The formation of the furanose structure of fructose involves the intramolecular interaction of functional groups present at which of the following carbon atoms?

Step-by-step solution

Fructose is a ketohexose with the ketonic carbonyl group located at C-2. To form a five-membered furanose ring, an intramolecular hemiketal formation takes place. The hydroxyl group ( -OH ) present at C-5 attacks the carbonyl carbon at C-2. This interaction results in a cyclic structure containing four carbon atoms (C-2, C-3, C-4, C-5) and one oxygen atom, which is characteristic of a furanose ring.