JEE Main & Advanced Chemistry Hydrocarbons / हाइड्रोकार्बन Question Bank Alkyne

  • question_answer
    An unknown compound A has a molecular formula \[{{C}_{4}}{{H}_{6}}.\] When A is treated with an excess of \[B{{r}_{2}}\] a new substance B with formula \[{{C}_{4}}{{H}_{6}}B{{r}_{4}}\] is formed. A forms a white precipitate with ammoniacal silver nitrate solution. A may be [MP PET/PMT 1998]

    A) Butyne-1

    B) Butyne-2

    C) Butene-1

    D) Butene-2

    Correct Answer: A

    Solution :

      \[\underset{\text{1}-\text{Butyne}}{\mathop{C{{H}_{3}}-C{{H}_{2}}-C}}\,\equiv CH+2B{{r}_{2}}\to C{{H}_{3}}-C{{H}_{2}}-\underset{\underset{\,\,Br}{\mathop{|}}\,}{\overset{\overset{\,\,Br}{\mathop{|}}\,}{\mathop{C}}}\,-\underset{\underset{\,\,Br}{\mathop{|}}\,}{\overset{\overset{\,\,Br}{\mathop{|}}\,}{\mathop{C}}}\,-H\] Since the molecule takes 2 moles of \[B{{r}_{2}}\]. Therefore it is alkyne. Also it gives white ppt with Tollen?s reagent therefore acidic H is present. Hence it is 1-Butyne.


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