Barfoed's Test is a chemical test

Chemical test

In chemistry, a chemical test is a qualitative or quantitative procedure designed to prove the existence of, or to quantify, a chemical compound or chemical group with the aid of a specific reagent...

 used for detecting the presence of monosaccharide

Monosaccharide

Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...

s. It is based on the reduction of copper(II) acetate

Copper(II) acetate

Copper acetate, also referred to as cupric acetate, is the chemical compound with the formula Cu2 where OAc- is acetate . The hydrated derivative, which contains one molecule of water for each Cu atom, is available commercially. Anhydrous Cu2 is a dark green crystalline solid, whereas Cu22 is...

 to copper(I) oxide

Copper(I) oxide

Copper oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper. This red-coloured solid is a component of some antifouling paints. The compound can appear either yellow or red, depending on the size of the particles, but both forms...

 (Cu₂O), which forms a brick-red precipitate.

RCHO + 2Cu²⁺ + 2H₂O → RCOOH + Cu₂O↓ + 4H⁺

(Disaccharide

Disaccharide

A disaccharide or biose is the carbohydrate formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides form an aqueous solution when dissolved in water...

s may also react, but the reaction is much slower.) The aldehyde group of the monosaccharide which normally forms a cyclic hemiacetal

Hemiacetal

Hemiacetals and hemiketals are compounds that are derived from aldehydes and ketones respectively. The Greek word hèmi means half...

 is oxidized to the carboxylate

Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

. A number of other substances, including sodium chloride, may interfere.

It was invented by Danish chemist Christen Thomsen Barfoed

Christen Thomsen Barfoed

Christen Thomsen Barfoed was a Danish chemist who devised a way to detect monosaccharide sugars in a solution, now known as the Barfoed's test. Barfoed is also credited with having introduced systematic chemical analyses in Danish agricultural sciences.-References:...

 and is primarily used in botany

Botany

Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

.

The test is similar to the reaction of Fehling's solution

Fehling's solution

Fehling's solution is a chemical test used to differentiate between water-soluble aldehyde and ketone functional groups, and as a test for monosaccharides. The test was developed by German chemist Hermann von Fehling in 1849.-Laboratory preparation:...

 to aldehydes.

Composition

Barfoed's reagent consists of a 0.33 molar solution of neutral copper acetate in 1% acetic acid

Acetic acid

Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

solution. The reagent does not keep well and it is therefore advisable to make it up when it is actually required.