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Determining D or L Carbohydrates...

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    How can you tell if a Carbohydrate is D or L? Which part of the molecule gives you the direction info?

    Thanks!:o:
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    (Original post by carmeyeii)
    How can you tell if a Carbohydrate is D or L? Which part of the molecule gives you the direction info?

    Thanks!:o:
    Monosaccharide carbohydrates are an aldehyde or ketone with many alcohol groups, one each carbon (is that right? I've only seen that so far). The rule for carbohydrates is that on the Fischer projection, the -OH group on the chiral carbon furthest away from the carbonyl (aldehyde or ketone) is either on the left (L) or on the right (D).
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    OMG! Thank you so much, my brain is RESTING now.
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    (Original post by michaelyus)
    Monosaccharide carbohydrates are an aldehyde or ketone with many alcohol groups, one each carbon (is that right? I've only seen that so far). The rule for carbohydrates is that on the Fischer projection, the -OH group on the chiral carbon furthest away from the carbonyl (aldehyde or ketone) is either on the left (L) or on the right (D).
    One more question...

    What qualifies as a chiral carbon? Does it have to have ALL functional groups different?
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    (Original post by carmeyeii)
    One more question...

    What qualifies as a chiral carbon? Does it have to have ALL functional groups different?
    Carbon can make four covalent bonds. So for a particular carbon, if each of the four groups bonded to that carbon are different, then that particular carbon is chiral.
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    (Original post by carmeyeii)
    How can you tell if a Carbohydrate is D or L? Which part of the molecule gives you the direction info?

    Thanks!:o:
    As someone said before, the furthest chiral carbon from the carbony group. Once you remember that just remember that L is for left(think to yourself Left) and D is right because the latin word for right is DEXTRA. If you can remember that you should be fine.

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