Matching Columns for Synthesis of Benzoic Acid

To determine the correct combination for the synthesis of benzoic acid ($\text{C}_6\text{H}_5\text{COOH}$), let us evaluate each option systematically:

1. Option A: $\text{(II) (i) (S)}$

   • Column 1 $\text{(II)}$: Acetophenone ($\text{C}_6\text{H}_5\text{COCH}_3$), which contains a methyl ketone group ($-\text{COCH}_3$).
   • Column 2 $\text{(i)}$: Reagent combination $\text{NaOH} / \text{Br}_2$ (which forms sodium hypobromite, $\text{NaOBr}$).
   • Column 3 $\text{(S)}$: Haloform reaction.

   Chemical Reaction: Acetophenone reacts with sodium hydroxide and bromine to undergo the haloform (bromoform) reaction: $\text{C}_6\text{H}_5\text{COCH}_3 + 3\text{Br}_2 + 4\text{NaOH} \rightarrow \text{C}_6\text{H}_5\text{COONa} + \text{CHBr}_3 + 3\text{NaBr} + 3\text{H}_2\text{O}$

   Subsequent acidification converts sodium benzoate ($\text{C}_6\text{H}_5\text{COONa}$) into benzoic acid ($\text{C}_6\text{H}_5\text{COOH}$). Thus, this combination correctly yields benzoic acid via haloform reaction.

2. Option B: $\text{(IV) (ii) (P)}$

   • Phenol ($\text{IV}$) with $\text{Br}_2/h\nu$ ($\text{ii}$) does not lead to benzoic acid or a condensation reaction ($\text{P}$).

3. Option C: $\text{(I) (iv) (Q)}$

   • Toluene ($\text{I}$) does not undergo Kolbe's carboxylation ($\text{Q}$) with $\text{NaOH}/\text{CO}_2$ ($\text{iv}$) to yield benzoic acid (Kolbe's carboxylation is characteristic of phenol to produce salicylic acid).

4. Option D: $\text{(III) (iv) (R)}$

   • Benzaldehyde ($\text{III}$) with $\text{NaOH}/\text{CO}_2$ ($\text{iv}$) does not undergo a substitution reaction ($\text{R}$) to synthesize benzoic acid.

Hence, the only correct combination is (II) (i) (S).

Correct Option: A