Question

Which is the correct chair form for the β-anomer of D-mannose?

Answer 1

In the chair form for the β-anomer of D-mannose, the hydroxyl group present on the anomeric carbon is in the cis position to the $CH_{2} O$ group.

• The chair form of the cyclohexane, D-mannose is considered a very stable conformation with no torsional strain.

• The chair structure is made up of a six-membered ring with each C-C bond in a staggered configuration.

• Mannose is a sugar molecule in the aldohexose group of carbohydrates that is a C2 epimer of glucose.

• Due to the fact that D and L-mannose are enantiomers, they will be mirror images of one another. As a result, D-mannose will have a mirrored structure to L-mannose.

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Answer 2

The hydroxyl group on the anomeric carbon is in the cis position to the $CH_{2} O$ group in the chair form of the β-anomer of D-mannose.

Explanation:

• An extremely stable conformation without torsional strain is thought to exist in the chair form of the cyclohexane, D-mannose.
• Each C-C bond in the six-membered ring that makes up the chair structure is spaced out differently.
• Mannose is a C2 epimer of glucose and belongs to the aldohexose family of carbohydrates.
• D and L-mannose will be mirror images of one another because they are enantiomers.
• D-mannose will consequently have a structure that is identical to L-mannose.

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