Organic Chemistry MCAT Practice Exam

What are anomers specifically related to?

1. Differences in molecular mass

2. Differences in symmetry

3. Differences at one chiral center in sugars

4. Nonsuperimposable mirror images

The correct answer is: Differences at one chiral center in sugars

Anomers are a specific type of stereoisomer that differ at one chiral center, specifically the anomeric carbon, which is the carbon that becomes chiral when a cyclic structure forms from an aldose or a ketose sugar. This occurs during the cyclization of monosaccharides, where the hydroxyl (-OH) group attached to the anomeric carbon can be oriented either above or below the plane of the sugar ring, leading to the formation of two distinct forms: alpha (α) and beta (β). Thus, the choice referring to differences at one chiral center in sugars accurately captures the essence of what anomers are, as they specifically represent this variation in configuration at the anomeric carbon in carbohydrate chemistry. The other options do not correctly pertain to anomers; they do not involve structural differences related strictly to chiral centers or sugars. For example, differences in molecular mass concern the weight of the molecules rather than stereochemistry, differences in symmetry involve chirality but do not specifically relate to the concept of anomers in sugars, and nonsuperimposable mirror images refer more broadly to enantiomers rather than the specific context of anomers in carbohydrate chemistry.