NEET 2025 · ChemistryPrevious Year Question
Among the given compounds I-III, the correct order of bond dissociation energy of the C-H bond marked with an asterisk (*) is:
- A.III > II > I
- B.II > III > I
- C.II > I > III✓
- D.I > II > III
Correct Answer
(C) II > I > III
Solution & Explanation
\textbf{Answer:} (c) \textbf{Solution:} The bond dissociation energy of a C-H bond is inversely related to the stability of the radical formed on its homolysis. The allylic/cyclopropenyl-type radical from III is the most stabilised and so has the lowest BDE; the aryl radical from I is intermediate; and the sp (alkynyl) C-H of phenylacetylene (II) gives the least-stabilised radical and so has the highest BDE. The order of radical stability is III > I > II, giving the BDE order II > I > III.
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