For the reaction:

image 77

The correct statement is :
(1) The transition state formed in the above reaction is less polar than the localised anion.
(2) The reaction can occur in acetic acid also.
(3) The solvent used in the reaction solvates the ions formed in rate determining step.
(4) Br– can act as competing nucleophile.

Answer: Option 1
Solution:

The correct statement is :(1) The transition state formed in the above reaction is less polar than the localised anion.

Option 1: This statement is correct. In the Finkelstein reaction, the reaction mechanism involves a nucleophilic substitution where the iodide ion (I-) replaces the halide ion (Cl- or Br-) in the alkyl halide. The transition state of the reaction is typically characterized by a partial bond formation between the nucleophile (I-) and the carbon atom of the alkyl halide. This transition state is indeed less polar than the localized anion (I-) because it represents a partial bond formation, which is less polar than the complete ion.
Option 2: The Finkelstein reaction is typically carried out in polar aprotic solvents like acetone or dimethyl sulfoxide (DMSO), which are more suitable for this kind of nucleophilic substitution reaction. It’s less likely to occur in acetic acid because acetic acid is a polar protic solvent, which can potentially hinder the reaction by solvating the ions formed in the rate-determining step. Hence, Option 2 is incorrect.
Option 3: This statement is more generally true for polar solvents But In the case of Finkelstein reactions, polar aprotic solvents are used. Hence this is a incorrect statement.
Option 4: In the Finkelstein reaction, the goal is to replace the existing halide (Cl- or Br-) with iodide (I-), and in general, Bromide ions have more charge density than Iodide ions because of their small size. Hence Polar Aproptic solvent used in Reaction repel this Bromide Ion and ultimately NaBr precipitate gets formed.

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