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Difference between alpha-keto acid and keto acid

  1. Mar 22, 2009 #1
    1. The problem statement, all variables and given/known data
    What is the difference between alpha-keto acid and keto acid?

    3. The attempt at a solution
    I know that the difference is that alpha-keto acid contains an alpha carbon.
    However, I do not know what the alpha carbon is in this case, and how I can show it.
     
  2. jcsd
  3. Mar 23, 2009 #2

    Borek

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    Staff: Mentor

    What is alpha carbon in other cases?
     
  4. Mar 23, 2009 #3
    You can have alpha carbon, for example, in glucose and maltose.
     
  5. Mar 23, 2009 #4

    Borek

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    What makes this carbon 'alpha'? Why is it called this way? How does it differ from 'beta'?
     
  6. Mar 23, 2009 #5
    I found the answer in Wikipedia.
    Alpha keto-acid has keto group next to COOH, while beta keto-acid has keto group at the second Carbon from COOH.

    The LHS molecule is alpha-keto acid, while RHS is beta-keto acid in the following picture.
    http://dl.getdropbox.com/u/175564/alpha-beta-acids.png [Broken]

    Note that keto group in the RHS molecule is at the third carbon that is the second C from COOH.

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    Is everything correct?
     
    Last edited by a moderator: May 4, 2017
  7. Mar 23, 2009 #6

    Borek

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    If you were looking for the answer in wikipedia, it would be better to start at the very beginning:

    http://en.wikipedia.org/wiki/Alpha_carbon

    Other left.
     
    Last edited by a moderator: May 4, 2017
  8. Mar 23, 2009 #7
    Thank you!

    So we have both alpha and beta carbons in both molecules
    http://dl.getdropbox.com/u/175564/alpha-beta-carbons-updated.png [Broken]

    ---
    Is the carbons now correctly labeled with alpha and beta carbons?
     
    Last edited by a moderator: May 4, 2017
  9. Mar 23, 2009 #8

    Borek

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    OK now.

    As you see concept of 'alpha'. 'beta' and 'gamma' carbons is widely used in chemistry. Not very formal, often very useful.
     
  10. Mar 23, 2009 #9
    I am unsure about alpha and beta carbons in http://www.laakis.com/wp-content/uploads/2008/12/picture-7.png" [Broken].

    It seems that the same naming convention does not apply here.
    Instead, the position of OH group seems to determine the name.
     
    Last edited by a moderator: May 4, 2017
  11. Mar 23, 2009 #10

    Borek

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    Yes. As I told you - it is not formal. Still, widely used. See GHB for example.
     
  12. Mar 23, 2009 #11

    Ygggdrasil

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    The alpha and beta conventions for sugars is completely different from the alpha, beta, gamma, etc. nomenclature that you were discussing previously.

    For cyclic sugars, alpha refers to a cyclized sugar in which the OH group of the anomeric carbon (the carbon with two bonds to oxygen) is on the opposite side of the ring as the alkyl group on the ring.
     
  13. Mar 24, 2009 #12
    Thank you both!
     
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