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My solution consisted of sorbicillinol and water, sorbicillinol being a polar substance. I wanted to isolate sorbicillinol from water using liquid-liquid extraction.

For my solvent I used ethyl acetate. Pouring the ethyl acetate in my separatory funnel resulted in a clear separation of the organic layer (being sorbicillinol) and the aqueous layer (being water and ethyl acetate).

However I don't fully understand the theory behind this. All of these substances are polar, the only difference between the substances being the density. Why did the water go to ethyl acetate. Did it have a stronger polar interaction to it?

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    $\begingroup$ According to this article, sorbicillinol cannot be concentrated without causing decomposition. Thus, I assume your sorbicillinol in organic extract may undergoes reactions like Diels=Alder to give dimer or trimer. It certainly looks more stable in water. $\endgroup$
    – Mathew Mahindaratne
    Commented Jan 7 at 9:34

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The key point is that the solubility of organic compounds in water, even partially polar ones, often has an upper limit (exceptions include ethanol). For instance, ethyl acetate is soluble in water, but only to a limit (8.3 g/100 mL). If you surpass that limit, adding more ethyl acetate does not significantly change the amount or concentration in the aqueous phase (the water layer, assumed constant in volume).

In addition, solubility typically depends on temperature. For ethyl acetate in water it is lower as you decrease T. You can therefore chill a mixture to reduce the amount of ethyl acetate in water.

Similar principles apply to the solubility of organic compounds such as sorbicillinol in water and in ethyl acetate. In this case the amount of the organic compound may be so low or solubility so high that saturation (as in the case of ethyl acetate in water just discussed) does not occur, but all the same the organic compound partitions between the separate layers (water and ethyl acetate), and the ratio of the concentrations in each layer is approximately constant (the ratio being called the partition constant), regardless of their volumes, the important thing being that two phases form. It means that as you add more ethyl acetate, saturating the water and forming a separate phase, an increasing amount of the organic compound (sorbicillinol) ends up in the organic phase (ethyl acetate). You can add more of this solvent to increase partition away from water and thereby your yield (to a point). That's because the total amount in each phase is the product of concentration and volume in that phase.

From PubChem, the relative partition of the organic compounds in water are:

ethyl acetate XLogP3: 0.7
sorbicillinol XLogP3-AA: 1.8

These values imply that sorbicillinol is less polar (less water soluble, more octanol soluble) than ethyl acetate. Since ethyl acetate is less polar than water, this also implies that sorbicillinol will prefer to be in ethyl acetate. Note also that while it helps if the organic compound highly prefers the ethyl acetate, it is not absolutely necessary. You often wash your reaction mixture more than once to extract the product.

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It would say it is rather (water + sorbicillinol) + (ethyl acetate) -> (water) + (ethyl acetate + sorbicillinol).

Some substances are more polar than other. Like there is not just white and black, but also the whole continuous scale of gray.

Sorbicillinol polarity is more similar to polarity of ethyl acetate than to water, so the extraction equilibrium prefers the ethyl acetate.

Sorbicillinol (pubchem.ncbi.nlm.nih.gov):

sorbicillinol from pubchem.ncbi.nlm.nih.gov

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