A report on Tollens' reagent

Tollens' test for aldehyde: left side positive (silver mirror), right side negative
Ball-and-stick model of the diamminesilver(I) complex

Chemical reagent used to distinguish between aldehydes and ketones along with some alpha-hydroxy ketones which can tautomerize into aldehydes.

- Tollens' reagent
Tollens' test for aldehyde: left side positive (silver mirror), right side negative

10 related topics with Alpha

Overall
Aldehyde structure

Aldehyde

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Aldehyde is an organic compound containing a functional group with the structure R\sCH\dO.

Aldehyde is an organic compound containing a functional group with the structure R\sCH\dO.

Aldehyde structure
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In this test, an aldehyde is treated with Tollens' reagent, which is prepared by adding a drop of sodium hydroxide solution into silver nitrate solution to give a precipitate of silver(I) oxide, and then adding just enough dilute ammonia solution to redissolve the precipitate in aqueous ammonia to produce [Ag(NH3)2]+ complex.

On the left, the solution in the absence of reducing sugars. On the right, copper oxide, which would appear in the bottom of the solution if reducing sugars are present.

Fehling's solution

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On the left, the solution in the absence of reducing sugars. On the right, copper oxide, which would appear in the bottom of the solution if reducing sugars are present.

Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functional groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test.

Ketone group

Ketone

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Functional group with the structure R2C=O, where R can be a variety of carbon-containing substituents.

Functional group with the structure R2C=O, where R can be a variety of carbon-containing substituents.

Ketone group
Representative ketones, from the left: acetone, a common solvent; oxaloacetate, an intermediate in the metabolism of sugars; acetylacetone in its (mono) enol form (the enol highlighted in blue); cyclohexanone, precursor to nylon; muscone, an animal scent; and tetracycline, an antibiotic.
Keto-enol tautomerism. 1 is the keto form; 2 is the enol.
The Haller-Bauer reaction occurs between a non-enolizable ketone and a strong amide base. In this prototypical example involving benzophenone, the tetrahedral intermediate expels phenyl anion to give benzamide and benzene as the organic products

Ketones may be distinguished from aldehydes by giving a negative result with Tollens' reagent or with Fehling's solution.

Reactants, such as sulfur (pictured), are the starting materials that are used in chemical reactions.

Reagent

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Substance or compound added to a system to cause a chemical reaction, or test if one occurs.

Substance or compound added to a system to cause a chemical reaction, or test if one occurs.

Reactants, such as sulfur (pictured), are the starting materials that are used in chemical reactions.

Examples include Fehling's reagent, Millon's reagent, and Tollens' reagent.

Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+

Ammonia

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Compound of nitrogen and hydrogen with the formula NH3.

Compound of nitrogen and hydrogen with the formula NH3.

Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+
Ball-and-stick model of the tetraamminediaquacopper(II) cation, [Cu(NH3)4(H2O)2](2+)
Jabir ibn Hayyan
This high-pressure reactor was built in 1921 by BASF in Ludwigshafen and was re-erected on the premises of the University of Karlsruhe in Germany.
A train carrying Anhydrous Ammonia.
Liquid ammonia bottle
Household ammonia
Ammoniacal Gas Engine Streetcar in New Orleans drawn by Alfred Waud in 1871.
The X-15 aircraft used ammonia as one component fuel of its rocket engine
Anti-meth sign on tank of anhydrous ammonia, Otley, Iowa. Anhydrous ammonia is a common farm fertilizer that is also a critical ingredient in making methamphetamine. In 2005, Iowa used grant money to give out thousands of locks to prevent criminals from getting into the tanks.
The world's longest ammonia pipeline (roughly 2400 km long), running from the TogliattiAzot plant in Russia to Odessa in Ukraine
Hydrochloric acid sample releasing HCl fumes, which are reacting with ammonia fumes to produce a white smoke of ammonium chloride.
Production trend of ammonia between 1947 and 2007
Main symptoms of hyperammonemia (ammonia reaching toxic concentrations).
Ammonia occurs in the atmospheres of the outer giant planets such as Jupiter (0.026% ammonia), Saturn (0.012% ammonia), and in the atmospheres and ices of Uranus and Neptune.

Diamminesilver(I) ([Ag(NH3)2]+) is the active species in Tollens' reagent.

A 3D model of ethyne (acetylene), the simplest alkyne

Alkyne

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Alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond.

Alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond.

A 3D model of ethyne (acetylene), the simplest alkyne
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Thus, few drops of diamminesilver(I) hydroxide (Ag(NH3)2OH) reacts with terminal alkynes signaled by formation of a white precipitate of the silver acetylide.

Silver(I) oxide produced by reacting lithium hydroxide with a very dilute silver nitrate solution

Silver oxide

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Chemical compound with the formula Ag2O.

Chemical compound with the formula Ag2O.

Silver(I) oxide produced by reacting lithium hydroxide with a very dilute silver nitrate solution

It is soluble in ammonia solution, producing active compound of Tollens' reagent.

Ammonia solution

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Solution of ammonia in water.

Solution of ammonia in water.

Ammonia solution can dissolve silver oxide residues, such as that formed from Tollens' reagent.

Mutarotation: -glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other. The epimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.

Glucose

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Simple sugar with the molecular formula C6H12O6.

Simple sugar with the molecular formula C6H12O6.

Mutarotation: -glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other. The epimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.
Glucose can exist in both a straight-chain and ring form.
Widely proposed arrow-pushing mechanism for acid-catalyzed dynamic equilibrium between the α- and β- anomers of D-glucopyranose
Glucose-Fructose-Mannose-isomerisation
Glucose metabolism and various forms of it in the process.Glucose-containing compounds and isomeric forms are digested and taken up by the body in the intestines, including starch, glycogen, disaccharides and monosaccharides.Glucose is stored in mainly the liver and muscles as glycogen. It is distributed and used in tissues as free glucose.
Diagram showing the possible intermediates in glucose degradation; Metabolic pathways orange: glycolysis, green: Entner-Doudoroff pathway, phosphorylating, yellow: Entner-Doudoroff pathway, non-phosphorylating
Glucose, 5% solution for infusions
Glucose tablets
Relative sweetness of various sugars in comparison with sucrose

In the Tollens test, after addition of ammoniacal AgNO3 to the sample solution, glucose reduces Ag+ to elemental silver.

Bernhard Tollens

Bernhard Tollens

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German chemist.

German chemist.

Bernhard Tollens

It was during this final time in Göttingen that he started his work on carbohydrates, which yielded structures of several sugars, the Tollens' reagent, and most of his publications.