Question

Discuss the mechanism of unimolecular nucleophilic substitution reaction (\( S_N1 \)) in haloalkanes.

Hint:

\( S_N1 \) reactions involve carbocation formation and follow first-order kinetics: rate \( \propto [R-X] \).

Answer 1

Step 1: Definition: - The \( S_N1 \) (unimolecular nucleophilic substitution) reaction follows a two-step mechanism. - It occurs in tertiary haloalkanes due to carbocation stability. 

Step 2: Mechanism: 

Step 2.1: Formation of Carbocation (Rate Determining Step): \[ R-X \rightarrow R^+ + X^- \] 

Step 2.2: Nucleophilic Attack: \[ R^+ + Nu^- \rightarrow R-Nu \] 

Step 3: Example: \[ (CH_3)_3CBr \xrightarrow{H_2O} (CH_3)_3C^+ + Br^- \] \[ (CH_3)_3C^+ + H_2O \rightarrow (CH_3)_3COH + H^+ \]