Reducing and non-reducing sugars. (1 Viewer)

[Bob.]

Hey whats the chemical differences between these. Is it something to do with when they are in their straight chain forms as apposed to their hexagon structures?

 

[Naylyn]

This may be a stupid question...what do you mean by reducing and non reducting sugars?

 

[Bob.]

reducing as in redox. but i need to know why chemically why a sugar would act as a reducing agent or not act like one.

 

[Tim035]

Many sugars alternate between a closed ring and open chain form. In the open chain form sugars with a carbon double bonded to an oxygen are powerful oxidising agents and thus are able to reduce other chemicals in solution. In the closed chain form these sugars contain a hydroxide group joined to the same carbon as the terminal oxygen. Such examples are glucose, maltose, fructose and most monosaccharides. Sucrose is an example of a non reducing sugar as bonding occurs through the hydroxide groups on the carbonyl carbon atom of both the glucose and fructose unit, thus no carbon atom contains both a hydroxide and oxygen group attached to it.

To test for a reducing sugar place a small amout of the solution to be tested in a test tube and add 2- 3 drops of benidicts solution. Lightly warm in a water bath for a period of 5 minutes (do not let the water bath boil as then any di or polysaccharides will hydrolyse producing possibly false results). If it is a reducing sugar the test tube colour will change from blue to a brick red in colour.
This is because the copper in benidicts solution is being reduced from +2 to +1 and thus forms that brick red colour in the solution.