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Homework Help: Basicity of certain sites

  1. Oct 16, 2006 #1
    I had a question given, regarding the basicity of certain sites on a molecule. For example, glycine:
    glycine_min.gif

    How would you determine whether the OH end or the NH2 end would be more "basic", or the first to get protonated?
     
  2. jcsd
  3. Oct 16, 2006 #2
    Make an analogy and think about

    1. CH3-OH
    2. CH3-NH2

    Which is more protonable?
    In case you didn't find the answer, try with

    1. H-OH = H2O
    2. H-NH2 = NH3

    Which is more protonable?
     
  4. Oct 16, 2006 #3
    What I'd like to know is how do I determine which is more protonable, without memorizing pka's.
     
  5. Oct 16, 2006 #4

    siddharth

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    Homework Helper
    Gold Member

    For the amino acids, one end has a carboxyl group (ie COOH) and the other end has the amino group. So, in this case, it's easy to figure out which end is acidic (ie, loses H+) and which end is basic (ie, accepts H+).
     
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