JEE Challenger
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Total Contributing Hyperconjugation Structures of Cyclohexyl Substituted Carbocation

The total number of contributing structures showing hyperconjugation (involving C-H bonds) for the following carbocation is

Diagram 0

Official Numerical Answer6

Step-by-Step Solution

To determine the total number of contributing hyperconjugation structures (involving C−H\text{C}-\text{H} bonds) for the given carbocation, we identify all the α\alpha-hydrogens (hydrogens attached to the sp3sp^3-hybridized carbon atoms directly adjacent to the positively charged sp2sp^2-hybridized carbocation carbon):

  1. Identification of the carbocation center:
    The central positively charged carbon (C+\text{C}^+) is bonded to three groups:

    • A methyl group (−CH3-\text{CH}_3)
    • An ethyl group (−CH2CH3-\text{CH}_2\text{CH}_3)
    • A cyclohexyl group (−C6H11-\text{C}_6\text{H}_{11})
  2. Counting the α\alpha-hydrogens (α-H\alpha\text{-H}):

    • From the methyl group (−CH3-\text{CH}_3):
      The carbon is directly attached to the carbocation center and has 33 C−H\text{C}-\text{H} bonds.
      Number of α-H=3\text{Number of }\alpha\text{-H} = 3

    • From the ethyl group (−CH2CH3-\text{CH}_2\text{CH}_3):
      Only the methylene carbon directly attached to the carbocation center contributes α\alpha-hydrogens. The terminal methyl group contains β\beta-hydrogens which do not directly participate in hyperconjugation with the carbocation.
      Number of α-H=2\text{Number of }\alpha\text{-H} = 2

    • From the cyclohexyl ring:
      The ring carbon directly bonded to the carbocation center is bonded to two adjacent ring CH2\text{CH}_2 carbons, the carbocation center, and one hydrogen atom. Thus, this α\alpha-carbon possesses 11 C−H\text{C}-\text{H} bond.
      Number of α-H=1\text{Number of }\alpha\text{-H} = 1

  3. Total number of contributing structures:
    Each α-(C−H)\alpha\text{-}(\text{C}-\text{H}) bond can participate in hyperconjugation (σC−H→p\sigma_{\text{C}-\text{H}} \to p orbital interaction, also known as no-bond resonance) to form one contributing hyperconjugation structure.

    Total number of contributing structures=3+2+1=6\text{Total number of contributing structures} = 3 + 2 + 1 = 6

Therefore, the total number of contributing structures showing hyperconjugation involving C−H\text{C}-\text{H} bonds is 6.