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# Write short notes on reducing and non-reducing sugars.

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## Reducing Sugar Reducing sugar is one that possesses a free aldehyde or ketonic group.It can reduce Fehling and Tollens reagent.Fehling A is Copper sulfate $\left({\mathrm{CuSO}}_{4}\right)$and Fehling B is an aqueous solution of potassium sodium tartrate $\left({\mathrm{KNaC}}_{4}{\mathrm{H}}_{4}{\mathrm{O}}_{6}·4{\mathrm{H}}_{2}\mathrm{O}\right)$.Tollens's reagent is the ammoniacal solution of silver nitrate $\left(\left[\mathrm{Ag}{\left({\mathrm{NH}}_{3}\right)}_{2}{\right]}^{+}\right)$Reducing sugar can act as a reducing agent. It can be further reduced to alcohol.For example maltose and lactose.Non reducing sugarIn a basic aqueous solution, a non-reducing sugar is not reduced by a weak oxidising agent (one that oxidises aldehydes but not alcohols, such as Tollen's reagent).There is no free aldehyde or ketonic group.Non-reducing sugars do not have an $-\mathrm{OH}$ group attached to the anomeric carbon so they cannot reduce other compounds. E.g. sucrose and RaffinoseThe structure of sucrose is as follows:-

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