Benedict Test
The Benedict’s test identifies reducing sugars (monosaccharide ), which
have free ketone or aldehyde functional groups.
Some sugars such as glucose are called reducing sugars because they
are capable of transferring hydrogens (electrons) to other compounds,
a process called reduction. When reducing sugars are mixed with
Benedicts reagent and heated, a reduction reaction causes the
Benedicts reagent to change color.
-All monosaccharide is reducing sugar since they have exposed carbonyl
group
-Some disaccharide have exposed carbonyl group so they reducing
sugar ,other like sucrose are non reducing sugar and will not react with
benedict reagent
-Large polymers of glucose such as starch are not reducing sugar
Objective to distinguish between reducing and non reducing sugar –
benedict test is specific for reducing sugar
Principle of Benedict’s Test
When Benedict’s solution and simple carbohydrates are heated, the
solution changes to orange red/ brick red. This reaction is caused by the
reducing property of simple carbohydrates. The copper (II) ions in the
Benedict’s solution are reduced to Copper (I) ions, which causes the
color change.The red copper(I) oxide formed is insoluble in water and is
precipitated out of solution. This accounts for the precipitate formed.