b
(b) \(\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,C{H_3}} \\ 
  | \\ 
  {C{H_3} - C - C{H_2}} \\ 
  {|\,} \\ 
  {\,\,\,\,\,\,C{H_3}} 
\end{array} + \mathop {KOH}\limits_{(alc)}  \to \) \(\begin{array}{*{20}{c}}
  {\,\,C{H_3}\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
  {|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
  {C{H_3} - C = CH - C{H_3}} 
\end{array} + KBr + {H_2}O\)

In this reaction \({1^o}\) carbonium ion is formed which rearranges to form \({3^o}\) carbonium ion from which base obstruct proton. Hence \(2-\) methyl-\(2\) -butene is formed as a main product.

\(\mathop {\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,C{H_3}} \\ 
  | \\ 
  {C{H_3} - C - \mathop C\limits^ +  {H_2}} \\ 
  {|\,} \\ 
  {\,\,\,\,\,\,C{H_{3\,\,}}} 
\end{array}}\limits_{{1^o}\,carbonium\,less\,stable} \) \(\xrightarrow{{Methyl\,shift}}\begin{array}{*{20}{c}}
  {C{H_{3\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}}} \\ 
  {|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
  {\mathop {C{H_3} - C - C{H_2} - C{H_3}}\limits_ +  } 
\end{array}\)

 \(\xrightarrow{{Elimination{\kern 1pt} of{\kern 1pt} proton{\kern 1pt} from{\kern 1pt} \beta {\kern 1pt} carbon{\kern 1pt} which{\kern 1pt} is{\kern 1pt} less{\kern 1pt} hydrogenated}}\mathop {\begin{array}{*{20}{c}}
  {\,C{H_{3\,\,\,\,\,\,\,\,\,\,\,\,\,\,\;}}} \\ 
  {\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
  {C{H_3} - C = CH - C{H_3}} 
\end{array}}\limits_{2 - Methyl - 2 - Butene} \)