Limitations of Tollens’ Test

What is Tollens’ Test?

Tollens test, also known as the silver mirror test, is a chemical test used to detect the presence of aldehydes in a given alpha-hydroxyorganic compound. When an aldehyde is present, it will react with Tollens’ reagent to produce a silver mirror on the inside of a test tube. This test is often used in qualitative organic chemistry to distinguish between aldehydes and ketones because ketones do not give a positive Tollens test (except alpha-hydroxy ketone)....

Tollens Reagent

Tollens’ reagent is often referred to as “Tollens’ reagent” or “Ammoniacal Silver Nitrate solution.” It is named after Bernhard Tollens, the German chemist who developed the reagent in the late 19th century. The reagent is used for the qualitative detection of aldehydes. Its formula is ([Ag(NH3)2]+...

Reaction of Tollens Test

The Tollens test, also called as the Silver Mirror test, is a test which is used to detect the presence of aldehydes in a given organic compound. This test is based on the reaction between Tollens’ reagent and aldehydes, which results in the formation of a Silver Mirror on the inner surface of a test tube. This test is widely used in qualitative organic chemistry to identify and characterize aldehydes in various chemical reactions. Tollens’ reagent should be prepared and used with caution, as it contains ammonia and silver ions, which can be hazardous....

Principle of Tollens’ Test

The Tollens’ reagent is the solution of alkaline silver nitrate [(AgNO3)] combined with aqueous ammonia solution (NH4OH), leading to the development of a complex. Silver nitrate in water produces a silver-aqua complex, in which water acts as a ligand. Hydroxide ions convert the aqua complexes into silver oxides (Ag2O). The [Ag(NH3)2]+ complex is formed when silver oxide develops a brown precipitate, which would be subsequently dissolved by aqueous ammonia. The complex subsequently forms a carboxylic acid by oxidizing the aldehyde group in a given compound. The silver ions in the reagent will be converted to metallic silver. A silver mirror forms on the bottom side of a test tube as silver ions are reduced to metallic silver. A terminal hydroxy ketone produces a positive Tollens test because this Tollen’s reagent will convert the ketone into an aldehyde....

Mechanism of Tollens Test

When an aldehyde is introduced to Tollens’ reagent, it acts as a reducing agent. Aldehydes have a hydrogen atom on the carbonyl group (C=O) that can be oxidized. The aldehyde is oxidized by the silver ions in the reagent as follows:...

Uses of Tollens Test

The Tollens test is mainly use in the following cases:...

Limitations of Tollens’ Test

There are some sugars which can be isomerized under alkaline circumstances, certain carbohydrates without an aldehyde group may give positive Tollens’ test. Silver nitrate is a hazardous chemical so when it comes in contact with skin or clothing, the color of the same will disappear. So it is recommended to wear gloves and also ammonia fumes must not be inhaled....

Sample Questions on Tollens Test

Question 1: Can Tollens’ Test be performed in a beaker or conical flask?...

FAQs on Tollens Reagent

What is Tollens Test for Aldehyde?...