Major species present when fructose is dissolved in water

Alfa-fructofuranose and beta-fructofuranose

Explanation:

The species more stables in water of fructose are their cyclic forms. In aqueous solution, the ketone group of the fructose reacts in a reversible way with the hydroxyl group of the same forming a cyclic hemiketal, in a reaction of intramolecular cycling. These rings formed are more stables when contain 5 or 6 atoms, named furanose and pyranose forms, respectively. In this cycling process the carbonyl carbon (C=O) it is transformed into a chiral center which produces 2 possible anomers, alfa and beta. In the fructose, the hydroxyl group of the formed hemiketal it is produced in the carbon 2 (the anomeric carbon) and can be located above the ring or beneath the ring. In D-sugars (the most common in nature), when the hydroxyl group is located beneath the ring the structure is in the alfa form and when is above the ring is in the beta form.

In the case of fructose dissolved in water it is formed the alfa-fructofuranose an beta-fructofuranose in a majority way, as shown in the picture.

Sugars are capable of suffering of mutarotation when they are dissolved in water, which cause the interconversion of anomers alfa and beta, producing a mix of the alfa and beta forms in the furanose or pyranose rings. And the proportion of each

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