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    Hey everyone!

    So, ethanol is oxidized twice after dichromate ion solution is introduced

    CH3CH2OH + [O] --> CH3COH + H2O

    and after that

    CH3COH + [O] --> CH3COOH

    So, the question is, how would I stop (or limit) the oxidation process after the first oxidation?
    Is the temperature crucial? (As far as I know, you need to cool it down to 20ºC, am I right?)

    Thank you everyone!
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    (Original post by ioffer007)
    Hey everyone!

    So, ethanol is oxidized twice after dichromate ion solution is introduced

    CH3CH2OH + [O] --> CH3COH + H2O

    and after that

    CH3COH + [O] --> CH3COOH

    So, the question is, how would I stop (or limit) the oxidation process after the first oxidation?
    Is the temperature crucial? (As far as I know, you need to cool it down to 20ºC, am I right?)

    Thank you everyone!
    In practice, you can't very easily. But I think A level specs teach differently... Not sure what they say though.
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    The boiling point of the aldehyde is lower than the carboxylic acid, so it's possible to distil out the aldehyde before further oxidation occurs.
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    AQA book, Unit 2, Chapter 16 discusses this topic


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    (Original post by ioffer007)
    Hey everyone!

    So, ethanol is oxidized twice after dichromate ion solution is introduced

    CH3CH2OH + [O] --> CH3COH + H2O

    and after that

    CH3COH + [O] --> CH3COOH

    So, the question is, how would I stop (or limit) the oxidation process after the first oxidation?
    Is the temperature crucial? (As far as I know, you need to cool it down to 20ºC, am I right?)

    Thank you everyone!
    I was taught using dilute H2SO4 and dilute dichromate without reflux would only oxidise it to aldehyde.
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    (Original post by ioffer007)
    Hey everyone!

    So, ethanol is oxidized twice after dichromate ion solution is introduced

    CH3CH2OH + [O] --> CH3COH + H2O

    and after that

    CH3COH + [O] --> CH3COOH

    So, the question is, how would I stop (or limit) the oxidation process after the first oxidation?
    Is the temperature crucial? (As far as I know, you need to cool it down to 20ºC, am I right?)

    Thank you everyone!
    If you have the Nelson Thornes chemistry textbook, it's explained on page 217 at the top. If not I'll try and summarise. They distil it by reducing the temperature of the condenser and is put in the distillation position (rather than reflux) as shown below:
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    So as soon as the aldehyde (ethanal) is formed it vaporises and then distils off to stop it from being further oxidised.
    Hope this helped!
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    (Original post by Secret.)
    So as soon as the aldehyde (ethanal) is formed it vaporises and then distils off to stop it from being further oxidised
    So, what is being distilled off is aldehyde and not the ethanoic acid?
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    (Original post by ioffer007)
    So, what is being distilled off is aldehyde and not the ethanoic acid?
    yes thats right, if you leave it to oxidise further, then you get ethanoic acid
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    (Original post by Hormonal)
    I was taught using dilute H2SO4 and dilute dichromate without reflux would only oxidise it to aldehyde.

    Isn't it if you have an excess of ethanol, then it would be further oxidized?
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    (Original post by Libby18)
    yes thats right, if you leave it to oxidise further, then you get ethanoic acid
    But ethanoic acid will never be distilled? (even if I reach the boiling point?)
    So, if I manipulate the temperature of the solution (by, say, placing the original in a water bath), then the only difference would be an increasing (or later decreasing) amount of aldehyde vapour, that is distilled off?
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    (Original post by ioffer007)
    But ethanoic acid will never be distilled? (even if I reach the boiling point?)
    So, if I manipulate the temperature of the solution (by, say, placing the original in a water bath), then the only difference would be an increasing (or later decreasing) amount of aldehyde vapour, that is distilled off?

    I meant if you dont distil it, you'll get ethanoic acid. Sorry if I wasn't clear.
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    (Original post by Libby18)
    I meant if you dont distil it, you'll get ethanoic acid. Sorry if I wasn't clear.
    No problem, I might be a dumb person in chemistry
    So, if I add ethanol to dicromate solution, and heat it up to 45º then will the distillate only be aldehyde?
    And if I will heat the solution up to 65º (still below the boiling point for ethanoic acid) will I get more distillate? (if I do two different distillation increments)
 
 
 
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