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Amino acids as acid/base

  1. Mar 31, 2012 #1
    1. The problem statement, all variables and given/known data

    How does the following reaction demonstrate an amino acid as an acid:
    H2NCH2COOH + CH3OH → H2NCH2COOCH3 + H2O

    How does the following reaction demonstrate an amino acid as a base:
    H2NCH2COOH + CH3COCl → CH3CONHCH2COOH + HCl

    2. Relevant equations



    3. The attempt at a solution
    An acid is a species that DONATES a proton and a base is a species that ACCEPTS a proton

    In both situations it seems more like an esterfication reaction than an acid / base reaction.

    Also in the second reaction the H2N loses an H+ for water (I would call that acidic behaviour but it is actually basic behaviour) and the first example COOH loses OH (basic behaviour but is classified as acidic)

    I am confused :S
     
  2. jcsd
  3. Apr 1, 2012 #2

    Borek

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    Staff: Mentor

    This is not about a standard Bronsted acid definition. Think outside of the box. What is an ester?

    That's what they ask about, doesn't mean I like the question.
     
  4. Apr 1, 2012 #3
    well an ester is a type of condensation reaction in which a small molecule is eliminated?
     
  5. Apr 1, 2012 #4

    Borek

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    Staff: Mentor

    No, ester is not a type of a reaction. It is a product of a reaction. Reaction of what with what?
     
  6. Apr 1, 2012 #5
    a carbonyl carbon (e.g: COOH or COCl) and a hydrogen attached to an electronegative atom (e.g: OH, H2N)
     
  7. Apr 1, 2012 #6
    In fact another site says its when the hydrogen of an organic acid is replaced by an organic group (e.g: alkyl)

    BUT the acid LOSES OH not just the H???
     
  8. Apr 1, 2012 #7

    Borek

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    Staff: Mentor

    The other site is wrong. That is, it is wrong when you look at the mechanism, but it is OK when you look just at the product structure.

    Ester is produced by a reaction of an acid (even doesn't have to be organic - think sulfuric, phosphoric) with an alcohol.
     
  9. Apr 2, 2012 #8
    ok so I get the first one but how does the second rxn demonstrate basic behaviour?
     
  10. Apr 2, 2012 #9

    Borek

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    Staff: Mentor

    To be honest - I don't see how. I told you I don't like the question.
     
  11. Apr 2, 2012 #10
    nm
    thanks for your help :)
     
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