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Why is methyl red soluble in water AND ether?

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  1. Feb 15, 2016 #1
    • Please post this type of questions in the HW section using the template.
    I just had an extraction lab, and am confused how methyl red is soluble in both water and ether.
    My prediction was that methyl red would be only soluble in ether, but it actually dissolved into both layers. Looking at it's structure, it has a carboxylic group on one end, attached to a chain consisting of aromatics with some nitrogens. Any suggestions or guidance?
     
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  3. Feb 15, 2016 #2

    Borek

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    Staff: Mentor

    Can it get ionized?
     
  4. Feb 15, 2016 #3

    epenguin

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    As it is an indicator I don't need to know its structure to answer that question! :oldbiggrin:
    I wouldn't be so surprised about it dissolving in ether - after all water and ether are up to a point miscible.
    Since this was in the lab it occurred to me that there could be some slightly interesting physical chemistry observations and predictions about the colour when you dissolve some acids or bases in the ether with it -but everything would need to be absolutely anhydrous for this to be significant.
    I wonder, could you find conditions where it is a different colour in the two phases?
     
  5. Feb 17, 2016 #4
    Well doing a little bit of reading, I found out that in it's solid phase, methyl red is soluble in ether, but miscible in water... not sure if this is relevant at all to my observations.
     
  6. Feb 17, 2016 #5
    No it can't. The pKa of methyl red is 4.95, so in distilled water it does not ionize. So I am guessing then, that in a solution of ether and water, it will remain in it's uncharged state, and only be found in the ether layer?
     
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