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Trehalose does not give a positive test with Seliwanoff's reagent because trehalose is a non-reducing sugar. Seliwanoff's reagent reacts with ketoses to form a red color, but since trehalose contains two glucose units linked by an α,α-1,1-glycosidic bond, it does not have a free ketone or aldehyde group necessary for the reaction with Seliwanoff's reagent.
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Principle in seliwanoff's test?
Seliwanoff's test is used to distinguish between aldoses and ketoses. The principle behind the test is that aldoses react with resorcinol in a hot acid medium to produce a cherry red color, while ketoses do not give a positive result. This is due to the structural differences between aldoses and ketoses affecting their reactivity with resorcinol.
Why seliwanoff's test is positive only for keto sugars?
Seliwanoff's test is positive only for keto sugars because they contain a ketone group in their structure that reacts with the reagents in the test to form a pink color. Aldose sugars do not contain this ketone group and therefore do not yield a positive result in the Seliwanoff's test.
Can Seliwanoff's test be used to distinguish sucrose from fructose?
Yes, fructose is a ketose, for which Seliwanoff's test is most sensitive. Sucrose is neither entirely a ketose nor an aldose, but is a mixture of both. It will react, but more slowly, producing a much lighter pinkish color.
Why resorcinol is used as a reagent in test in seliwanoff test?
Resorcinol is used as the complexing agent to provide the color reaction, although the exact nature of the colored product is not known. Since resorcinol favors electrophilic aromatic substitution, the reaction may be similar to the Molisch Test.
What is the aim of using a strong acid in seliwanoff's test?
to hydrolysis polysaccharide and oligasaccharide, ketose yields simpler sugar followed by furfural
Sucrose gives seliwanoff's test why not trihalose?
Sucrose gives a positive Seliwanoff's test because it is a disaccharide composed of glucose and fructose, which can be dehydrated to form a furfural derivative that reacts with the test reagent to produce a cherry-red color. In contrast, trehalose, which is a disaccharide made of two glucose units linked by an α,α-1,1-glycosidic bond, does not readily undergo this dehydration reaction under the conditions of the test, resulting in a negative reaction. Therefore, only sucrose shows a positive result in the Seliwanoff's test.
When did Theodor Seliwanoff die?
Theodor Seliwanoff died in 1895.
When was Theodor Seliwanoff born?
Theodor Seliwanoff was born in 1817.
What is the result of the seliwanoff test if the solution contains both fructsoe and glucose?
the glucose would remain yellow which is the initial colour of the seliwanoff's reagent. the fructose however being a ketose forms a furfural because of the HCL present in the seliwanoff reagent and reacts with the resorcinol to give a red cherry or pink colour.
Why seliwanoff's test gives a color upon long heating a solution of glucose?
Seliwanoff's test is specific for detecting ketoses, such as fructose. Upon long heating, fructose in the presence of concentrated acid will dehydrate to form furfural derivatives, giving a red color. Glucose, a aldose sugar, does not undergo this reaction and will not give a color with Seliwanoff's test.
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Does galactose give a positive test for thee Seliwanoff's test?
Galactose does not give a positive test for Seliwanoff's test. This test is used to differentiate between aldose and ketose sugars, with ketoses producing a rapid red color upon heating with the reagent. Since galactose is an aldose, it would not produce the characteristic reaction indicative of ketoses.
What is the significance of seliwanoff's test?
Seliwanoff's test is used to distinguish between ketoses and aldoses in carbohydrates. It is based on the reaction of ketoses with resorcinol in concentrated acid to produce a cherry-red color, while aldoses do not give this color change. This test is particularly useful in differentiating fructose (a ketose) from glucose (an aldose).
Principle in seliwanoff's test?
Seliwanoff's test is used to distinguish between aldoses and ketoses. The principle behind the test is that aldoses react with resorcinol in a hot acid medium to produce a cherry red color, while ketoses do not give a positive result. This is due to the structural differences between aldoses and ketoses affecting their reactivity with resorcinol.
Why seliwanoff's test is positive only for keto sugars?
Seliwanoff's test is positive only for keto sugars because they contain a ketone group in their structure that reacts with the reagents in the test to form a pink color. Aldose sugars do not contain this ketone group and therefore do not yield a positive result in the Seliwanoff's test.
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What color will sucrose turn when mix with seliwanoff reagent?
the solution turns to deep red...
