Among the given compounds I-III, the correct order of bond dissociation energy of C-H bond marked with * is:[Image showing I: iodobenzene marked at sp2 C-H; II: vinyl benzene marked at vinyl C-H; III: cyclopropane marked at ring C-H]

Bond dissociation energy (BDE) is inversely proportional to the stability of the free radical formed after breaking the bond.II (Vinyl C-H): The radical formed on a double-bonded carbon ($s{p}^2$ hybridized) is very unstable because the electron is in an orbital with high s-character closer to the nucleus. This bond is very strong.III (Cyclopropane C-H): Due to ring strain, the C-H bonds in cyclopropane have more s-character than normal $s{p}^3$ bonds, making them stronger than typical alkanes but usually less than vinyl bonds.I (Aryl C-H): The radical formed is on the benzene ring ($s{p}^2$). While unstable, the polarization and geometry in iodobenzene often make it slightly easier to break than a simple vinyl bond.The correct order of BDE is II > III > I.