In Finkelstein reaction when acetone is replaced by water then

Options

A. Reaction occurs in forward direction via `S_(N)`1 pattway
B. Reaction occurs in forward direction via `S_(N)`2 pattway
C. Rection occurs in backward because NaCl formed in right hand side is soluble in water and cannot ppt. out
D. Reaction is not possible

Answer

### Step-by-Step Solution:

1. **Understanding the Finkelstein Reaction**:
The Finkelstein reaction involves the exchange of halogens, typically represented as:
\[ R-X + NaI \rightarrow R-I + NaX \]
where \( R-X \) is a haloalkane, \( NaI \) is sodium iodide, \( R-I \) is the product haloalkane, and \( NaX \) is the byproduct.

2. **Role of Solvent**:
In the original Finkelstein reaction, acetone is used as the solvent. One important property of acetone is that \( NaX \) (the byproduct) is insoluble in acetone. This insolubility leads to the precipitation of \( NaX \), effectively driving the reaction forward according to Le Chatelier's principle.

3. **Replacing Acetone with Water**:
When water is used instead of acetone, the solubility properties change. \( NaX \) (where \( X \) is a halogen) dissociates into \( Na^+ \) and \( X^- \) ions, which are soluble in water.

4. **Effect on Reaction Direction**:
Since \( NaX \) is soluble in water, it does not precipitate out of the solution. This means that the driving force for the forward reaction (the precipitation of \( NaX \)) is removed. Consequently, the reaction will shift in the backward direction to re-establish equilibrium.

5. **Example with Chlorine**:
If we consider \( X \) as chlorine, the reaction can be represented as:
\[ RCl + NaI \rightarrow RI + NaCl \]
Here, \( NaCl \) is also soluble in water, which reinforces that the reaction will favor the reactants (backward direction).

6. **Conclusion**:
Therefore, when acetone is replaced by water in the Finkelstein reaction, the reaction shifts in the backward direction due to the solubility of the byproduct \( NaX \) in water.

### Final Answer:
The reaction occurs in the backward direction because \( NaCl \) formed on the right-hand side is soluble in water and cannot precipitate out.

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