Biomolecules - Monosaccharides (Glucose and Fructose)

Monosaccharides are the simplest carbohydrates that cannot be hydrolyzed into smaller units. Their general formula is $(CH_2O)_n$.

Glucose ($C_6H_{12}O_6$) is an aldohexose, meaning it contains an aldehyde group ($-CHO$) and six carbon atoms.

The open-chain structure of Glucose was established through chemical reactions: heating with $HI$ yields $n$-hexane, proving a straight chain of six carbons; reaction with $NH_2OH$ yields an oxime, proving a carbonyl group.

Mild oxidation of Glucose with bromine water ($Br_2/H_2O$) produces Gluconic acid, confirming the carbonyl group is an aldehyde.

Strong oxidation of Glucose with nitric acid ($HNO_3$) produces Saccharic acid (a dicarboxylic acid), indicating the presence of a primary alcoholic group ($-CH_2OH$).

Glucose exists in two cyclic hemiacetal forms, $\alpha$-$D$-glucose and $\beta$-$D$-glucose, which differ only in the configuration of the hydroxyl group at $C_1$. These isomers are called anomers.

Fructose ($C_6H_{12}O_6$) is a ketohexose. It contains a ketonic functional group at $C_2$ and is naturally laevorotatory, hence often called laevulose.

While Glucose forms a six-membered pyranose ring, Fructose typically forms a five-membered furanose ring in its cyclic state.

Mutarotation is the spontaneous change in the specific rotation of an optically active compound (like $\alpha$ or $\beta$ glucose) when dissolved in water, until an equilibrium is reached.