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: This is a halide exchange reaction where an alkyl halide reacts with a sodium halide in acetone to substitute one halogen for another, operating via an SN2 mechanism.
• Mechanism: In this specific instance, sodium iodide (NaI) substitutes the bromine (Br) in C₆H₅Br, yielding C₆H₅I (phenyl iodide) and sodium bromide (NaBr).
• Justification for Option C: The reaction C₆H₅Br + NaI → C₆H₅I + NaBr precisely illustrates the Finkelstein reaction by exchanging a bromine atom for an iodine atom within an alkyl halide.

Summary: Option B accurately depicts the Finkelstein reaction, characterized by the substitution of a halogen atom in the alkyl halide with a different halogen atom.