A) 2-methylpropene
B) but-2-ene
C) 2, 3-dimethylbut-2-ene
D) 2-methylbut-2-ene
Correct Answer: C
Solution :
| the order of hyperconjugation is \[-C{{H}_{3}}>C{{H}_{3}}C{{H}_{2}}->{{\left( C{{H}_{3}} \right)}_{2}}CH->{{\left( C{{H}_{3}} \right)}_{3}}C-\]\[\underset{\underset{\underset{\left( 2-methyl\,propene \right)}{\mathop{{{\operatorname{CH}}_{3}}}}\,}{\mathop{|}}\,}{\mathop{{{\operatorname{CH}}_{3}}-C=C{{H}_{2}}}}\,\] |
| \[\begin{align} & {{H}_{3}}C-HC=\underset{\underset{C{{H}_{3}}}{\mathop{|}}\,}{\mathop{C}}\,-C{{H}_{3}} \\ & \,\,\,\,\,\,\,\,\,\,\,\,(2-methyl\,but-2-ene) \\ \end{align}\]\[{{\operatorname{CH}}_{3}}-\underset{(but-2-ene)}{\mathop{CH=CH}}\,-C{{H}_{3}}\] \[{{\operatorname{CH}}_{3}}\underset{(2,3-dimethyl\,but-2-ene)}{\mathop{\underset{\underset{C{{H}_{3}}}{\mathop{|}}\,}{\mathop{-C}}\,=\underset{\underset{C{{H}_{3}}}{\mathop{|}}\,}{\mathop{C-}}\,C{{H}_{3}}}}\,\] \[\begin{align} & {{\operatorname{H}}_{3}}C-\operatorname{HC}=\underset{\underset{C{{H}_{3}}}{\mathop{|}}\,}{\mathop{\operatorname{C}}}\,-{{\operatorname{CH}}_{3}} \\ & \,\,\,\,\,\,\,\,\,\,\,\,(2-methyl\,but-2-ene) \\ \end{align}\] |
| Larger the number of methyl groups linked to carbon - carbon double bond, more is the hyper conjugative C - H bonds and greater is the stability of alkenes hence [c] will be more pronounced for hyper conjugation. |
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