Question

Formation of pyranose structure from glucose leads to formation of diastereoisomers called

• A. Anomers
• B. Epimers
• C. Tautomers
• D. Metamers

Answer 1

The Correct Option is A

The given question asks about the type of diastereoisomers formed when glucose adopts a pyranose structure. Let us go through the concepts to understand why the correct answer is Anomers.

Concept Explanation

In glucose, the formation of a cyclic structure, such as a pyranose form, occurs when a hydroxyl group reacts with the carbonyl group, resulting in a hemiacetal structure. When glucose adopts this pyranose form, it can form two different configurations at the anomeric carbon (C-1 in aldoses like glucose)

Anomers

Anomers are a specific type of diastereomer, which differ in configuration only at the anomeric carbon. In glucose, the anomeric carbon is the first carbon atom (C-1) in the ring. The two different configurations at this carbon are termed as the α-anomer and β-anomer.

• The α-anomer has the -OH group on the anomeric carbon (C-1) trans to the CH₂OH group.
• The β-anomer has the -OH group on the anomeric carbon (C-1) cis to the CH₂OH group.

Why Other Options are Incorrect

1. Epimers: These are diastereomers that differ in configuration at any single stereogenic center other than the anomeric carbon. For example, D-glucose and D-galactose are epimers.
2. Tautomers: These are isomers that differ in the placement of protons and electrons, typically involving a keto-enol tautomerism, which is not applicable in the formation of pyranose rings from glucose.
3. Metamers: These are isomers with different alkyl groups on either side of a heteroatom (such as oxygen or sulfur), mostly related to structural isomerism in organic chemistry, which is irrelevant here.

Conclusion

Hence, the correct answer is Anomers, as they are the specific diastereomers formed due to the variation at the anomeric carbon in the pyranose form of glucose.