BHU PMT BHU PMT (Screening) Solved Paper-2005

  • question_answer
    Which of the following will show geometrical isomerism?

    A)  But-1-ene

    B)  But-2-ene

    C)   2, 3-dichlorobutane

    D)  Ethene

    Correct Answer: B

    Solution :

                     Key Idea: For a compound to exhibit geometrical isomerism it must have following two things (i) It should have at least one carbon-carbon double bond. (ii) The two groups attached to same carbon atom should be different. Now draw all the choices to find answer  \[\underset{But-1-ene}{\mathop{{{H}_{2}}C=C{{H}_{2}}}}\,C{{H}_{2}}C{{H}_{3}}\] (No geometrical isomerism because two groups attached to carbon atom are same)  \[\underset{But-2-ene}{\mathop{{{H}_{3}}CCH=CHC{{H}_{3}}}}\,\] It will show geometrical isomerism as it full fills both conditions.  \[\underset{2,\text{ }3-dichlorobutane}{\mathop{{{H}_{3}}C\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\mathop{CH}}\,=\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\mathop{CH}}\,C{{H}_{3}}}}\,\] (No geometrical isomerism as it does not complete any condition.)  Ethene \[{{H}_{2}}C=C{{H}_{2}}\] No geometrical isomerism as group attached to carbon atoms are same.


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