BARFOED’S TESTPost Laboratory Report

Group 4

A. What is the Principle involved in the Barfoed’s Test?

When barfoed reagent mix with solution of monosaccharide or disaccharide, and heated in boiling water bath, they react and crystal precipitate is formed.

Copper acetate which is present in barfoed’s reagent convert to copper oxide and give brick red precipitate when react with monosaccharide or disaccharides.

Monosaccharde react fast while disaccharide react slowly.

B. Purpose of this test Barfoed's test is a chemical test used

for detecting the presence of monosaccharides.

C. What components make up the Barfoed’s reagent? State the function of each component/

The reagent is prepared by dissolving copper acetate monohydrate and glacial acetic acid in water. Acetic Acid present in the reagent hydrolyzes disacchrides to monosacchrides. Reducing monosaccharides are oxidized by the copper ion in the solution to form a carboxylic acid and a reddish precipitate of copper (I).

D. Provide the type equation used in the test.

Hi Whiteboard

E. Show the sample equation involved in the reaction between Barfoed’s reagent and the sample which gave a positive result:

  RCHO + 2Cu2+ + 2H2O → RCOOH + Cu2O↓ + 4H+ Reducing monosaccharides are oxidized by the

copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes. Reducing disaccharides undergo the same reaction, but do so at a slower rate.

F. Provide an Explanation (POSITIVE)Monosaccharides

The commonly occurring monosaccharides includes glucose, fructose, galactose, ribose, etc.

The two monosaccharides combine together to form disaccharides which include sucrose, lactose and maltoses

Result of the Test: Glucose: With brick red

precipitate =POSITIVE Sucrose: No brick red

precipitate =NEGATIVE Lactose: No brick red

precipitate =NEGATIVE

Positive: Monosaccharides

Barfoed's test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu2O), which forms a brick-red precipitate.[1][2]

When barfoed reagent mix with solution of monosaccharide, and heated in boiling water bath, they react and crystal precipitate is formed. Copper acetate which is present in barfoed’s reagent convert to copper oxide and give brick red precipitate when react with monosaccharide.

Negative: Disaccharides (Disaccharides may also react, but the

reaction is much slower.) The aldehyde group of the monosaccharide which normally forms a cyclic hemiacetal is oxidized to the carboxylate. A number of other substances, including sodium chloride,[3] may interfere.

G. Why is heating of the mixture limited to three minutes only?

H. How does this test compare with Fehling’s and Benedict’s Test? Which is more accurate?

all of the test is used as a general test for detecting reducing sugars. but they are different in the reagents used to detect the sugars.

Shows positive test for: Reducing monosaccharides