Chemical properties of aldehydes: silver mirror reaction. What is the silver mirror reaction
Silver oxide dissolves to form a complex compound - diammine silver(I) hydroxide OH
when an aldehyde is added to which an oxidation-reduction reaction occurs to form metallic silver:
If the reaction is carried out in a vessel with clean and smooth walls, then the silver precipitates in the form of a thin film, forming a mirror surface. In the presence of the slightest contamination, silver is released in the form of a gray loose sediment.
The "silver mirror" reaction can be used as a qualitative reaction for aldehydes. Thus, the “silver mirror” reaction can be used to distinguish between glucose and fructose. Glucose is an aldose (contains an aldehyde group in an open form), and fructose is a ketose (contains a keto group in an open form). Therefore, glucose gives a “silver mirror” reaction, but fructose does not.
Literature
- Nekrasov B.V. Fundamentals of general chemistry. - 3rd ed., rev. and additional - M.: “Chemistry”, 1973. - T. 2. - 688 p.
- Nesmeyanov A. N., Nesmeyanov N. A. The beginnings of organic chemistry. In 2 volumes. - 2nd ed., trans. - M.: “Chemistry”, 1974. - T. 1. - 624 p.
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Let's start with the fact that each class of organic substances has a certain reaction with the help of which its representatives can be distinguished from other substances. The school chemistry course involves studying all high-quality reagents for the main classes of organic substances.
Aldehydes: structural features
Representatives of this class are derivatives of saturated hydrocarbons in which the radical is connected to an aldehyde group. Ketones are isomers of aldehydes. Their similarity lies in their belonging to the class of carbonyl compounds. When performing a task that involves isolating an aldehyde in a mixture, a “silver mirror” reaction will be required. Let us analyze the features of this chemical transformation, as well as the conditions for its implementation. The silver mirror reaction is the reduction process of silver metal from silver diamine(1) hydroxide. In a simplified form, it is possible to write this complex compound in the simplified form of silver oxide (1).
Separation of carbonyl compounds
To form a complex compound, silver oxide is dissolved in ammonia. Considering that the process is a reversible reaction, the silver mirror reaction is performed with a freshly prepared ammonia solution of silver oxide (1). When a complex compound of argentum is mixed with an aldehyde, a redox reaction occurs. The completion of the process is indicated by the precipitation of metallic silver. When the interaction of ethanal and an ammonia solution of silver oxide is carried out correctly, the formation of a silver coating is observed on the walls of the test tube. It was the visual effect that gave this interaction the name “silver mirror.”
Determination of carbohydrates
The reaction of a silver mirror is qualitative to an aldehyde group, so in organic chemistry courses it is also mentioned as a way to recognize carbohydrates such as glucose. Considering the specific structure of this substance, which exhibits the properties of an aldehyde-alcohol, thanks to the “silver mirror” reaction, it is possible to distinguish glucose from fructose. Thus, this is not only a qualitative reaction to aldehydes, but also a way to recognize many other classes of organic substances.
Practical application of the “silver mirror”
It would seem, what difficulties may arise with the interaction of aldehydes and an ammonia solution of silver oxide? You just need to purchase silver oxide, stock up on ammonia and select an aldehyde - and you can safely begin the experiment. But such a primitive approach will not lead the researcher to the desired result. Instead of the expected mirror surface on the walls of the test tube, you will see (in best case scenario) dark brown silver suspension.
The essence of interaction
A high-quality reaction to silver implies adherence to a certain algorithm of actions. Often, even when signs of a mirror layer appear, its quality clearly leaves much to be desired. What are the reasons for such a failure? Is it possible to avoid them? Among the many problems that can lead to undesirable results, there are two main ones:
- violation of the conditions for chemical interaction;
- poor surface preparation for silvering.
During the interaction of the starting substances in the solution, silver cations are formed, combining with the aldehyde group, ultimately forming colloidal small particles of silver. These grains are able to adhere to glass, but can be preserved in solution as a silver suspension. For particle adhesion to occur noble metal with glass, a uniform and durable layer is formed, it is important to pre-degrease the glass. Only if there is a perfectly clean initial surface of the test tube can one count on the formation of a uniform silver layer.
Possible problems
The main contaminant of glassware is greasy deposits, which must be removed. An alkali solution, as well as a hot chrome mixture, will help solve the problem. Next, the test tube is washed with distilled water. If there is no alkali, you can use a synthetic dishwashing detergent. After degreasing is completed, the glass is washed with a solution of tin chloride and rinsed with water. Distilled water is used to prepare solutions. If it is not available, you can use rainwater. Glucose and formaldehyde are used as reducing agents that allow the precipitation of a pure substance from a solution. With aldehyde it is difficult to count on obtaining a high-quality silver coating, but a monosaccharide (glucose) gives a uniform and durable silver layer on the surface of the mirror.
