Question

Which of the following is an halogen exchange reaction?

• A. \(RX+\text{NaI}\rightarrow RI+\text{NaX}\)
• B. \(R-OH+HX\xrightarrow{\text{ZnCl}_{2}}R-X+\text{H}_{2}\text{O}\)
• C.

  

• D. \(>C=C\lt +HX\rightarrow >C_{{}^{|}}-C_{{}^{|}}\lt\)

Hint:

A halogen exchange replaces one halogen of an alkyl halide with another, as in the Finkelstein reaction.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
In a halogen exchange reaction one halogen atom in an alkyl halide is swapped for another halogen.

Step 2: Check option A
\(RX+\text{NaI}\rightarrow RI+\text{NaX}\) replaces X with iodine. This is the Finkelstein reaction (in dry acetone).

Step 3: Check the others
The reaction of alcohol with HX makes a halide from an alcohol. The ring reaction shown is halogenation of an aromatic ring. Addition of HX to an alkene is addition. None of these swaps one halogen for another.

Final Answer:
The Finkelstein reaction of an alkyl halide with NaI is the halogen exchange. \[ \boxed{\text{(A) }RX+\text{NaI}\rightarrow RI+\text{NaX}} \]