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Chemistry LibreTexts

SC8. Biological Building Blocks: Carbohydrates

  • Page ID
    4133
  • SC8. Biological Building Blocks: Carbohydrates

     

    • The naturally-occurring carbohydrates are chiral.
    • Glyceraldehyde is the grandmother of carbohydrates.

     

     

    Wire Frame

    Ball & Stick

    Spacefilling

     

    Wire Frame

    Ball & Stick

    Spacefilling

    • The "last" chiral center in other carbohydrates all have the same configuration as the chiral center in glyceraldehyde.

    • Fischer projections are drawings that are sometimes used to show stereochemistry in a different way.
    • The groups to left and right of the Fischer projection are coming towards you.
    • The groups on top and bottom are going away from you.
    • The carbon chain is drawn vertically with attachments at the sides.
    • Normally, the chain is oriented so that the "highest priority functional group" on the chain is at or near the top of the chain; that usually means the group with the most bonds to oxygen.  In glyceraldehyde, the CH=O group is drawn at the top rather than at the bottom.
    Problem SC8.1.

    What is the absolute configuration of L-glyceraldehyde?  What about D-glyceraldehyde?

    Problem SC8.2. 

    Draw the following molecules as Fischer projections.

    Problem SC8.3. 

    Convert the following Fischer projections into wedge-dash drawings.