• # question_answer 63)   The intermediate carbocation formed in the reactions of $HI,\text{ }HBr$and $HCl$ with propene is the same and the bond energy of $HCl,HBr$and $HI$ is$430.5\text{ }kJmo{{l}^{-1}}$, $363.7\text{ }kJmo{{l}^{-1}}$and$296.8\text{ }kJmo{{l}^{-1}}$respectively. What will be the order of reactivity of these halogen acids?

Weaker is the bond, greater is the reactivity of halogenated acid. $\xrightarrow[\text{Decreasing}\,\text{reacticaity}]{HI>HBr>HCl}$ Since the bond dissociation energy decreases in the order: $HCl(430.5kJmo{{l}^{-1}})>HBr(363.7kJmo{{l}^{-1}})>HI(296.8kJmo{{l}^{-1}})$therefore, the reactivity of the halogen acids decreases in the reverse order : $HI>HBr>HCl$