Fructose has the molecular formula C₆H₁₂O₆ and contains a ketonic functional group at carbon number 2. It shares similarities with glucose in having six carbons in a straight chain.

Fructose is obtained along with glucose by the hydrolysis of the disaccharide sucrose. It is a natural monosaccharide present in fruits, honey, and vegetables.

The existence of two crystalline forms (a and b) with different melting points (419 K and 423 K) cannot be explained by the open-chain structure (I). The proposal of a cyclic hemiacetal structure forming a six-membered ring, with —OH at ...

Glucose’s pentaacetate does not react with hydroxylamine, indicating the absence of a free —CHO group. This contradicts the open-chain structure (I) and suggests a different configuration.

Glucose does not react with Schiff’s test or form a hydrogensulphite addition product due to the absence of a free —CHO group. The open-chain structure (I) fails to explain these observations.