Sugars can be classified as reducing or non-reducing; this classification is dependent on their ability to donate electrons
Reducing sugars can donate electrons (the carbonyl group becomes oxidised), the sugars become the reducing agent
Thus reducing sugars can be detected using Benedict’s test as they reduce the soluble copper sulphate to insoluble brick-red copper oxide
Examples of reducing sugars include: glucose, fructose and galactose
Fructose and galactose have the same molecular formula as glucose however they have a different structural formula
The different arrangement of atoms in these monosaccharides gives them slightly different properties
Non-reducing sugars cannot donate electrons, therefore they cannot be oxidised
To be detected non-reducing sugars must first be hydrolysed to break the disaccharide into its two monosaccharides before a Benedict’s test can be carried out
Example: sucrose
The mnemonic to remember the definitions for oxidation and reduction