Sucrose is thus a non-reducing sugar, which does not react with Benedict's reagent. Sucrose indirectly produces a positive result with Benedict's reagent if heated with dilute hydrochloric acid prior to the test, although after this treatment it is no longer sucrose. Was this answer helpful?
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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.
Sucrose (table sugar) contains two sugars (fructose and glucose) joined by their glycosidic bond in such a way as to prevent the glucose undergoing isomerization to an aldehyde, or fructose to alpha-hydroxy-ketone form. Sucrose is thus a non-reducing sugar which does not react with Benedict's reagent.
It can be noted that Benedict's test can also be used to check for the presence of glucose in a urine sample. Since this test detects any aldehydes and α-hydroxy ketones and glucose is an aldose whose open-chain forms an aldehyde group, the test yields a positive result when glucose is present in the analyte.Mar 2, 2021
1 Benedict's solution will release carbon dioxide bubbles from sucrose but it cannot release carbon dioxide from glucose. 2 Benedict's solution turns orange in the presence of sucrose but remains blue in the presence of glucose.Dec 18, 2021
Benedict's test was performed on three carbohydrates, depicted from left to right: fructose, glucose, and sucrose. The solution containing sucrose remains blue because sucrose is a nonreducing sugar. These reactions have been used as simple and rapid diagnostic tests for the presence of glucose in blood or urine.Oct 26, 2016
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..Aug 8, 2012
Complex carbohydrates such as starches DO NOT react positive with the Benedict's test unless they are broken down through heating or digestion (try chewing crackers and then doing the test). Table sugar (disaccharide) is a non-reducing sugar and does also not react with the iodine or with the Benedict Reagent.Aug 15, 2019
4.4 Chemistry Sucrose is a non-reducing sugar and must first be hydrolyzed to its components, glucose and fructose, before it can be measured in this assay.
A blue-black color results if starch is present. If starch amylose is not present, then the color will stay orange or yellow. Starch amylopectin does not give the color, nor does cellulose, nor do disaccharides such as sucrose in sugar.
Sucrose is a non-reducing sugar because The two monosaccharide units are held together by a glycosidic linkage between C1 of α-glucose and C2 of β-fructose. Since the reducing groups of glucose and fructose are involved in glycosidic bond formation, sucrose is a non-reducing sugar.
The table sugar was negative for reducing sugars because it contains sucrose. Sucrose is a disaccharide made up of the monomers glucose and fructose with bond formations that reduce both ends of the sugar making the disaccharide a non-reducing sugar.
Why does a positive Benedict test result confirm that the unknown solution originally contained starch? A positive result indicates simple sugars (maltose) that result from starch being digested by amylase. A substance that is the smallest unit of a category of substances.
Starch is composed of linear chain of glucose (amylose) and branched chain of glucose (amylopectin). Amylopectin reacts with iodine to give positive blue-black color. In case of sucrose, amylopectin is absent and glucose moiety is also not exposed, so, result will be negative.
In case of disaccharide, it is negative for tehalose and sucrose as they both are non- reducing sugars. Rest, it is positive for all sugars.