Glucose oxidizes very quickly, and creates a silver mirror layer between the glucose solution and the Tollens' reagent. This is because of how the ketose reacts and reduces the silver molecules in Tollen's reagent.
RCHO + 2[Ag(NH3)2] + 2OH- -----> RCOOH + 2Ag0 + 4NH3 + H2O
glucose give silver mirror
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. ;-)
You are not supposed to use buret reagent to detect sugar carbohydrates in a solution. Buret reagent is used to detect proteins. Try using iodine ( I2KI)
breaks down sucrose into glucose and fructose
Glucose meter and test stripe
no negative
The sucrose does not react with Fehling's reagent. Sucrose is a disaccharide of glucose and fructose. Most disaccharides are reducing sugars, sucrose is a notable exception, for it is a non-reducing sugar. The anomeric carbon of glucose is involved in the glucose- fructose bond and hence is not free to form the aldehyde in solution.
The Fehling A solution contain copper sulfate.The Fehling B solution contain sodium potassium tartrate and sodium hydroxide.
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.
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. ;-)
You are not supposed to use buret reagent to detect sugar carbohydrates in a solution. Buret reagent is used to detect proteins. Try using iodine ( I2KI)
breaks down sucrose into glucose and fructose
Glucose meter and test stripe
Benedicts reagent tests for reducing sugars, so the question is, is raffinose a reducing sugar. Raffinose is a trisaccharide made up of glucose, fructose and galactose. It is not a reducing sugar because all of its anomeric carbons are bonded, so it will not react with benedicts reagent.
no negative
It tests for glucose.
glucose
the sugar glucose