Which of the following reactions is an example of nucleophilic substitution reaction?

1. $\mathrm{RX}+\mathrm{KOH} \longrightarrow \mathrm{ROH}+\mathrm{KX}$
2. $2 \mathrm{RX}+2 \mathrm{Na} \longrightarrow \mathrm{R}-\mathrm{R}+2 \mathrm{NaX}$
3. $\mathrm{RX}+\mathrm{H}_2 \longrightarrow \mathrm{RH}+\mathrm{HX}$
4. $\mathrm{RX}+\mathrm{Mg} \longrightarrow \mathrm{RMgX}$

Solution

Key Idea Nucleophilic substitution reactions involve substitution (replacement) of a group or atom by a nucleophile. $\begin{aligned} & \mathrm{KOH} \longrightarrow \mathrm{K}^{+}+\mathrm{OH}^{-} \\ & \mathrm{RX}+\underset{\text { nucleophile }}{\mathrm{OH}^{-}} \longrightarrow \mathrm{R}-\mathrm{OH}+\mathrm{KX} \\ & \end{aligned}$

Asked in: NEET 2009 (Screening)

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