How is reducing sugar different to non-reducing sugar?
A reducing sugar contains a functional group which can donate electrons to reduce whatever accepts the electrons. Remember reduction is electron gain. In the Benedict’s test electrons from the reducing sugar are donated to the Cu++ (copper sulphate – CuSO4) in the Benedict’s solution which are reduced to Cu+ = red copper oxide which is the colour you see if the test is positive for a reducing sugar. Example is glucose which has a CHO (aldehyde group) which donates electrons (Glucose is an aldose). Non – reducing sugars do not have an available reducing group to react and donate electrons. Eg Sucrose is a disaccharide of glucose linked to fructose by a glycosidic bond and has no reducing group free. After ACID hydrolysis and subsequent neutralisation of the acid ( Benedict’s only works in alkaline conditions) the reducing groups are now available on the glucose and so it will now react witrh Benedict’s.
