Question

Which of the following undergoes nucleophilic substitution exclusively by $S_{N}1$ mechanism?

• A. Ethyl chloride
• B. Isopropyl chloride
• C. Tert-butyl chloride
• D. Chlorobenzene

Answer 1

The correct option is C Tert-butyl chloride

In $S_{N}1$ reaction mechanism, formation of carbocation is the rate determining step.
Thus,
$\text{Rate of}{S}_{N}1\text{reaction}\propto \text{Stability of carbocation}\text{Carbocation stability order:}{3}^o>2^o>1^o>\text{Methyl}$

Carbocation formed from tertiary butyl chloride will be the most stable out of the given options as that carbocation is tertiary. Therefore, correct option is (c).