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Why does starch produce a negative result with Benedict's reagent?
Wiki User
∙ 14y ago
Benedict test have a negative result in glycogen because glycogen is a polysaccharide. Benedict test is meant for testing reducing sugars. It can also give positive results in the case of disaccharide or monosaccharide.
Wiki User
∙ 15y ago
Wiki User
∙ 14y agoBecause it is a so-called nonreducing sugar in neutral or alkaline solution.
In acidic solution however (e.g. in sugar containing limonades),
the nonreducing di-saccharide sucrose is quit easily turned ('hydrolysed' or split) into
the two mono- saccharides glucose and fructose, which are in fact (in this test) reducing.
- The aldose glucose is a straight forward reducing sugar, so positively detected by B's test reagent.
- The ketose fructose is not strictly a reducingsugar (it is an beta-hydroxy-ketone, not an aldehyde), but it becomes reducing thus giving a positive test.
This is because this 'alpha-hydroxy-ketone' is converted to the aldoses: glucose and mannose, by the alkaline solution of the Benedict's test (called 'keto-enol'-tautomerisation).
Wiki User
∙ 15y agosucrose is a glucose polymer that doesn't have the free carbonly group to react with the benedicts solution.
Wiki User
∙ 14y agoBenedict's Reagent tests only for 'reducing sugars' (monosaccharides), starch is a polysaccharide
Wiki User
∙ 12y agoBenedict's solution reacts with simple sugars like glucose, which are monosaccharides. Sucrose is not a simple sugar, it is a disaccharide.
Wiki User
∙ 15y agosolution remain blue
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An unknown sample is tested with both biuret reagent and benedicts reagent both test result in a blue color what has been learned and why are these called negative results?
That the unknown sample is not a monosaccharide and is does not contain peptide bonds (is not a protein). This is because they both produced negative results because Biuret tests positive in solutions that contain peptide bonds and will turn a violet color. Benedict reagent reacts to monosaccharides and will turn green-reddish orange when a monosaccharide is present. Neither of these things happened so the results are negative.
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A negative result for the spores stain indicate that the gram-negative organism is present. A positive result for a spore stain indicates that a gram positive organism is present.
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Does using benedicts reagent on honey produce a positive result?
yes
Will hydrolysed dextrine give positive response to Benedict test?
Yes, it should. Benedicts test will be positive for reducing sugars, and since glucose is such a sugar, and would be a product of dextrin hydrolysis, you should get a positive result with Benedicts reagent.
When glycogen is added to benedicts reagent why would it remains blue?
Although glycogen is a carbohydrate, it is classified under POLYSACCHARIDES which are non-reducing sugars. Benedict's reagent is used to test for the presence of non-reducing sugars. The positive result for this is a brick-red precipitate or solution. It remained blue (which is negative) due to fact that ALL POLYSACCHARIDES (such as glycogen) ARE NON-REDUCING SUGARS > I'm a Nursing Student. >M.J.T.M.E.
An unknown sample is tested with both biuret reagent and benedicts reagent both test result in a blue color what has been learned and why are these called negative results?
That the unknown sample is not a monosaccharide and is does not contain peptide bonds (is not a protein). This is because they both produced negative results because Biuret tests positive in solutions that contain peptide bonds and will turn a violet color. Benedict reagent reacts to monosaccharides and will turn green-reddish orange when a monosaccharide is present. Neither of these things happened so the results are negative.
What would the result of crackers in benedicts test?
Turns blue black
What is the reaction of propanol to lucas reagent?
2-Methyl-1-propanol is a primary alcohol and so will not react with Lucas reagent at room temperature.Cyclopentanol is a secondary alcohol and so will react with Lucas reagent in 3-5 minutes (solution turns cloudy). Cyclopentyl chloride is the result.1-Methylcyclopentanol is a tertiary alcohol and so will react immediately with Lucas reagent to produce turbidity. 1-Chloro-1-methylcyclopentanol is the result.
Why does sucrose not react to Benedicts when glucose and fructose its components do?
Fructose and glucose are joined by their glycosidic bond in such a way as to prevent the glucose isomerizing to aldehyde, or the fructose to alpha-hydroxy-ketone form. This stops it reacting to Benidict's reagent. However 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. ;-)
Effect of formaldehyde to schiff's reagent?
a mixture of formaldehyde and schiif's reagent will result to a purple solution
What solution is use to test starch?
Iodine-KI reagent. Add to the substance being tested directly. Result: If positive, Turns Blue/Black If negative, (absence of starch) Solution remains orange/yellow.
What If a material has dissolved in a solvent or reagent what does the result look like?
The solution must by homogeneous.
Are there any books named Love Has no Feelings?
A search on booksites Abe, Alibris and Amazon all produce a negative result for that title.
What is the result when albumin solution pepsin and HCl are mixed with biuret reagent?
The reagent turns pink due to the presence of broken amino acid chains of the albumin, a source of protein.
