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JEE Advanced levelSingle correct optionDifficulty 3 of 3g1198

Consider the free radicals I cyclohex-2-en-1-yl, II tert-butyl, III ethyl and IV methyl. The correct order of decreasing stability is:

  1. AII > I > III > IV
  2. BI > II > III > IV
  3. CII > III > I > IV
  4. DI > III > II > IV

Answer: B

The cyclohexenyl radical is allylic, so it is resonance stabilised. tert-Butyl (9 alpha H), ethyl (3 alpha H) and methyl (0 alpha H) are stabilised by hyperconjugation only. Hence I > II > III > IV.
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