Monday 19 May 2014

carbohydrate - glycoside formation







6 comments:

  1. This comment has been removed by the author.

    ReplyDelete
    Replies
    1. this conformation is more stable since lone pairs on ether oxygen in ring are anti to glycosidic bond that interacts via hyperconjugation

      Delete
    2. The general tendency of anomeric substituents to prefer an axial position is called Anomeric effect.

      For example, the α-methyl glucoside is more stable than the β-methyl glucoside due to hyperconjugation.

      In α-methyl glucoside, the non bonding HOMO with a pair of electrons on the ring oxygen is antiperiplanar to the antibonding LUMO of C-O bond in methoxy group. This allows hyperconjugation between them and thus by stabilizing the α-form.
      HOMO - highest occupied molecular orbital
      LUMO - lowest unoccupied molecular orbital

      Delete
  2. how can we tell that alpha-glycoside is a major product??

    ReplyDelete
  3. this conformation is more stable since lone pairs on ether oxygen in ring are anti to
    glycosidic bond that interacts via hyperconjugation

    ReplyDelete
  4. The general tendency of anomeric substituents to prefer an axial position is called Anomeric effect.

    For example, the α-methyl glucoside is more stable than the β-methyl glucoside due to hyperconjugation.

    In α-methyl glucoside, the non bonding HOMO with a pair of electrons on the ring oxygen is antiperiplanar to the antibonding LUMO of C-O bond in methoxy group. This allows hyperconjugation between them and thus by stabilizing the α-form.
    HOMO - highest occupied molecular orbital
    LUMO - lowest unoccupied molecular orbital

    ReplyDelete