In the following reactions, [AIPMT (S) 2011] |
(I) \[\text{C}{{\text{H}}_{\text{3}}}-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{3}} & \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{CH}}}\,-\underset{\begin{smallmatrix} \text{ }\!\!|\!\!\text{ } \\ \text{OH} \end{smallmatrix}}{\mathop{\text{CH}}}\,-\text{C}{{\text{H}}_{\text{3}}}\xrightarrow[{}]{{{\text{H}}^{\text{+}}}\text{/Heat}}\] \[{{\left( \overset{\text{A}}{\mathop{\begin{align} & \text{major} \\ & \text{product} \\ \end{align}}}\, \right)}^{\text{+}}}\left( \overset{\text{B}}{\mathop{\begin{align} & \text{major} \\ & \text{product} \\ \end{align}}}\, \right)\] |
(ii)\[\text{A}\xrightarrow[\text{in}\,\text{absence}\,\text{of}\,\text{peroxide}]{\text{HBr,dark}}\]\[{{\left( \overset{\text{C}}{\mathop{\begin{align} & \text{major} \\ & \text{product} \\ \end{align}}}\, \right)}^{\text{+}}}\left( \overset{\text{D}}{\mathop{\begin{align} & \text{major} \\ & \text{product} \\ \end{align}}}\, \right)\] |
the major products and are respectively |
A) \[\text{C}{{\text{H}}_{\text{3}}}-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,\text{=}\,\text{CH}-\text{C}{{\text{H}}_{\text{3}}}\]and \[\text{C}{{\text{H}}_{\text{3}}}-\underset{\begin{smallmatrix} \text{ }\!\!|\!\!\text{ } \\ \text{Br} \end{smallmatrix}}{\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}}\,-\text{CH}{{ & }_{\text{2}}}-\text{C}{{\text{H}}_{\text{3}}}\]
B) \[\text{C}{{\text{H}}_{\text{3}}}-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,\text{=}\,\text{CH}-\text{C}{{\text{H}}_{\text{3}}}\]and \[\text{C}{{\text{H}}_{\text{3}}}-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\underset{\begin{smallmatrix} | \\ \text{Br} \end{smallmatrix}}{\mathop{\text{CH}}}\,-\text{C}{{\text{H}}_{\text{3}}}\]
C) \[\text{C}{{\text{H}}_{2}}=\,\,\,\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\text{C}{{\text{H}}_{2}}-\text{C}{{\text{H}}_{\text{3}}}\]and \[\text{C}{{\text{H}}_{\text{3}}}-\underset{\begin{smallmatrix} \text{ }\!\!|\!\!\text{ } \\ \text{Br} \end{smallmatrix}}{\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}}\,-\text{C}{{\text{H}}_{\text{2}}}-\text{C}{{\text{H}}_{\text{3}}}\]
D) \[\text{C}{{\text{H}}_{\text{2}}}\text{=}\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\text{C}{{\text{H}}_{\text{2}}}-\text{C}{{\text{H}}_{\text{3}}}\]and \[\underset{\begin{smallmatrix} | \\ \text{Br} \end{smallmatrix}}{\mathop{\text{C}{{\text{H}}_{\text{2}}}}}\,-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\,\text{CH}\,}}\,-\text{C}{{\text{H}}_{\text{2}}}-\text{C}{{\text{H}}_{\text{3}}}\]
Correct Answer: A
Solution :
[a] (I) \[\text{C}{{\text{H}}_{\text{3}}}-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{CH}}}\,-\underset{\begin{smallmatrix} \text{ }\!\!|\!\!\text{ } \\ \text{OH} \end{smallmatrix}}{\mathop{\text{CH}}}\,-\text{C}{{\text{H}}_{\text{3}}}\] \[\xrightarrow[{}]{{{\text{H}}^{\oplus }}\text{/ }\!\!\Delta\!\!\text{ }}\text{C}{{\text{H}}_{\text{3}}}\underset{{{\text{2}}^{\text{o}}}\,\text{carbocation}}{\mathop{-\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{CH}}}\,-\underset{\oplus }{\mathop{\text{CH}}}\,-\text{C}{{\text{H}}_{\text{3}}}}}\,\xrightarrow[\text{shift}]{\text{1,2-hydride}}\]\[\underset{\text{(more}\,\text{stable}\,{{\text{3}}^{\text{o}}}\text{carbonium}\,\text{ion)}}{\mathop{\text{C}{{\text{H}}_{\text{3}}}-\underset{\oplus }{\overset{\begin{smallmatrix} \text{C}{{\text{H}}_{\text{3}}} \\ | \end{smallmatrix}}{\mathop{\text{C}}}}\,-\text{C}{{\text{H}}_{\text{2}}}-\text{C}{{\text{H}}_{\text{3}}}}}\,\] |
\[\xrightarrow[{}]{-{{H}^{\oplus }}}C{{H}_{3}}\underset{major\,(A)}{\mathop{-\overset{\begin{smallmatrix} C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{C}}\,=CH}}\,-C{{H}_{3}}\]\[+C{{H}_{3}}\underset{mionr\,\,(B)}{\mathop{-\overset{\begin{smallmatrix} C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{C}}\,=CH}}\,=C{{H}_{2}}\] |
\[C{{H}_{3}}\underset{Major\,\,(A)}{\mathop{-\overset{\begin{smallmatrix} C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{C}}\,=CH}}\,-C{{H}_{3}}\] \[\xrightarrow[\begin{smallmatrix} in\,absence \\ of\,peroxide \end{smallmatrix}]{HBr\,(dark)}C{{H}_{3}}-\underset{Major\,(C)}{\mathop{\underset{\begin{smallmatrix} | \\ Br \end{smallmatrix}}{\overset{\begin{smallmatrix} C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{C}}}\,-}}\,C{{H}_{2}}-C{{H}_{3}}\]\[+C{{H}_{3}}-\underset{Major\,(D)}{\mathop{\underset{\begin{smallmatrix} | \\ Br \end{smallmatrix}}{\overset{\begin{smallmatrix} C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{C}}}\,-}}\,\underset{\begin{smallmatrix} | \\ Br \end{smallmatrix}}{\mathop{CH}}\,-C{{H}_{3}}\] |
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