Chapter 20, Problem 20.50AP

Interpretation Introduction

Interpretation:

The cyclic hemiacetal $\alpha \text{ and }\beta$ forms of given open chain D-mannose has to be drawn.

Concept introduction:

• Haworth projection is used to represent sugars in their cyclic forms.
• In Haworth projection,
• $\text{α}$-indicates the $–OH$ group of anomeric carbon $C1$ and ${\text{CH}}_{\text{2}}\text{OH}$ substituent on the $C5$ carbon is trans to each other. $\beta$-indicates the $–OH$ group of anomeric carbon $C2$ and ${\text{CH}}_{\text{2}}\text{OH}$ substituent on the $C5$ carbon is cis to each other.
• D indicates the ${\text{CH}}_{\text{2}}\text{OH}$ substituent on the $C5$ carbon is on up position.
• The right side and left side $–OH$ groups of chiral carbons in fisher projection are drawn as down side and upward side respectively.
• Mutarotation is the change of specific rotation of an anomer when dissolved in water. It is due to the equilibrium formation of two anomeric forms and open chain form.
• An open chain structure of a sugar can produces two hemiacetal projections due to the two anomers, such as $\alpha and\beta$.