Q83 / 180 · AIIMS 2007 · Chemistry

Assertion : Alkyl iodide can be prepared by treating alkyl chloride/bromide with \(\mathrm{NaI}\) in acetone. Reason : \(\mathrm{NaCl} / \mathrm{NaBr}\) are soluble in acetone while \(\mathrm{NaI}\) is not.

  • A
    If both assertion and reason are true and reason is the correct explanation of assertion.
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
  • Correct answer
    C
    If assertion is true but reason is false.
  • D
    If both assertion and reason are false.

Solution

This is Finkelstein reaction which involves the conversion of an alkyl chloride/bromide to an alkyl iodide by the addition of sodium iodide in acetone. Because sodium iodide is soluble in acetone and \(\mathrm{NaCl}\) and \(\mathrm{NaBr}\) are not, the equilibrium is shifted by the precipitation of insoluble salt. \(R-X \underset{M X}{\stackrel{M X^{\prime}}{\rightleftharpoons}} R-X^{\prime}\) The equilibrium position of the reaction depends on the nucleophilicity of the anion, whether a good leaving group is present and whether one anion is better stabilised than the other in a given solvent.

Hence, the correct answer is option: 'C'.

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