Fehling's solution is a solution used to differentiate between water soluble aldehyde and ketone functional groups, although ketose monosaccharides (such as fructose) will also test positive, due to conversion to aldoses by the base in the reagent ^[1]. For this reason, Fehling's reagent is sometimes referred to as a general test for monosaccharides. Making a saline water solution by dissolving table salt (NaCl) in water This article is about chemical solutions. ... An aldehyde. ... Ketone group A ketone (pronounced as key tone) is either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains this functional group. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Fructose, an example of a ketose. ... Monosaccharides are the simplest form of carbohydrates. ... Fructose (or levulose) is a simple sugar (monosaccharide) found in many foods and is one of the three most important blood sugars along with glucose and galactose. ...

Fehling's is used to test for aldoses and ketoses, although simpler aldehydes such as formic acid (methanoic acid) also give a positive Fehling's test result, as it does with Tollens' test, Benedict's test. and many more aldehyde tests. Formic acid (systematically called methanoic acid) is the simplest carboxylic acid. ... Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+ Tollens reagent is usually ammoniacal silver nitrate, but can also be other things, as long as there is an aqueous diamminesilver(I) complex. ... Benedicts Reagent (also called Benedicts solution or Benedicts test) is a reagent named after an American chemist, Stanley Rossiter Benedict. ...

To carry out the test The substance to be tested is heated together with Fehling's solution; a red precipitate indicates the presence of an aldehyde. Ketones (except alpha-hydroxy-ketones) do not react. An example for its use is to screen for glucose in urine, thus detecting diabetes. It was developed by German chemist Hermann von Fehling. Precipitation is the condensation of a solid from a solution during a chemical reaction. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... This article is about the urine of animals generally. ... This article is about the disease that features high blood sugar. ... Hermann von Fehling (9 June 1812 - 1 July 1885) was a German chemist, famous as the developer of Fehlings solution used for estimation of sugar. ...

Fehling's solution is always made just prior to the test. It is comprised of equal parts of the following solutions:

• 69.28 grams copper(II) sulphate pentahydrate dissolved in 1 litre of distilled water (Fehling's solution A)
• 346 grams Rochelle salt (potassium sodium tartrate tetrahydrate) and 120 grams sodium hydroxide in 1 litre of distilled water (Fehling's Solution B)

This article or section cites very few or no references or sources. ... Bottle for Distilled water in the Real Farmacia in Madrid. ... Potassium sodium tartrate is a double salt first prepared (in about 1675) by an apothecary, Pierre Seignette, of La Rochelle, France. ... Flash point Non-flammable. ...

Fehling test

An aldehyde is first added to the Fehling solution and the mixture is heated. Aldehyde oxidizes to acid and red precipitates of cuprous oxide are formed The cupric ion is complexed with the tartrate ion. Contact with an aldehyde group reduces it to a cuprous ion, which then precipitates as red Cu₂O (copper(I) oxide). Ketones (except alpha hydroxy ketones such as are present in ketoses and other metabolites) and aromatic aldehydes do not respond to the Fehling test. Image File history File links Fehling_test. ... Copper(I) Oxide or Cuprous oxide (Cu2O) is an oxide of copper. ... A complex in chemistry is a reversible association of molecules, atoms, or ions through weak non-covalent chemical bonds. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ...

Fehling's solution in the present day is often replaced by Benedict's solution. Benedicts reagent (also called Benedicts solution or Benedicts Test) is a reagent used as a test for the presence of reducing sugars (such as glucose, lactose, and fructose, but not sucrose) in a solution. ...

Note: Fehling's solution can only be used to test for aliphatic aldehydes, whereas tollen's reagent can be used to test for both aliphatic and aromatic aldehydes

Images

The aldehyde form of glucose Image File history File links Download high-resolution version (1100x728, 162 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Glucose ...

[CuII(tartrate)2]4− complex

Crystal structure of the copper(I) oxide precipitate

References

1. ^ http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-Fehling-e.htm