Hydrocarbons Question 26
Question: 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]
Options:
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
Show Answer
Answer:
Correct Answer: A
Solution:
$ HI\to {H^{+}}+{I^{-}} $
$ CH_3-CH=CH_2+{H^{+}}\to $
$ \underset{\begin{smallmatrix} (\text{Minor)} \\ {1^{o}}\text{Carbonium ion} \\ \text{(Less stable)} \end{smallmatrix}}{\mathop{CH_3-CH_2-\overset{+}{\mathop{C}}H_2}}+\underset{\begin{smallmatrix} (\text{Major)} \\ {2^{o}}\text{Carbonium ion} \\ \text{(More stable)} \end{smallmatrix}}{\mathop{CH_3-\overset{+}{\mathop{CH}}-CH_3}} $
$ \underset{2^{o}Carboniumion}{\mathop{CH_3-\overset{+}{\mathop{C}}H-CH_3+{I^{-}}}}\to \underset{\begin{smallmatrix} \text{Isopropyl iodide} \\ \text{(Major product)} \end{smallmatrix}}{\mathop{CH_3-\underset{\underset{I}{\mathop{|}}}{\mathop{CH}}-CH_3}} $
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