Tests Benedict

Reducing sugar (Section 25.6) A sugar that reduces silver ion in the Tollens test or cupric ion in the Fehling or Benedict tests. 

In another dry-reagent configuration in Diasti (Ames Co.) the o-tolidine in the second stage of the reaction is replaced by potassium iodide, which is oxidized in the presence of peroxidase to form free iodine. Newer test strips contain hexokinase in place of glucose oxidase. A very sensitive spot test for Benedict-positive compounds is described, which uses 2,2 -bicinchoninate as a chromogen. This test is 10 000 times more sensitive than the classical Benedict test. 

Chen Q, Klemm N, Duncan G, and Jeng G (1990) Sensitive Benedict Test. Analyst 115(1) 109-110. 

Benedict solution Aqueous solution of Na2C03, CuSO, and sodium citrate used for testing for reducing agents, particularly sugars, which give red-yellow colours or precipitates. 

Aromatic aldehydes react with the dimedone reagent (Section 111,70,2). All aromatic aldehydes (i) reduce ammoniacal silver nitrate solution and (ii) restore the colour of SchifiF s reagent many react with sodium bisulphite solution. They do not, in general, reduce Fehling s solution or Benedict s solution. Unlike aliphatic aldehydes, they usually undergo the Cannizzaro reaction (see Section IV,123) under the influence of sodium hydroxide solution. For full experimental details of the above tests, see under Ali-phalic Aldehydes, Section 111,70. They are easily oxidised by dilute alkaline permanganate solution at the ordinary temperature after removal of the manganese dioxide by sulphur dioxide or by sodium bisulphite, the acid can be obtained by acidification of the solution. 

The formation of a red precipitate of copper(I) oxide by reduction of Cu(II) is taken as a positive test for an aldehyde Carbohydrates that give positive tests with Benedict s reagent are termed reducing sugars... 

Benedict s reagent is the key material in a test kit avail able from drugstores that permits individuals to mom tor the glucose levels in their urine... 

Which of the following would be expected to give a positiv test with Benedicts reagent Why ... 

Oxidation with Benedict s reagent (Section 25 19) Sugars that con tain a free hemiacetal function are called reducing sugars They react with copper(ll) sulfate in a sodium citrate/sodium carbonate buffer (Benedict s reagent) to form a red precipitate of copper(l) oxide Used as a qualitative test for reducing sugars... 

Benedicts reagent (Section 25 19) A solution containing the citrate complex of CUSO4 It is used to test for the presence of reducing sugars... 

Oxidation of the aldehyde group of an aldose to form a carboxyUc acid or carboxyUc acid anion is often used analytically to determine the amount of reducing sugar. The Benedict and Fehling methods measure the amount of reducing sugar present in a fluid. In these reactions, the oxidant, Cu ", is reduced to Cu". Cu" precipitates as CU2O, which can be measured in a variety of ways. In the ToUens test, Ag" is reduced to Ag. ... 

What can be learned about sugars by performing the Benedict s test ... 

Place 5 mL of the solutions of glucose, fructose, sucrose, and starch into the appropriately labeled test tube, numbered 1 through 4. Add 4 mL of Benedict s solution to each test tube and shake each solution until thoroughly mixed. Place each test tube in the boiling-water bath and heat for... 

After 5 minutes of heating, remove the test tubes and place them in the test-tube rack to cool. Record your observations in Data Table 1. Note any color changes or precipitate that formed. Benedict s solution contains an oxidizing agent... 

Data Table 3 Benedict s Test of Hydrolyzed Solutions ... 

Thinking Critically Were reducing sugars detected in the hydrolyzed starch solution using the Benedict s test Was this expected ... 

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