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Punjab Medical Punjab - MET Solved Paper-2006

  • question_answer
    The basicity of compounds I, II, III and IV\[\underset{I}{\mathop{C{{H}_{3}}N{{H}_{2}}}}\,,\underset{II}{\mathop{{{(C{{H}_{3}})}_{2}}NH}}\,,\,\,\underset{III}{\mathop{{{(C{{H}_{3}})}_{3}}N}}\,,\]\[\underset{IV}{\mathop{{{C}_{6}}{{H}_{5}}C{{H}_{2}}N{{H}_{2}}}}\,\]varies in the order:

    A) \[I>II>III>IV\]

    B) \[II>I>III>IV\]

    C) \[III>I>II>IV\]

    D) \[IV>I>II>III\]

    Correct Answer: B

    Solution :

    Basicity of amines increases with increasing \[+I\] effect of alkyl groups.\[3{}^\circ \]amine has greater \[+I\] effect than \[2{}^\circ \] and \[1{}^\circ \] amines but less basic than these, due to steric hinderance of bulky groups. Moreover, benzyl amine is a weaker base than aliphatic amines. Hence the following compounds has the order of basicity\[\underset{I}{\mathop{C{{H}_{3}}}}\,N{{H}_{2}}(1{}^\circ ),\,\,\underset{II}{\mathop{{{(C{{H}_{3}})}_{2}}}}\,NH(2{}^\circ ),\] \[(CH\underset{III}{\mathop{_{3}{{)}_{3}}}}\,N(3{}^\circ ),\,\,{{C}_{6}}{{H}_{5}}\underset{IV}{\mathop{C{{H}_{2}}}}\,N{{H}_{2}}\]                 \[II>I>III>IV\]


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