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Mention a chemical property in which formic acid (methanoic acid) differs from acetic acid (ethanoic acid). Or Formic acid reduces Tollens' reagent but acetic acid does not. |
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Answer» Solution :Formic ACID contains a H-atom attached to a gtC=O group and hence can be regarded as an aldehyde. THEREFORE, it acts as a reducing agent and hence decolourises pink-violet colour of `KMnO_(4)` solution. Acetic acid, on the other hand, contains an alkyl (i.e., `CH_(3)`) group attached to gtC=O group. therefore, it does not acts as a reducing agent and hence does not decolourise `KMnO_(4)` solution. `underset("Formic acid")(5HCOOH)+underset("Pink-violet")(2KMnO_(4))+3H_(2)SO_(4) to 5 CO_(2)+K_(2)SO_(4) + underset("Colourless")(2MnSO_(4))+8H_(2)O` `underset("Acetic acid")(CH_(3)COOH) overset(KMnO_(4)//H_(2)SO_(4))to` No change in pink-violet colour of `KMnO_(4)` SOLN. ltrgt Similarly, methanoic acid reduces Tollens' reagent and fehling's solution but `CH_(3)COOH` does not. `underset("Formic acid")(H-overset(O)overset(||)(C)-OH)+underset("Tollens' reagent")(2[AG(NH_(3))_(2)]^(+))+2OH^(-)(Heat)to underset("Silver mirror")(2Ag darr)+4NH_(3)+CO_(2)+2H_(2)O` `underset("Formic acid")(H-overset(O)overset(||)(C)-OH)+underset("Fehling's solution")ubrace(2Cu^(2+)+4OH^(-)) overset (Heat)to underset("Red ppt.")(Cu_(2)Odarr)+CO_(2)+3H_(2)O` `underset("Acetic acid")(CH_(3)-overset(O)overset(||)(C)-OH) underset("or Fehling's solution") overset("Tollens' reagent")to`No reaction. |
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