Question

Identify the compound from the Haworth projection shown.

(a) α-D-(+)-glucopyranose

(b) β-D-(+)-glucopyranose

(c) α-D-(-)-fructopyranose

(d) β-D-(-)-fructopyranose

This question was addressed to me during a job interview.

Origin of the question is Biomolecules Carbohydrates topic in division Biomolecules of Chemistry – Class 12

Answer 1

The correct choice is (d) β-D-(-)-fructopyranose

For explanation I would say: This is the pyranose structure of fructose, where the C2 keto group and C6 OH group are involved in cyclisation. The α and β forms in this structure differ based on the arrangement of CH2OH and OH groups around the C2 carbon. Since in this compound, the OH at C2 is in the same side as the OH at C3, it is the β-form.