Concept: This question relates to the Finkelstein reaction, a type of halogen exchange reaction, and the solubility principles governing its effectiveness.

Why A is true but R is false:

Assertion A: Alkyl iodides can indeed be prepared by treating alkyl chlorides or bromides with sodium iodide (NaI) in acetone. This reaction is known as the Finkelstein reaction. It is a classic example of an S_N2 reaction where the halide ion (I^-) acts as a nucleophile, displacing the chloride or bromide ion. The general reaction is:
$R-X+NaI\stackrel{acetone}{\to }R-I+NaX$ (where X = Cl or Br)

Reason R: The statement that NaCl/NaBr are soluble in acetone while NaI is not, is incorrect. In fact, the Finkelstein reaction works because NaI is soluble in acetone, allowing the reaction to proceed. The key driving force for the reaction is that NaCl and NaBr are largely insoluble in acetone and precipitate out of the solution. This precipitation shifts the equilibrium of the S_N2 reaction to the right, favoring the formation of the alkyl iodide.

Option Analysis:

• A) A is true but R is false. This aligns with our analysis. Assertion A is correct (Finkelstein reaction), but Reason R incorrectly states the solubility of NaI and NaCl/NaBr in acetone.
• B) A is false but R is true. Incorrect, as A is true.
• C) Both A and R are true and R is the correct explanation of A. Incorrect, as R is false.
• D) Both A and R are true but R is NOT the correct explanation of A. Incorrect, as R is false.

Correct Answer: (A)