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STD 12 - 6. Haloalkanes and Haloarenes — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 6. Haloalkanes and Haloarenes4 Marks
MCQ
Among the given pairs, in which pair first compound reacts faster than second  compound in $S_{N^1}$ reaction ?
  • A
    $CH_3 -CH_2 -CH_2 -CH_2 - Br$ or $\begin{matrix}
       C{{H}_{3}}-C{{H}_{2}}-CH-C{{H}_{3}}  \\
       \,\,\,\,\,\,\,\,\,\,|  \\
       \,\,\,\,\,\,\,\,\,\,\,\,Br  \\
    \end{matrix}$
  • ✓
    $\begin{matrix}
       C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,  \\
       |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
       C{{H}_{3}}-C-C{{H}_{2}}-C{{H}_{3}}  \\
       |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
       Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
    \end{matrix}$ or $\begin{matrix}
       \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}  \\
       \,\,\,\,\,\,\,\,\,\,|  \\
       C{{H}_{3}}-CH-CH-C{{H}_{3}}  \\
       |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
       Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
    \end{matrix}$
  • C

  • D
    $\begin{matrix}
       \,\,\,\,\,\,C{{H}_{3}}  \\
       |  \\
       C{{H}_{3}}-C-C{{H}_{3}}  \\
       |  \\
       Br  \\
    \end{matrix}$ or $\begin{matrix}
       \,\,\,\,\,\,C{{H}_{3}}  \\
       |  \\
       C{{H}_{3}}-C-C{{H}_{3}}  \\
       |  \\
       I  \\
    \end{matrix}$
✓

Answer

Correct option: B.
$\begin{matrix}
   C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,  \\
   |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   C{{H}_{3}}-C-C{{H}_{2}}-C{{H}_{3}}  \\
   |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
\end{matrix}$ or $\begin{matrix}
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}  \\
   \,\,\,\,\,\,\,\,\,\,|  \\
   C{{H}_{3}}-CH-CH-C{{H}_{3}}  \\
   |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
\end{matrix}$
b
$(b)$ In $\begin{matrix}
   C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,  \\
   |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   C{{H}_{3}}-C-C{{H}_{2}}-C{{H}_{3}}  \\
   |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
\end{matrix}$ rate of reaction is faster than $\begin{matrix}
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}  \\
   \,\,\,\,\,\,\,\,\,\,|  \\
   C{{H}_{3}}-CH-CH-C{{H}_{3}}  \\
   |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
\end{matrix}$

because in former compound stable $C^{\oplus}$ is formed

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