Barfoed's tests for carbohidrate

Barfoed's tests:

Barfoed's Test is a chemical test used for detecting the presence of monosaccharides. It was invented by Danish chemist Christen Thomsen Barfoed and is primarily used in botany. The test is similar to the reaction of Fehling's solution to aldehydes.

Barfoed's reagent:

Barfoed's reagent consists of a 0.33 molar solution of neutral copper acetate in 1% acetic acid solution. The reagent does not keep well and it is therefore advisable to make it up when it is actually required.

How to perform the test:

One ml of a sample solution is placed in a test tube. Three ml of Barfoed's reagent (a solution of cupric acetate and acetic acid) is added. The solution is then heated in a boiling water bath for three minutes.


Reactions:

It is based on the ), reduction of copper(II) acetate to copper(I) oxide (Cu2O) which forms a brick-red precipitate.
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 may interfere.