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How do you determine the pKa values of novel bases?

  1. Dec 21, 2013 #1
    Imagine there is a reaction performed and it contains a product that is easily separable via an acid base extraction. This product is only formed in 50% yield. The other 50% formed unwanted products that are to be separated and done away with.

    If all that is known is the structure of these unknown molecules, how can they be extracted? I figure knowing the pKa values would be useful. Assuming the unwanted molecule is also soluble in the organic layer like the wanted molecule, and neither can be distilled out, the right acid could be selected to cause a salt to form of the wanted molecule but not the unwanted molecule.

    My question is, how does one determine the pKa value off a molecule with no experimental data when only the structure is known? I can post pictures of the molecule shortly, but regardless of that, is there a way to determine pKa value off structure?

    What would be really useful is if there was some sort of program that could analyze the structure of a molecule and determine when it is a solid/liquid/gas and the related temperatures of phase change. Anyone know of such a thing? I know Chemspider.com has a way to predict these values of molecules that are already in their database, but I have found no way to allow it to predict new molecules.
  2. jcsd
  3. Dec 21, 2013 #2


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    Staff: Mentor

    5 seconds googling, second link: http://www.uiowa.edu/~quantum/omtkypka.pdf [Broken]
    Last edited by a moderator: May 6, 2017
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