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NEET Chemistry QUESTION #1096
Question 1
Among compounds I (benzene sp\(^2\) C–H*), II (phenylacetylene sp C–H*) and III (cyclopropane C–H*), correct order of C–H bond dissociation energy:
  • III \(>\) II \(>\) I✔️
  • II \(>\) III \(<\) I
  • II \(>\) I \(>\) III
  • I \(>\) II \(>\) III
Correct Answer Explanation
Bond dissociation energy of C–H bond depends on hybridization of carbon: sp \(>\) sp\(^2\) \(>\) sp\(^3\). Compound II (alkyne/phenylacetylene): sp C–H — highest BDE. Compound III (cyclopropane): C–H has partial sp\(^2\) character due to ring strain → BDE between sp\(^2\) and sp. Compound I (benzene): sp\(^2\) C–H. Order: II \(>\) III \(>\) I. Answer: option (1) III > II > I is wrong. Correct is II > III > I = option (3).