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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3g1234

Select all correct statements about the ion shown.

  1. AThe positive charge is shared by only the first, third and fifth carbons
  2. BSix pi electrons are delocalised over five carbons
  3. CThe bond between the second and third carbons has partial double-bond character
  4. DAll three contributors are equivalent

Answer: A, C

The pentadienyl cation has contributors with charge on C1, C3 and C5 (A true). It has 4 pi electrons over five carbons, so B is false. The C2-C3 bond is single in two contributors and double in one, so it has partial double-bond character (C true). The three contributors are not equivalent: the C3-charged one differs from the terminal-charged ones, so D is false.
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