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WB JEE Medical WB JEE Medical Solved Paper-2012

  • question_answer
    Among the following carbocations: \[P{{h}_{2}}{{C}^{+}}C{{H}_{2}}Me\,\,(I),\]\[PhC{{H}_{2}}C{{H}_{2}}C{{H}^{+}}Ph\,(II),\]\[P{{h}_{2}}CHC{{H}^{+}}Me\,\,(III)\]and \[P{{h}_{2}}C(Me)C{{H}_{2}}\]\[\,(IV),\]the order of stability is

    A)  IV > II > I > III   

    B)  I > II > III > IV

    C)  II > I > IV > III   

    D)  I > IV > III > II

    Correct Answer: B

    Solution :

     The order of stability of carbocation is \[{{3}^{o}}\] benzylic \[>{{2}^{o}}\] benzylic \[>{{2}^{o}}>{{1}^{o}}.\] Thus, the correct order of stability will be \[Ph-\underset{I}{\overset{Ph}{\mathop{\underset{+}{\overset{|}{\mathop{C}}}\,}}}\,-C{{H}_{2}}C{{H}_{3}}>PhC{{H}_{2}}C{{H}_{2}}-\underset{(II)}{\overset{H}{\mathop{\underset{+}{\overset{|}{\mathop{C}}}\,}}}\,-Ph\]\[>P{{h}_{2}}CH-\underset{(III)}{\mathop{\underset{Me}{\overset{H}{\mathop{\underset{|}{\overset{|}{\mathop{C}}}\,}}}\,}}\,+>Ph-\underset{(IV)}{\mathop{\underset{Ph}{\overset{Me}{\mathop{\underset{|}{\overset{|}{\mathop{C}}}\,}}}\,}}\,-\underset{+}{\mathop{C}}\,{{H}_{2}}\]


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