JEE Main & Advanced Chemistry Hydrocarbons / हाइड्रोकार्बन Question Bank Alkene

  • question_answer
    Addition of HI on the double bond of propene yields isopropyl iodide and not n-propyl iodide as the major product. This is because the addition proceeds through [CPMT 1988]

    A) A more stable carbonium ion

    B) A more stable carbanion

    C) A more stable free radical

    D) None of the above being a concerted reaction

    Correct Answer: A

    Solution :

    \[HI\to {{H}^{+}}+{{I}^{-}}\]\[C{{H}_{3}}-CH=C{{H}_{2}}+{{H}^{+}}\to \]\[\underset{\begin{smallmatrix}  (\text{Minor)} \\  {{\text{1}}^{\text{o}}}\,\text{Carbonium ion}  \\  \text{(Less stable)} \end{smallmatrix}}{\mathop{C{{H}_{3}}-C{{H}_{2}}-\overset{+}{\mathop{C}}\,{{H}_{2}}}}\,\,\,+\,\,\underset{\begin{smallmatrix}  (\text{Major)} \\  {{\text{2}}^{\text{o}}}\,\text{Carbonium ion}  \\  \text{(More stable)} \end{smallmatrix}}{\mathop{C{{H}_{3}}-\overset{+\,\,\,}{\mathop{CH}}\,-C{{H}_{3}}}}\,\] \[\underset{{{2}^{o}}\,\text{Carbonium}\,\text{ion}}{\mathop{C{{H}_{3}}-\overset{+}{\mathop{C}}\,H-C{{H}_{3}}+{{I}^{-}}}}\,\to \underset{\begin{smallmatrix}  \text{Isopropyl iodide} \\  \text{(Major product)} \end{smallmatrix}}{\mathop{C{{H}_{3}}-\underset{\underset{I}{\mathop{|}}\,}{\mathop{CH}}\,-C{{H}_{3}}}}\,\]


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