Conclusion
To silver glass, it is advisable to use silver nitrate. Alkali and ammonia solution are added to the solution of this salt. The condition for a complete reaction and deposition of silver on glass is the creation of an alkaline environment. But if there is an excess of this reagent, side effects. Depending on the chosen experimental technique, a high-quality reaction is obtained by heating. Coloring the solution in Brown color indicates the formation of tiny colloidal particles of silver. Next, a mirror coating appears on the surface of the glass. If the process is successful, the metal layer will be smooth and durable.
Conducting a lesson in the elective course “Experiment in Organic Chemistry”
Lesson research
Practical work No. 3 “Silver mirror reaction”
Subject: Study of the interaction of organic compounds of various classes with silver (I) compounds.
The purpose of the lesson:
General education
Investigate the interaction of classes of organic compounds with silver compounds, find out the reason for the selectivity of this interaction.
Developmental
Development of thinking skills, comparison, analysis, synthesis of cognitive skills. The ability to pose and ask a question, formulate a problem, and draw conclusions; improving independent behavior skills.
Didactic
To develop competencies in the field of independent cognitive activity, teamwork skills, the ability to see a problem and outline ways to solve it.
Educational
Formation of ideological thinking, expansion of horizons, formation of a positive attitude towards the study of the subject, the habit of helping comrades, a conscientious attitude towards the task being performed, developing demands on oneself and comrades.
Methods: research, work with educational literature, partially search, laboratory work, group.
Equipment: On the students’ desks are instruments and reagents for conducting laboratory work “The “Silver Mirror” Reaction”, task cards, and a presentation for the lesson.
During the classes
“The time for miracles has passed, and we
You have to look for reasons
Everything that happens in the world"
W. Shakespeare
(slide No. 1)
Teacher's opening speech : Anyone who has an idea about the science of chemistry knows that a chemical experiment is an integral part of it. Entertaining experiments And practical lessons help develop chemical thinking and promote the assimilation of chemistry. The elective course “Studying organic chemistry through a system of experimental problems” is designed for 17 hours 12 - practical work. Most practical work is carried out in small groups of students. The course work is structured as follows. Students receive assignments on the topic of the upcoming practical work. At home, they get acquainted with theoretical material and study the content of the work itself.
Today we are holding practical work No. 3 (see title above)
(slide No. 2)
The purpose of this work: to experimentally study the interaction of classes of organic compounds with silver compounds, to find out the reason for the selectivity of this interaction, to consolidate the practical skills necessary in the activities of an experimenter.
(slide No. 3)
Students received a preliminary assignment for the lesson.
Teacher : The reaction of the silver compound is called the “silver mirror reaction.” Tell us the story of how you got this mirror.
1 student : The story of getting the mirror. Mirrors... ThisThis is a completely everyday thing in our lives. Few people know that mirrors appeared long before our era. At first they were metal plates made of gold, silver, copper or bronze, polished to a shine. The production of modern mirrors (on glass) was started in 1858 by the German chemist Justus Liebig. For this purpose, he used the ability of silver cations to form numerous complex compounds.One day, after washing the inner surface of the flask with a soda solution, and then with water, ethyl alcohol and diethyl ether, Liebig poured a little diluted formaldehyde into it - a 10% formaldehyde solution. Then, adding a solution of silver ammonia compound to the formaldehyde, he carefully heated the flask.After a few minutes, the flask became mirror-like.
The complex silver-containing cation is reduced to metal (silver), and formaldehyde is oxidized to formic acid HCOOH. Subsequently, instead of formaldehyde, Justus Liebig used glucose to obtain the “silver mirror”.
Teacher : tell us about the history of the production of Tollens' reagent, which is widely used in analytical chemistry.
2 student: History of obtaining Tollens' reagent. In 1881, the German chemist Bernhard Christian Tollens proposed using a silver complex compound to detect compounds with an aldehyde group in solution. When an aqueous solution of ammonia is added to a solution of silver nitrate, a gray-black precipitate of oxide precipitates, since silver hydroxide does not exist under normal conditions.
2AgNO 3 + 2NH 4 OH → Ag 2 O + 2NH 4 NO 3 + H 2 O
Silver oxide dissolves in excess ammonia water and forms a complex unity.
Ag 2 O + 4NH 4 OH → 2 OH +3H 2 O
The resulting colorless solution is called Tollens' reagent.
2. Main part
“There is no way to become a chemist,
Without seeing the practice itself
and without taking up chemical operations"
M.V. Lomonosov
(slide No. 4)
A) Role-playing game: The class is a research laboratory that begins its work to study the interaction of various classes of organic compounds with silver (I) compounds. Students are divided into three creative groups. Each creative group has an information department and a chemical laboratory. Groups receive theoretical and practical tasks and work (5-7 minutes). Along with the task, instructions for completing the experiment are given. (slide No. 5)
Task 1 creative group
Task 2 creative group
Does it interact? Why?
