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Homework Help: Oxidation reaction from alcohol to aldehyde

  1. Jul 5, 2009 #1
    My original question:
    Why do oxidation reactions from primary alcohols to aldehydyes/carboxylic acids, or secondary alcohols to ketones require an acid (positive hydrogen ion)? I can see that the reason we have an oxidizing agent is to take away two hydrogen ions from the alcohol, but
    why do we need an additional positive hydrogen ion?

    Someone's response:
    You need a strong electrolytic solution to facilitate the transition
    (movement) of electrons... because in order for MnO4 to be reduced
    (and cause an oxidation), it needs a source of protons as part of the

    Can someone explain WHY we need protons in order for the oxidizing agent to be reduced, and therefore oxidize the alcohol?
    If an alcohol is being oxidized to become an aldehyde, it's losing two hydrogen atoms, which are positive... why would these positive hydrogen atoms (protons) be drawn to the source of protons?
  2. jcsd
  3. Jul 5, 2009 #2


    User Avatar

    Staff: Mentor

    It has nothing to do with alcohol/aldehyde. MnO4- half reaction is

    MnO4- + 8H+ -> Mn2+ + 4H2O + 5e-

    To be an effective oxidizer it requires low pH.
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