What is the structural difference between α-D-glucopyranose and β-D-glucopyranose, which defines them as anomers?

Answer and explanation

Correct answer: B. They differ in the spatial configuration of the -OH group at the C-1 anomeric carbon

  1. Step 1: In the cyclic hemiacetal form of D-glucose (glucopyranose), cyclization between the C-1 aldehyde carbon and the C-5 hydroxyl group generates a new stereocenter at C-1.
  2. Step 2: This newly created asymmetric carbon atom is termed the anomeric carbon.
  3. Step 3: In -D-glucopyranose, the group at C-1 lies trans to the group (pointing downward in the Haworth projection).
  4. Step 4: In -D-glucopyranose, the group at C-1 lies cis to the group (pointing upward in the equatorial position in the Haworth projection).
  5. Step 5: Diastereomers that differ in configuration only at the hemiacetal/anomeric carbon are defined as anomers.
Answer
They differ exclusively in the spatial configuration of the hydroxyl group (-OH) at the C-1 anomeric carbon atom
Why not the others: 'They differ at the C-5 carbon atom' is false because C-5 configuration determines D/L family; 'They differ in the number of carbon atoms...' is false as both are 6-carbon pyranose hexoses; 'One is an open-chain aldehyde...' is incorrect as both are cyclic pyranoses.

Practise more Biomolecules and Polymers.

Free questions with an explanation for every one, and full timed NEET UG mock tests.

All Biomolecules and Polymers questionsTake a mock test

More Biomolecules and Polymers questions