chem stories

Definition reducing sugar
If a sugar contains aldehyde groups that are oxidised to carboxylic acids, then that sugar is classified as a reducing sugar. It is called a reducing sugar because it reduces the number of chemicals present in its structure through oxidation.

Examples
Reducing sugars include glucose, fructose, glyceraldehyde, lactose, arabinose and maltose.

Reducing Capabilities
Reducing capability is defined by the presence of potential aldehyde or ketone group, anomeric carbons found in sugars, which determine a substance's ability to lose or gain electrons to form new or more stable solutions or its reaction to other substances.

Testing
Benedict and Fehling's reagent are two solutions used to determine the reducing capability of a sugar. These solutions are used to determine the presence of free aldehyde or ketone group in sugars.

Non-Reducing Sugar
The reason that sucrose is a non-reducing sugar is that it has no free aldehyde or keto group. Additionally, its anomeric carbon is not free and can't easily open up its structure to react with other molecules.


SUCROSE
The common name for sucrose is table sugar. Just as the name implies, sucrose is used throughout the world as a sweetener for cooking, baking and sweetening edibles. Sucrose is commonly made by refining plant matter, such as sugarcane or sugar beets. In its most commonly used form, it is a white, orderless powder that is sweet to the taste. Although sucrose is a disaccharide, it is not a reducing sugar.

Sucrose is the technical term for table sugar such as cane sugar or white sugar. It is composed of the combination of one glucose molecule and one fructose molecule.

Formation
The process starts with a condensation reaction, a process involving the release of water. This process is followed by the formation of a glycosidic bond between two available and appropriate monosaccharide molecules, creating disaccharides like sucrose.

Properties
Sucrose is soluble in water but its molecules are too big to pass through the cell membrane during diffusion. It can only be broken down through a hydrolysis reaction, a reverse condensation reaction.

Disaccharide
Sucrose is a complex carbohydrate known as a disaccharide, meaning made up of two simple carbohydrates or monosaccharides. The monosaccharides that form sucrose are glucose and fructose. Disaccharide is the most common form of sugar that is found in nature. It results from the combination or reaction of two simple sugars (monosaccharides). It has two types, the reducing and non-reducing sugar. Sucrose is a classic example of a non-reducing sugar.


Significance
Although both glucose and fructose are reducing sugars, sucrose is not because it does not contain anomeric hydroxyl groups, and does not reduce the chemicals present in its structure through oxidation.

Identification
It is possible to test a substance such as sucrose for the qualities that make it a reducing sugar using Fehling's solution, a mixture of copper sulfate, distilled water, Rochelle salt and sodium hydroxide. In the presence of reducing sugars, the copper sulfate in the solution will oxidize and turn red.






Read more: Why Is Sucrose a Non-Reducing Sugar? | eHow.com http://www.ehow.com/facts_5882980_sucrose-non_reducing-sugar_.html#ixzz15o22o2m6