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Chemistry Question 65 – JEE-MAIN 2025

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Given below are two statements: Statement I : Hyperconjugation is not a permanent effect. Statement II : In general, greater the number of alkyl groups attached to a positively charged C-atom, greater is the hyperconjugation interaction and stabilization of the cation. In the light of the above statements, choose the correct answer from the options given below

Consider whether hyperconjugation is a temporary or permanent electronic effect in organic molecules.

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Ninja Strategy•Evaluate Each Statement Independently

Determine the truth value of each statement separately based on fundamental organic chemistry principles, then combine the results to find the correct option.

Step 1: Analyze Statement I: Nature of Hyperconjugation✦ Active

Hyperconjugation is a permanent electronic effect involving the delocalization of σ electrons of C-H bonds. It is always present in molecules where the structural requirements are met. Therefore, the statement "Hyperconjugation is not a permanent effect" is false.

Step 2: Analyze Statement II: Hyperconjugation and Carbocation Stability○ Expand

The stability of carbocations increases with the number of alkyl groups attached to the positively charged carbon atom. This is because alkyl groups provide α-hydrogens, which participate in hyperconjugation, leading to greater delocalization of charge and increased stabilization. For example, tertiary carbocations are more stable than secondary, which are more stable than primary, due to more α-hydrogens and thus more hyperconjugative structures. Therefore, the statement "In general, greater the number of alkyl groups attached to a positively charged C-atom, greater is the hyperconjugation interaction and stabilization of the cation" is true.

Step 3: Conclusion○ Expand

Based on the analysis, Statement I is false, and Statement II is true. This corresponds to option 4.

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