Which of the following are anomers?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → α-D (+) Glucose and β-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 α-D-(+)-glucose and β-D-(+)-glucose are anomers.
Why the other options are incorrect
Option (2) D (+) Glucopyranose and D-(−) Fructofuranose — Incorrect. These are ring forms of two different sugars (an aldose and a ketose), not two forms of one sugar differing at C-1.
Option (3) D (+) Glucose and D (−) Fructose — Incorrect. Both are \( \ce{C6H12O6} \), but glucose has an aldehyde group and fructose a ketone group, so they are functional isomers.
Option (4) Galactose and Amylose — Incorrect. Galactose is a monosaccharide, while amylose is a polysaccharide (a component of starch) made of glucose units; they are not even isomers.
NCERT (2026-27 edition):
Glucose – …
