The mechanism of the silver mirror reaction, the principle of the silver mirror reaction

The principle is the weak oxidation of silver ammonia solution.

In this test, other reducing substances can be used instead of acetaldehyde, such as glucose (similar to acetaldehyde, but also has an aldehyde group).

Formaldehyde (which can be seen as having two aldehyde groups) is oxidized to ammonium carbonate (NH4)2CO3.

C6H12O6+2AG(NH3)2OH ---heated in water bath)C6H11O5CoonH4+3NH3 +2AG+H2O

Reaction equation for glucose.

To reflect the internal structure of glucose and the breakage of bonds:

CH2OH-CHOH-CHOH-CHOH-CHOH-CHOH-CH+2AG(NH3)2OH (water bath heating).

ch2oh-choh-choh-choh-choh-coonh4+2ag↓+3nh3↑+h2o

For organic reactions, electron transfer is generally not studied, but structural changes are studied.

The silver mirror reaction can be thought of as the cleavage of the C—H bond of the aldehyde group, and the addition of an oxygen atom becomes a carboxyl group. The aldehyde group is oxidized.

Therefore, organic redox reactions are not analyzed from the perspective of electron gain and loss. Rather, it is analyzed from the perspective of oxygen and hydrogen gain and loss. Oxygen or dehydrogenation is an oxidation reaction, and deoxygenation or hydrogen is a reduction reaction.

The reducing properties of the aldehyde group and the oxidation of the silver ammonia solution.

The principle of the silver mirror reaction is the chemical reaction in which the solution of the silver compound is reduced to metallic silver, and the resulting metallic silver is attached to the inner wall of the container and is as bright as a mirror, so it is called the silver mirror reaction. A common silver mirror reaction is the reduction of silver ammonia complexes to silver by aldehyde compounds, and the oxidation of aldehydes to the corresponding carboxylic acid ions, but in addition, some silver compounds can also be reduced by reducing agents to produce silver mirrors.

The silver mirror reaction is a qualitative experiment used to detect aldehydes and reducing sugars, mainly used to detect the presence of aldehyde groups. This experiment is simple to operate, the phenomenon is obvious, and it is easy to observe. This reaction is used in the laboratory to identify compounds containing aldehyde groups.

In industry, this reaction is used to coat glass with silver mirrors and thermos flasks. This experiment is mainly used in the mirror industry, and is also used for the concentration identification of organic raw materials in the industrial laboratory.

Silver Mirror Reaction:

2% silver nitrate, 4% sodium hydroxide, dilute ammonia.

1.Caustic washing of test tubes (heating).

ml of 2% silver nitrate, add dilute ammonia until the precipitate is just dissolved, then drop in 1-2 drops of 4% sodium hydroxide, shake well, add 2-3 drops of 40% acetaldehyde, shake for 1 minute to make it yellow, and let it stand to get the silver mirror. Acetaldehyde reacts with copper hydroxide: it depends on the alkalinity, and has nothing to do with whether it is new or not.

Under strong alkaline conditions, the complexes of copper ions can react at the appropriate temperature.

Silver mirror reaction principle: silver ammonia gravel ions have a certain oxidation, and aldehyde groups are reducible, therefore, it is the redox reaction between the aldehyde group and the silver ammonia gravel ions, the silver ammonia gravel ions are reduced to metallic silver, and the aldehyde group is oxidized to carboxyl groups. The silver ammonia solution is to react in an alkaline solution environment.

Take the reaction of acetaldehyde and silver ammonia solution as an example:

ch3cho+2ag(nh3)2+ 2oh-→ch3coonh4+2ag↓+3nh3+h2o

The silver mirror reaction is a reaction in which the silver-ammonia complex ammonia-silver complex (also known as Tolen's reagent) is reduced to silver by aldehydes and oxidized to the corresponding carboxylate ions.

c6h12o6+2[ag(nh3)2]oh=c5h11o5coonh4+3nh3+2ag↓+h2o

ch2oh-choh-choh-choh-choh-cho+2[ag(nh3)2]oh=ch2oh-choh-choh-choh-choh-coonh4+2ag↓+3nh3+h2o

Since the solution of silverification is reduced to metallic silver, the reaction is known as the silver mirror reaction. Because the metal silver produced is attached to the inner wall of the test tube, it is as bright as a mirror, so it is called the silver mirror reaction.

1. Silver ammonia solution reacts with acetaldehyde.

CH3CHO+2[AG(NH3)2]OH=CH3CoonH4+2AG +3NH3+H2O (Ethersilver is reduced and acetaldehyde is oxidized).

2. Silver ammonia solution reacts with formaldehyde.

hcho + 4[ag(nh3)2]oh = (nh4)2co3 + 4ag↓+ 6nh3 +2h2o

3. Silver ammonia solution reacts with glucose.

C6H12O6+2[AG(NH3)2]OH=C5H11O5CoonH4+3NH3+2AG +H2O (because ammonia is easily soluble in water, the upward arrow is not marked).

Aldehyde-containing substances such as glucose are oxidized by a silver ammonia solution to precipitate silver.