1-Bromobutane is treated with excess sodium iodide in dry acetone. Write the major organic product formed and explain the reason for its formation.
Answer
1-Iodobutane
The correct answer is 1-Iodobutane — Thus the major organic product obtained is 1-iodobutane.
Step-by-step solution
- Identify the reaction as a Finkelstein reaction, which is an SN2 substitution.
- In SN2, the nucleophile I⁻ attacks the carbon bearing the leaving group Br from the backside.
- The transition state leads to inversion of configuration and formation of C–I bond.
- NaBr, being less soluble in acetone, precipitates out, shifting the equilibrium toward product formation.
- Thus the major organic product obtained is 1-iodobutane.
Common mistake: Assuming bromide ion remains in solution and no product forms.
Concept tested: SN2 substitution (Finkelstein reaction)
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