JEE Main20236 Apr 2023Morning ShiftChemistryHaloalkanes and HaloarenesActual
For the reaction RCH 2 Br + I - ⟶ Acetone RCH 2 I major + Br - The correct statement is
Options
- ABr – can act as competing nucleophile.
- BThe reaction can occur in acetic acid also.
- CThe transition state formed in the above reaction is less polar than the localised anion.
- DThe solvent used in the reaction solvates the ions formed in rate determining step
Correct answer
C. The transition state formed in the above reaction is less polar than the localised anion.
Step-by-step solution
R - CH 2 - Br + I - ⟶  Acetone  R - CH 2 - I + Br - As mentioned the reaction follows S N 2 reaction mechanism. The Finkelstein reaction classically involves the conversion of Alkyl bromides into Alkyl iodides by the treatment with a solution of Sodium iodide in Acetone. NaBr is not readily soluble in acetone and hence reaction shifts in forward reaction. For S N 2 reactions, transition state formed is less polar than the localised anion.