The anomer of β-D-glucose is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → α-D-glucose.
Glucose exists mainly in a six-membered ring (pyranose) form, formed when the C-5 –OH adds to the C-1 aldehyde group. This makes C-1 a new chiral centre, the anomeric carbon, so two cyclic forms are possible:
α-D-glucose: the –OH at C-1 is on the right in the cyclic Fischer projection (below the ring in the Haworth projection).
β-D-glucose: the –OH at C-1 is on the left in the cyclic Fischer projection (above the ring in the Haworth projection).
Two such forms that differ only in the configuration at the anomeric carbon (C-1) are called anomers. So the anomer of β-D-glucose is α-D-glucose.
Why the other options are incorrect
Option (1) β-D-mannose — Incorrect. Mannose differs from glucose in the configuration at C-2; such sugars are epimers, not anomers.
Option (2) α-D-galactose — Incorrect. Galactose differs from glucose at C-4 (the C-4 epimer), besides the C-1 change.
Option (3) α-D-mannose — Incorrect. It differs from β-D-glucose at two carbons, C-1 and C-2, so it is neither its anomer nor a simple epimer.
NCERT (2026-27 edition):
Cyclic Structure of Glucose – …
