Question

When a monosaccharide forms a cyclic hemiacetal, the carbon atom that contained the carbonyl group is identified as the ______ carbon atom, because:

• A. $D$, the carbonyl group is drawn to the right
• B. $L$, the carbonyl group is drawn to the left
• C. Acetal, it forms bond to an $-OR$ and an $-O{R}^{{}^{\prime }}$
• D. Anomeric, its substituents can assume an $\beta$ or $\alpha$ position

Answer 1

The correct option is D Anomeric, its substituents can assume an $\beta$ or $\alpha$ position

When two cyclic forms of a carbohydrate differ in configuration only at hemiacetal carbons, they are said to be anomers. Thus, anomers are cyclic forms of carbohydrates that are epimeric at hemiacetal carbon and this carbon ($C-1$ of aldose) is called anomeric carbon.