13. HYDROCARBONS (HM)
Explanation:
\(CH _2= CH - CH = CH _2+ HBr \longrightarrow \underset{1,2 -addition \,product}{\begin{matrix} C{{H}_{3}}-CH-CH=C{{H}_{2}}+ \\ |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\ Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\ \end{matrix}} \underset{1,4-addition\, product}{\begin{matrix} C{{H}_{3}}-CH=CH-C{{H}_{2}} \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,| \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,Br \\ \end{matrix}}\)
Under mild conditions (temprature \(=-80^{\circ} C\) ), kinetic product is the \(1,2-\) addition product and under vigorous conditions, (temp. \(=40^{\circ} C\) ) thermodynamic product is the \(1,4\) -addition product.
Hence, \(1\)-bromo -\(2\)-butene is the major product under a given condition.