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NEET Chemistry NEET PYQ-Aldehydes Ketones

  • question_answer
    \[\text{C}{{\text{H}}_{\text{3}}}\text{CHO}\]and \[{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\text{C}{{\text{H}}_{\text{2}}}\text{CHO}\] can be distinguished chemically by    [AIPMT (S) 2012]

    A) Benedict test     

    B) Iodofrom test

    C) Tollen's reagent test        

    D) Fehling solution test

    Correct Answer: B

    Solution :

    [b] \[C{{H}_{3}}CHO\] and \[{{C}_{6}}{{H}_{5}}C{{H}_{2}}CHO\]both being aliphatic aldehydes react with Tollen's reagent, Fehling solution and Benedict solution. So, these reagents cannot be used to distinguish them. \[C{{H}_{3}}CHO\] reacts with NaOH and 12 to give yellow crystals' of iodoform while \[{{C}_{6}}{{H}_{5}}C{{H}_{2}}CHO\] does not react with it.                               
    \[C{{H}_{3}}CHO+3{{I}_{2}}+4NaOH\xrightarrow[{}]{{}}CH{{I}_{3}}\]\[+HCOONa+3NaI+3{{H}_{2}}O\]
    \[{{C}_{6}}{{H}_{5}}C{{H}_{2}}CHO+{{I}_{2}}+NaOH\xrightarrow[{}]{{}}No\]reaction
    Thus,\[C{{H}_{3}}CHO\]and\[{{C}_{6}}{{H}_{5}}C{{H}_{2}}CHO\]can be distinguished by iodoform test.


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