Step 1: Understanding the Concept:
Named reactions in organic chemistry are specific methods for synthesis. Halogen exchange reactions and coupling reactions have distinct reagents that serve as identifiers.
Step 2: Key Formula or Approach:
1. Finkelstein: Synthesis of alkyl iodides.
2. Swarts: Synthesis of alkyl fluorides.
3. Sandmeyer: Substitution of diazonium groups.
4. Fittig: Coupling of aryl halides.
Step 3: Detailed Explanation:
1. Finkelstein reaction: Uses NaI in dry acetone to convert alkyl chlorides/bromides to alkyl iodides. (A-III)
2. Swarts reaction: Uses metallic fluorides like SbF₃, $AgF$, or $Hg_2F_2$ to synthesize alkyl fluorides. (B-I)
3. Sandmeyer's reaction: Uses cuprous salts like Cu₂Cl₂ or $Cu_2Br_2$ to replace the diazonium group with a halogen. (C-IV)
4. Fittig reaction: Involves the coupling of two aryl halides using Sodium (Na) in dry ether. (D-II)
Step 4: Final Answer:
The correct matching is A-III, B-I, C-IV, D-II.