Cyclic Structure of Glucose – Anomers

We know monosaccharides have cyclic hemiacetal or hemiketal structures. To illustrate, let us first consider the example of D-glucose. During hemiacetal formation C₅ – OH of glucose combines with the C₁ – aldehydic group. As a result, C₁ becomes chiral or asymmetric and thus has two possible arrangements of H and OH groups around it. In other words, D-glucose exists in two stereoisomeric forms, i.e., α-D-glucose and β-D-glucose as shown below:
In α-D-glucose, the OH group at C₁ is towards right while in β-D-glucose, the OH group at C₁ is towards left. Such a pair of stereoisomers which differ in configuration only around C₁ are called anomers and the C₁ carbon is called Anomeric carbon (or glycosidic carbon.  The cyclic structures of monosaccharides can be better represented by Haworth Projection formulae. To get such a formula for any monosaccharide (say α-and β-D-glucose), draw a hexagon with its oxygen atom at the upper right hand corner. Place all the groups (on C₁, C₂, C₃ and C₄) which are present on left hand side in structures I and II, above the plane of the ring and all those groups on the right hand side below the plane of the ring. 
The terminal – CH₂OH group is always placed above the plane of the hexagon ring (in D-series). Following the above procedure, Haworth Projection Formulae for α-D-glucose (I) and β-D-glucose (II) are obtained as shown below: