Question

Which of the following reactions is an example of the Finkelstein reaction?

• A. C$_6$H$_5$Br + AgNO$_3$ $\rightarrow$ C$_6$H$_5$NO$_3$ + AgBr
• B. C$_6$H$_5$Br + NaI $\rightarrow$ C$_6$H$_5$I + NaBr
• C. CH$_3$Cl + KOH $\rightarrow$ CH$_3$OH + KCl
• D. C$_6$H$_5$Br + Mg $\rightarrow$ C$_6$H$_5$MgBr

Hint:

The Finkelstein reaction involves the exchange of halides, typically in polar aprotic solvents, where the halide exchange occurs between an alkyl halide and a sodium halide.

Answer 1

The Correct Option is B

The correct answer is: C₆H₅Br + NaI → C₆H₅I + NaBr.

• Finkelstein Reaction: The Finkelstein reaction is a halide exchange reaction where an alkyl halide reacts with a sodium halide in an acetone solution to replace one halogen atom with another. This is an example of a nucleophilic substitution reaction (SN2 mechanism).
• Mechanism: In this case, sodium iodide (NaI) is used to replace the bromine (Br) in C₆H₅Br, forming C₆H₅I (phenyl iodide) and sodium bromide (NaBr).
• Why Option C is correct: The reaction C₆H₅Br + NaI → C₆H₅I + NaBr is a classic example of the Finkelstein reaction, as it involves halide exchange where iodine replaces bromine in an alkyl halide.

Conclusion: Option B represents the Finkelstein reaction, where the halogen atom in the alkyl halide is substituted by another halogen atom.