BCECE Medical BCECE Medical Solved Papers-2004

  • question_answer
    In the following compound, least number of mono chlorination is possible :

    A)  \[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}\]

    B)  \[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{2}}-C{{H}_{3}}\]

    C)  \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-H\]

    D)  \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-C{{H}_{3}}\]

    Correct Answer: D

    Solution :

    Key Idea: Write chlorination reaction for all of them to find which gives of the, maximum number of monochlorination product. [a] \[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}+C{{l}_{2}}\xrightarrow{UV}\] \[ClC{{H}_{2}}-{{(C{{H}_{2}})}_{3}}C{{H}_{3}}+C{{H}_{3}}-\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}\,H-{{(C{{H}_{2}})}_{2}}C{{H}_{3}}\]            \[+\,C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{2}}-C{{H}_{3}}\] \[\therefore \] Total 3 monochlorinated products are formed. [b] \[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{2}}-C{{H}_{3}}+C{{l}_{2}}\xrightarrow{UV}\] \[ClC{{H}_{2}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{2}}-C{{H}_{3}}\]                 \[+\,C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}\,}}\,H-C{{H}_{2}}-C{{H}_{3}}\]                 \[+\,C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,H-C{{H}_{2}}-C{{H}_{2}}Cl\] \[\therefore \] Total 3-monochlormated products are formed. [c] \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-H+C{{l}_{2}}\xrightarrow{UV}\]                 \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-Cl+C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{2}}Cl \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-H\] \[\therefore \] Total 2- monochlorinated products are formed [d] \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-C{{H}_{3}}+C{{l}_{2}}\xrightarrow{UV}\]                  \[C{{H}_{3}}-\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{C}}\,}}\,-C{{H}_{2}}C{{l}_{2}}\] \[\therefore \] Only one monochlorinated product formed. \[\therefore \] [d] is correct answer.


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