Question

Which of the following compounds is obtained when t-butyl bromide is treated with alcoholic ammonia?

Options

• \[\begin{array}{cc}
  \ce{CH3}\phantom{....}\\
  |\phantom{.......}\\
  \ce{CH3 - C - CH2 - NH2}\\
  |\phantom{.......}\\
  \ce{Br}\phantom{......}
  \end{array}\]

• \[\begin{array}{cc}
  \ce{CH3 - C = CH2}\\
  |\phantom{.}\\
  \phantom{..}\ce{CH3}
  \end{array}\]

• \[\begin{array}{cc}
  \phantom{...}\ce{CH3}\\
  |\\
  \ce{CH3 - C - CH3}\\
  |\\
  \phantom{...}\ce{NH2}
  \end{array}\]

• \[\begin{array}{cc}
  \phantom{...}\ce{CH3}\\
  |\\
  \ce{CH3 -  C - CH3}\\
  |\\
  \phantom{.....}\ce{NHBr}
  \end{array}\]

Answer 1

\[\begin{array}{cc}
\ce{CH3 - C = CH2}\\
|\phantom{.}\\
\phantom{..}\ce{CH3}
\end{array}\]

Explanation:

In presence of alcoholic ammonia, t-butyl bromide undergoes elimination (no substitution) to give isobutylene.

\[\begin{array}{cc}
\phantom{.}\ce{CH3}\phantom{.......................}\ce{CH3}\phantom{........}\\
\phantom{}|\phantom{...........................}|\phantom{..........}\\
\ce{CH3 - C - CH3 + \underset{{(alc.)}}{NH3} -> \underset{isobutylene}{CH3 - C = CH2} + NH4Br}\\
|\phantom{......................................}\\
\ce{\underset{{t-butyl bromide}}{Br}}\phantom{.................................}
\end{array}\]