J & K CET Medical J & K - CET Medical Solved Paper-2010

  • question_answer
    Which of the following is the correct increasing order of basicity of amines in gaseous phase?

    A) \[{{(CH{{  }_{3}})}_{2}}NH>C{{H}_{3}}N{{H}_{2}}>{{(C{{H}_{3}})}_{3}}N>N{{H}_{3}}\]

    B) \[{{(C{{H}_{3}})}_{3}}N>{{(C{{H}_{3}})}_{2}}NH>C{{H}_{3}}N{{H}_{2}}>N{{H}_{3}}\]

    C) \[{{(C{{H}_{3}})}_{2}}NH>{{(C{{H}_{3}})}_{3}}N>C{{H}_{3}}N{{H}_{2}}>N{{H}_{3}}\]

    D)  \[{{(C{{H}_{3}})}_{3}}N>C{{H}_{3}}N{{H}_{2}}>{{(C{{H}_{3}})}_{2}}NH>N{{H}_{3}}\]

    Correct Answer: B

    Solution :

                    Basicity of amines depends upon the availability of lone pair of electrons of nitrogen for donation.\[-C{{H}_{3}}\]group, being electron donating, increases the electron density over nitrogen and thus, the lone pair of nitrogen is more available for donation. As the number of\[C{{H}_{3}}\]group increases, basicity increases. Thus, the order of basicity of given amines(in gaseous phase) is  \[{{(C{{H}_{3}})}_{3}}N>{{(C{{H}_{3}})}_{2}}NH>C{{H}_{3}}N{{H}_{2}}>N{{H}_{3}}\] \[{{3}^{o}}\]amines has less basicity due to steric hindrance in aqueous solution.


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