Benedict's Test for Reducing Sugars

Benedict's Test

• Identifies reducing sugars (monosaccharides) with free ketone or aldehyde functional groups.
• Reducing sugars, like glucose, can transfer hydrogens (electrons) to other compounds, causing a reduction reaction.

Characteristics of Reducing Sugars

• All monosaccharides are reducing sugars due to their exposed carbonyl group.
• Some disaccharides, like sucrose, are non-reducing sugars and won't react with Benedict's reagent.
• Large polymers of glucose, such as starch, are not reducing sugars.

Principle of Benedict's Test

• Heating Benedict's solution with simple carbohydrates causes a color change to orange-red/brick-red.
• Copper (II) ions in the solution are reduced to Copper (I) ions, leading to the color change.
• Red copper(I) oxide formed is insoluble in water and precipitates out of solution, forming a precipitate.

Benedict Reagent

• Sodium carbonate provides alkaline conditions necessary for the redox reaction.
• Sodium citrate complexes with copper (II) ions to prevent deterioration to copper(I) ions during storage.

Objective and Specificity

• The objective of Benedict's test is to distinguish between reducing and non-reducing sugars.
• Benedict's test is specific for reducing sugars.