CHEM10006 Lecture Notes - Lecture 28: Nucleobase, Anomer, Reducing Sugar
10 Aug 2018
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Document Summary
The biggest difference between carbohydrate molecules is whether the groups are axial or equatorial. Number of carbons (tri, tetra, penta, hexa etc) Used instead of the r/s nomenclature because it is significantly simpler for these molecules. Monosaccharides exist in an equilibrium between the linear form and the cyclic form, with preference for the cyclic form. The linear molecule is cyclised by an intramolecular hemiacetal formation reaction. An alcohol attacks an aldehyde or ketone. Since carbonyl groups are sp2 hybridised, they are planar, and the hydroxyl can attack from either side giving 2 possible stereoisomers called anomers. The carbon is thus an anomeric centre. Haworth configurations are 2d configurations of chair isomers. Place anomeric carbon in the right and ch2oh on the top, pointing up. If the oh group on the anomeric centre points down and is trans, it is the alpha anomer.
