Monday, January 23, 2012

Benedict reagent Benedict's solution Benedict's test

Benedict reagent Benedict's solution Benedict's test

What is Benedict's Reagent?

Benedict's reagent also called Benedict's solution or Benedict's test) is a chemical reagent.
Benedict's reagent is used as a test for the presence of reducing sugars. This includes all monosaccharides and the disaccharides, lactose and maltose.

 Even more generally, Benedict's test will detect the presence of aldehydes (except aromatic ones), and alpha-hydroxy-ketones, including those that occur in certain ketoses. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha-hydroxy-ketone, and gives a positive test because it is converted to the aldoses glucose and mannose by the base in the reagent.

The copper sulphate in Benedict's solution reacts with reducing sugars.
One litre of Benedict's reagent can be prepared from 100 g of anhydrous sodium carbonate, 173 g of sodium citrate and 17.3 g of copper(II) sulfate pentahydrate.
It is often used in place of Fehling's solution.

Benedict's reagent contains blue copper(II) ions (Cu2+) which are reduced to copper(I) ions (Cu+). These are precipitated as red copper(I) oxide which is insoluble in water.

This reagent is used to test for sugars. 
The disacarides (Sucrose, Lactose and Maltose) doesn't give a positive result with just the reagent, but there is a round about method I'm going to show in a future video

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