Based on the profound influence of steric hindrance, in which of the following alkyl halides is the — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

The $S_N2$ mechanism requires the nucleophile to approach the electrophilic carbon exactly from the backside of the leaving group. Steric bulk critically impedes this approach. Therefore, $S_N2$ reactivity strictly follows the order: Methyl $> 1^\circ > 2^\circ > 3^\circ$. Among the options, 1-chlorobutane is a straight-chain $1^\circ$ halide. 1-chloro-2-methylpropane is also $1^\circ$, but the bulky branching at the adjacent $\beta$ -carbon severely slows the attack. Hence, 1-chlorobutane reacts the fastest.