0
What else can I help you with?
What substrate gives a positive reaction for benedicts reagent?
Reduction of Benedict's reagent occurs with reducing sugars such as glucose, fructose, and galactose, giving a positive test result. This test is used to detect the presence of reducing sugars in various food products.
What is the difference between Benedict's Reagent and Biuret Reagent?
Benedicts reagent is used to check reducing sugars , it need hat to work and gives red color when positive ,. While biuret reagent is for proteins .there is no need to use heat and gives purple , violet color when positive ..
Why would glucose give positive result upon prolonged heating with seliwanoff's reagent?
Glucose gives a positive result with Seliwanoff's reagent upon prolonged heating because it is a reducing sugar that can reduce the reagent, leading to the formation of a cherry-red complex. This occurs due to the dehydration of glucose under acidic conditions, producing furfural, which then reacts with the reagent. The prolonged heating enhances this reaction, resulting in the characteristic color change indicative of a positive result.
When does a spray of diphenylamine reagent on TLC gives blue coloration?
Diphenylamine is a reagent for DNA.
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.
Why fructose gives positive tollen reagent test?
Only aldehydes give a positive Tollens test. However, under the strongly basic conditions of the test, alpha-hydroxy ketones can isomerize to aldehydes, so they will also give a positive Tollens test. Fructose is an alpha-hydroxy ketone.
What substances give a positive tollens test?
When adding the aldehyde or ketone to Tollens' reagent, the test tube is put in a warm water bath. If the reactant under test is an aldehyde, Tollens' test results in a silver mirror. If the reactant is a ketone, it will not react because a ketone cannot be oxidized easily. A ketone has no available hydrogen atom on the carbonyl carbon that can be oxidized - unlike an aldehyde, which has this hydrogen atom.
Why does sucrose solution give a negative test with tollen's test?
A positive Tollen's test is given by compounds that have a free aldehyde or ketone functional group. Sucrose is a disaccharide composed of the monosaccharides glucose and fructose. In sucrose, the components glucose and fructose are linked via an ether bond between C1 (carbon with aldehyde group) on the glucosyl subunit and C2 (carbon with ketone group) on the fructosyl unit. The bond is called a glycosidic linkage. In other words, in sucrose there is no free aldehyde or ketone functional group. Hence sucrose will not answer Tollen's test.
What reaction occurs when benzil gives tollens test?
Benzil does not react with Tollens reagent because it does not contain aldehyde or ketone functional groups. Tollens reagent is a silver mirror test used for the detection of aldehydes in a sample by the reduction of silver ions to metallic silver. Benzil, being a diketone, does not undergo this reaction.
What substrate gives a positive reaction for benedicts reagent?
Reduction of Benedict's reagent occurs with reducing sugars such as glucose, fructose, and galactose, giving a positive test result. This test is used to detect the presence of reducing sugars in various food products.
Why sucrose does not give a positive Benedict's test but hydrolyzed sucrose does give a positive beneditcts test?
Sucrose is formed from glucose and fructose.Sucrose is formed from glucose and fructose. Glucose and fructose gives positive test for benedict becuz both of them are reducing sugars whereas sucrose is not a reducing sugar so it gives negative test for benedict. On prolonged heating,sucrose will form glucose and fructose (reducing sugars)which ultimately gives a positive result .
What is the difference between Benedict's Reagent and Biuret Reagent?
Benedicts reagent is used to check reducing sugars , it need hat to work and gives red color when positive ,. While biuret reagent is for proteins .there is no need to use heat and gives purple , violet color when positive ..
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 does fructose give a positive Benedicts test?
Benedict's test detects the presense of the aldehyde group. Fructose is a ketose rather than an aldose, but it's converted to glucose or mannose (both of which are aldoses) by the base in Benedict's reagent. All monosaccharides give a positive Benedict's test because they're all either aldoses or alpha-hydroxy ketoses that get transformed into aldoses. Sucrose does not, because while it contains fructose and glucose, both of which do test postive, the saccharides in sucrose are "locked" into hemiacetal form and cannot undergo ring opening to expose an aldehyde group. (It's a very weak lock; dilute acid ... like, say, lemon juice ... will hydrolyse the saccharide linkage and allow the hemiacetal rings to open.)
Which sugar gives a negative reaction to Benedict reagent?
Sucrose gives a negative reaction to the Benedict's reagent test because it is a non-reducing sugar. Benedict's reagent is used to test for the presence of reducing sugars, which have the ability to reduce the copper ions in the reagent. Since sucrose does not have this ability, it does not give a positive reaction.
Why would glucose give positive result upon prolonged heating with seliwanoff's reagent?
Glucose gives a positive result with Seliwanoff's reagent upon prolonged heating because it is a reducing sugar that can reduce the reagent, leading to the formation of a cherry-red complex. This occurs due to the dehydration of glucose under acidic conditions, producing furfural, which then reacts with the reagent. The prolonged heating enhances this reaction, resulting in the characteristic color change indicative of a positive result.
When does a spray of diphenylamine reagent on TLC gives blue coloration?
Diphenylamine is a reagent for DNA.
