Q.Write the structure of the following : $\alpha$-D-glucopyranose and $\beta$-D-glucopyranose

D-glucose exists predominantly in cyclic (pyranose) form, formed by intramolecular hemiacetal formation between the C-5 -OH and the C-1 aldehyde; the two possible orientations of the new C-1 -OH give rise to the alpha and beta anomers.

D-glucose, in its open-chain form, is an aldohexose ($CHO-(CHOHx4)-CH_2OH$). In aqueous solution, the -OH group on C-5 attacks the aldehyde carbon (C-1) intramolecularly, forming a six-membered (pyranose) ring hemiacetal. This creates a new stereocentre at C-1 (the anomeric carbon), giving two possible diastereomeric forms called anomers:

• $\alpha$-D-glucopyranose: in the Haworth projection, the -OH at C-1 points downward (on the opposite side to the -CH$_2$OH at C-5, i.e. below the ring plane, trans/axial-like arrangement).
• $\beta$-D-glucopyranose: in the Haworth projection, the -OH at C-1 points upward (on the same side as the -CH$_2$OH at C-5, i.e. above the ring plane). …