In lab, we used Benedict’s reagent to test for one particular reducing sugar: glucose. Benedict’s reagent starts out aqua-blue. As it is heated in the presence of reducing sugars, it turns yellow to orange. The “hotter” the final color of the reagent, the higher the concentration of reducing sugar.
Which sugar gives positive Benedict’s test?
The reducing sugars that show positive results with benedict’s solution are glucose, fructose, maltose etc. The correct option is D i.e. sucrose. Additional Information: Sucrose is a disaccharide composed of two monosaccharide molecules that are glucose and fructose.
What is Benedict test for glucose?
Benedict’s Test is used to test for simple carbohydrates. The Benedict’s test identifies reducing sugars (monosaccharide’s and some disaccharides), which have free ketone or aldehyde functional groups. Benedict’s solution can be used to test for the presence of glucose in urine.
Why is Benedict not exclusive to glucose?
The Benedict test isn’t specific for glucose; it just tells you if an aldehyde is present. So it will also give a positive test for other reducing sugars. In short, any sugar* (*mono- or disaccharide) with a hemiacetal will also give a positive test, since these sugars are in equilibrium with an open-chain aldehyde.
Is Benedict test positive for fructose?
Because both the Tollens’ and Benedict’s reagents are basic solutions, ketoses (such as fructose) also give positive tests due to an equilibrium that exists between ketoses and aldoses in a reaction known as tautomerism.
Does lactose give a positive Benedict test?
Lactose, D-ribose, and D-glyceraldehyde would give a positive Benedict’s test. To be a reducing sugar, a disaccharide must contain an anomeric carbon atom that can open up to form an aldehyde functional group, as shown in this disaccharide (answers will vary).
Which compound does not give Benedict Test?
C6H5CHO is an aromatic aldehyde. It will not give Benedict test. Only aliphatic aldehyde give Benedict’s test.
Why sucrose gives a negative Benedict Test?
Sucrose contains two sugars (fructose and glucose) joined by their glycosidic bond in such a way as to prevent the glucose isomerizing to aldehyde, or the fructose to α-hydroxy-ketone form. Sucrose is thus a non-reducing sugar, which does not react with Benedict’s reagent.
Which sugar is not a reducing 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.
Why is Benedict Test semi quantitative?
As color of the obtained precipitate can be used to infer the quantity of sugar present in the solution, the test is semi-quantitative.
What colour is glucose?
Glucose forms white or colorless solids that are highly soluble in water and acetic acid but poorly soluble in methanol and ethanol.
What type of sugar is lactose?
Lactose is a sugar found in milk. It is a disaccharide made up of glucose and galactose units. It is broken down into the two parts by an enzyme called lactase. Once broken down, the simple sugars can be absorbed into the bloodstream.
Is lactose a reducing sugar?
For the same reason lactose is a reducing sugar. The free aldehyde formed by ring opening can react with Benedict’s solution. Thus, a solution of lactose contains both the α and β anomer at the “reducing end” of the disaccharide. Although the aglycone can be either α or β, the glycosidic bond is always β in lactose.