Question

Write the structure of \[\alpha - D - ( + ) - \] glucopyranose and \[\beta - D - ( + ) - \] glucopyranose.

Answer 1

Hint: These are the two cyclic forms of naturally occurring \[D - \left( + \right) - \] glucose and are diastereomers as they are not mirror images of each other. These differ only in the C1 Configuration and are thus known as anomers in carbohydrates.

Complete step-by-step answer:
Sugars in chemistry are described by using Haworth’s formula. The pyran and furan heterocyclic rings are resembled by pyranose and furanose oxide rings, having one of the positions is occupied by oxide.
Pyranose is used to depict saccharides that are six membered rings which have five carbon atoms and one oxygen atom in it. There can be other external carbons in the ring as substitutes.
To draw the structures of \[\alpha - D - ( + ) - \] glucopyranose and \[\beta - D - ( + ) - \] glucopyranose, a simple six-membered pyranose ring having five carbon atoms and one oxygen atom is drawn first. These structures were first suggested by Haworth and we call them Haworth projection formulae.
In the pyranose ring, \[C{H_2}OH\] group is added at the terminal, placed above the plane of the hexagon ring always. Groups which are present on the left-hand side in Fischer projection are placed above the plane of the ring and placed all the groups of right hand below the plane of the ring.

Due to this arrangement, a new asymmetric carbon atom is created at the carbonyl carbon and it is referred to as anomeric carbon atom. Anomers are two different configurations that are possible for the anomeric carbon atom. The position of OH group differs at C1 in both the structures. , where alpha stands for down OH group and beta for up OH group.

Note: Point to be remembered that groups which are on the right in a Fischer projection are written down in Haworth projection formulae while the groups which are on the left in a Fischer projection are placed above in Haworth projection.