Why does benedict solution react with glucose

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.

Benedict's reagent can be prepared from sodium carbonate , sodium citrate and copper II sulfate. These are precipitated as red copper I oxide which is insoluble in water.

To test for the presence of monosaccharides and reducing disaccharide sugars in food, the food sample is dissolved in water, and a small amount of Benedict's reagent is added. The mixture is heated in a boiling water bath, and any precipitate formed is recorded as a positive result for the presence of reducing sugars in the food.

The common disacharrides lactose and maltose are directly detected by Benedict's reagent, because each contains a glucose with a free reducing aldehyde moiety, after isomerization. Sucrose table sugar contains two sugars fructose and glucose joined with by their glycosidic bond in such a way as to prevent the glucose isomerizing to aldehyde, or the fructose to alpha-hydroxy-ketone form. The result l had was a dark brown color.

What might be the cause of this result? So 2 ml would be 40 drops. What should the protocol say? There is one major problem in this writing…. Hydrogens are protons…often, having given away an electron, they acquire a positive charge. It is also quite difficult to clean any glassware after that mistake. Hydrogens are not electrons, they are protons and often have a positive charge. Is it possible that the sugars are reducing sugars because they accept hydrogens instead of give them up?

Save my name and email in this browser for the next time I comment. Following this condition, high amount of brick-red colour precipitate will be formed at the end of the test tube. Sometimes you will find small amounts of copper oxide along with brick-red precipitate. Another compound Sodium citrate complexes with the copper II ions to avoid degradation into copper I ions during storage.

Some complex type of carbohydrates like starch or amylum consisting of a large number of glucose monomer units joined by glycosidic bonds. Sucrose which is commonly known as table sugar contains two reducing sugars moieties fructose and glucose. These reducing sugar are joined by their glycosidic bond in such a way as to prevent the glucose isomerising to aldehyde, or the fructose to alpha-hydroxy-ketone form.

Sucrose is thus a non-reducing sugar which does not react with Benedict's reagent. Sucrose still indirectly can produce a positive result with Benedict's reagent if heated with dilute hydrochloric acid HCl prior to the test. The acidic conditions and heat break the glycosidic bond in sucrose through hydrolysis process. The products of hydrolysis process are reducing sugars glucose and fructose which can be detected by Benedict's reagent. To contact the author mail: articles worldofchemicals.

Stay updated with the latest chemical industry trends and innovations. Verification Code has been sent to. The color of the mixture will change accordingly resulting in precipitates, which indicates positive results.

The results of the test can be summarized in the table below [6 — 8]. Excess glucose can lead to diabetes. Glucose is called reducing sugar because it is capable of transferring hydrogen to other compounds.

Such a process is known as reduction or redox reaction. Your email address will not be published. Chemistry Learner It's all about Chemistry.