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NEET levelSingle correct optionDifficulty 1 of 3o3249

The beta-chloro sulfide shown hydrolyses much faster than a primary alkyl chloride of similar size lacking the sulfur atom. What is the main reason?

  1. AA free primary carbocation is formed easily
  2. BSulfur makes chloride a better leaving group by induction
  3. CThe sulfur makes the molecule more hindered at the C-Cl carbon
  4. DNeighbouring group participation by sulfur through a cyclic sulfonium ion

Answer: D

The compound is 2-chloroethyl ethyl sulfide. The sulfur lone pair attacks the carbon bearing Cl from the back side, displacing chloride and forming a three-membered cyclic sulfonium (episulfonium) ion. This anchimeric assistance (neighbouring group participation) accelerates ionisation; water then opens the ring.
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