Which of the following compounds will undergo the fastest ${\text{S}}_{\text{N}}1$ reaction?

Solution

1. The rate of ${\text{S}}_{\text{N}}1$ reaction is determined by the stability of the carbocation formed after the departure of the leaving group.
2. The carbocations formed from the given options are primary, secondary, tertiary, and primary respectively.
3. The tertiary carbocation $({\text{CH}}_3{)}_3{\text{C}}^{+}$ is the most stable due to inductive effect and hyperconjugation.
4. Hence the answer is (C).