Observe the given compounds I, II, and III. Identify the correct decreasing order of bond dissociation energy for the C-H bonds marked with an asterisk (*).

Step-by-step solution

The bond dissociation energy (BDE) of a C-H bond is inversely proportional to the stability of the carbon free radical formed after its homolytic cleavage. Let us analyze the radicals formed from each compound: Compound I: Homolytic cleavage of the marked C-H bond generates an allylic radical ( CH₂=CH-CH₂^ ). This radical is highly stabilized by resonance. Compound II: Cleavage of the marked C-H bond generates an sp hybridized carbon radical ( CH₃-C C^ ). The unpaired electron resides in an sp orbital with 50% s-ch