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Thread: Chromatography charges

  1. #1 Chromatography charges 
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    Hi,

    Trying to write up an assignment on this, but seem to be going in cicles with the charges and how capilary action works on a solvent (in this case propanone with petroleum ether), which in turn pulls up the pigments.

    As I see it, the OH groups in cellulose are negatively polar, which attract the Oxygen in Propanone (isn't oxygen always -ve though??). The hydrocarbon tail of propanone pulls the petroleum ether hydrocarbon with it, through dispersion, which in turn pulls the pigments???

    I think I've got quite confused over this.

    Any speedy clarification would be amazing.


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  3. #2  
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    The OH groups are trying to use the hydrogen in the solvent to become HOH

    Are you ignoring the effect of the water molecules that are on the paper too?
    The cellulose is strongly attractive to water and if you are using non-polar solvents the water attached to the surface of the cellulose probably matters more than the reaction to the OH in the cellulose does to it.
    The water layer on the cellulose fibres could be thought of as similar to a thin film chromatography method.

    The polar molecules dissolved in the solvent dissolve into the water more easily and that slows them down so they separate according to how easily they dissolve in water.

    I hope somebody corrects any errors I made because I am not a chemist


    Last edited by dan hunter; March 2nd, 2014 at 04:45 PM.
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  4. #3  
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    We are disregarding water in this explanation. Also, propanone is polar.
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  5. #4  
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    dipole-dipole bonding?
    Hydrogen bonding?

    Sorry I can't just give you an easy answer like I was a trained chemist.
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