Which of the following is halogen exchange reaction?

Options

A. `RX_NaI rarr RI+NaX`
B.
C. `R-OH+HX overset(ZnCl_2)rarr R-X+H_2O`
D. None of the above

Answer

To determine which of the given options is a halogen exchange reaction, we need to understand what a halogen exchange reaction entails. A halogen exchange reaction involves the replacement of one halogen atom with another halogen atom in a compound.

### Step-by-Step Solution:

1. **Understanding Halogen Exchange Reactions**:
- A halogen exchange reaction occurs when one halogen (X) in a compound (RX) is replaced by another halogen (Y) from another compound (e.g., RY).
- The general form of a halogen exchange reaction can be represented as:
\[ RX + Y \rightarrow RY + X \]

2. **Analyzing the Options**:
- **Option 1**: \( RX + NaI \rightarrow RI + NaX \)
- In this reaction, the halogen X in RX is replaced by I from NaI. This is a classic example of a halogen exchange reaction, known as the Finkelstein reaction.
- **Option 2**: \( RX + NaI \)
- This option does not represent a complete reaction; it only shows the reactants without any product formation. Thus, it cannot be classified as a halogen exchange reaction.
- **Option 3**: \( ROH + HX \) in the presence of \( ZnCl_2 \rightarrow RX + H_2O \)
- Here, the hydroxyl group (OH) is being replaced by the halogen (X). This is not a halogen exchange reaction because it involves the exchange of a functional group (OH) rather than one halogen for another.
- **Option 4**: None of these
- This option suggests that none of the previous options represent a halogen exchange reaction.

3. **Conclusion**:
- Based on the analysis, the only option that represents a halogen exchange reaction is **Option 1**: \( RX + NaI \rightarrow RI + NaX \).

### Final Answer:
**The correct answer is Option 1.**

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