom bearing the leaving group in CH₃Cl. Hence, CH₃Cl reacts faster than (CH₃)₃CCl in S_N2 reaction with OH⁻.