Hey there Sign in to join this conversationNew here? Join for free

Determining D or L Carbohydrates...

Announcements Posted on
    • Thread Starter
    • 0 followers
    Offline

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

    Thanks!:o:
    • 0 followers
    Offline

    ReputationRep:
    (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).
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    OMG! Thank you so much, my brain is RESTING now.
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (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?
    • 0 followers
    Offline

    ReputationRep:
    (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.
    • 0 followers
    Offline

    ReputationRep:
    (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.

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?

    this is what you'll be called on TSR

  2. this can't be left blank
    this email is already registered. Forgotten your password?

    never shared and never spammed

  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide the button to the right to create your account

    Slide to join now Processing…

Updated: April 19, 2009
New on TSR

Your favourite film of the year?

For you personally what has been the best 2014 movie

Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.