Chapter 20.4, Problem 20.11P

Interpretation Introduction

Interpretation:

For the given hemiacetal form of a monosaccharide, all the carbon atoms has to be numbered, the anomeric carbon atom has to be identified and whether it is a $\alpha or\beta$ anomeric form has to be given

Concept introduction:

• Monosaccharides forms cyclic hemiacetals, the oxygen atom in the $–OH$ group of second last carbon (from bottom) attacks the carbonyl group of the same compound.
• The carbon atom in carbonyl group of monosaccharides is called anomeric carbon.
• Haworth projection is used to represent sugars in their cyclic hemiacetal 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.