Question
Which of the following compounds will react with $$Na$$ to form 4, 5-diethyloctane?
A.
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}Br\]
B.
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}\underset{\begin{smallmatrix}
|\,\,\,\,\, \\
C{{H}_{3}}
\end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{2}}C{{H}_{2}}Br\]
C.
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}\underset{\begin{smallmatrix}
|\,\,\,\,\, \\
Br\,\,\,\,
\end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{3}}\]
D.
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}\underset{\begin{smallmatrix}
|\,\,\,\,\, \\
Br\,\,\,\,
\end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{2}}C{{H}_{3}}\]
Answer :
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}\underset{\begin{smallmatrix}
|\,\,\,\,\, \\
Br\,\,\,\,
\end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{2}}C{{H}_{3}}\]
Solution :
The reaction is Wurtz reaction and proceeds as follows :
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}-\underset{\begin{align}
& |\,\,\,\, \\
& C{{H}_{2}} \\
& |\,\,\,\, \\
& C{{H}_{3}} \\
\end{align}}{\mathop{CH}}\,-Br+2Na\,\,+\] \[Br-\underset{\begin{align}
& |\,\,\,\,\, \\
& C{{H}_{2}} \\
& |\,\,\,\,\, \\
& C{{H}_{3}} \\
\end{align}}{\mathop{CH}}\,-C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}\xrightarrow{\text{ethar}}\]
\[\underset{\text{4,5-Diethyloctane}}{\mathop{\overset{8\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}}}\,\overset{7\,\,\,\,\,\,\,}{\mathop{C{{H}_{2}}}}\,\overset{6\,\,\,\,\,\,\,}{\mathop{C{{H}_{2}}}}\,-\underset{\begin{align}
& | \\
& C{{H}_{2}} \\
& | \\
& C{{H}_{3}} \\
\end{align}}{\overset{5\,\,\,\,\,}{\mathop{CH}}}\,-\underset{\begin{align}
& | \\
& C{{H}_{2}} \\
& | \\
& C{{H}_{3}} \\
\end{align}}{\overset{4\,\,\,\,\,\,}{\mathop{CH}}}\,-\overset{3\,\,\,\,\,\,\,}{\mathop{C{{H}_{2}}}}\,\overset{2\,\,\,\,\,\,\,}{\mathop{C{{H}_{2}}}}\,\overset{1\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}}}\,}}\,\]