Information Department: What classes of organic compounds do the issued substances belong to? What functional groups do they have?
Task 3 creative group
Information Department: What classes of organic compounds do the issued substances belong to? What functional groups do they have?
(slide No. 6)
"The thinking mind does not feel happy,
until it is possible to connect disparate facts together,
observed by him"
D. Hevesy.
(slide No. 7)
B) Discussion of the reports of each group
Teacher: And now the creative groups must report on the work done. A student in a chemical laboratory talks about his observations that occur during an experiment, drawing a conclusion about the class with which the silver compound interacts. At this time, the student who makes up the information department goes out and writes down the reaction equation for the interaction of an organic substance with silver (I) oxide, highlighting the functional group of each class.
The reaction record is checked on the corresponding slide No. 8, 9,10
The general conclusion is formulated that Tollens' reagent (silver compound (I)) is qualitative for the aldehyde group, which is found in aldehydes, glucose and formic acid. (slide No. 11)
The lesson is summarized.
"The joy of seeing and understanding
there is the most beautiful gift"
A. Einstein
(slide No. 12)
The silver mirror reaction is used to make mirrors, silvering decorations and Christmas tree decorations.
Qualitative analysis of substances is an important topic in the study of organic chemistry. Knowledge of it helps in their work not only chemists, but also doctors, ecologists, biologists, epidemiologists, pharmacists, and food industry workers.
Conclusion. We sum up the results and give ratings. Thank you for your attention!
Instructions for laboratory experiment
The “silver mirror” reaction
Pour 2 ml of a 1% solution of silver nitrate AgNO3 into a test tube and add 10% ammonia water NH4OH in small portions until the resulting silver oxide precipitate is completely dissolved. (Or use ready-made Tollens reagent)
Add 1 ml to the resulting solution. test substance. Heat the contents by rotating the test tube around the flame, heating the walls rather than the bottom. Hold the test tube vertically.
1. What do you observe in the test tube?
2. Why does the glass surface become mirror-like?
3. Write the equation for the reaction.
Instructions for laboratory experiment
The “silver mirror” reaction
Pour 2 ml of a 1% solution of silver nitrate AgNO3 into a test tube and add 10% ammonia water NH4OH in small portions until the resulting silver oxide precipitate is completely dissolved. (Or use ready-made Tollens reagent)
Add 1 ml to the resulting solution. test substance. Heat the contents by rotating the test tube around the flame, heating the walls rather than the bottom. Hold the test tube vertically.
1. What do you observe in the test tube?
2. Why does the glass surface become mirror-like?
3. Write the equation for the reaction.
Instructions for laboratory experiment
The “silver mirror” reaction
Pour 2 ml of a 1% solution of silver nitrate AgNO3 into a test tube and add 10% ammonia water NH4OH in small portions until the resulting silver oxide precipitate is completely dissolved. (Or use ready-made Tollens reagent)
Add 1 ml to the resulting solution. test substance. Heat the contents by rotating the test tube around the flame, heating the walls rather than the bottom. Hold the test tube vertically.
1. What do you observe in the test tube?
2. Why does the glass surface become mirror-like?
3. Write the equation for the reaction.
Task 1 creative group
Chemical laboratory: The test tubes contain two organic substances: glucose and ethanol. Carry out the reaction of these substances with an ammonia solution of silver (I) oxide. Which substance does not interact? Why?
Information Department: What classes of organic compounds do the issued substances belong to? What functional groups do they have?
Task 2 creative group
Chemical laboratory: The test tubes contain two organic substances: formaldehyde (formalin, methanal) and acetic acid, carry out the reaction of these substances with an ammonia solution of silver (I) oxide. Which of the substances is not interacts? Why?
Information Department: What classes of organic compounds do the issued substances belong to? What functional groups do they have?
Task 3 creative group
Chemical laboratory: There are two organic substances in the test tubes: formic acid and glycerol, carry out the reaction of these substances with an ammonia solution of silver (I) oxide. Which substance does not interact? Why?
Information Department: What classes of organic compounds do the issued substances belong to? What functional groups do they have?
The "silver mirror" reaction is the reduction reaction of silver in an ammonia solution of silver oxide (Tollens' reagent). In an aqueous solution of ammonia, silver oxide forms a complex compound - silver diamine hydroxide OH
Ag 2 O + 4 NH 4 OH => 2 OH + H 2 O
when exposed to an aldehyde, a redox reaction occurs with the formation of an ammonium salt:
R-CH=O + 2 OH => RCOONH 4 + 2 Ag +3 NH 3 + H 2 O
A silver mirror is formed when reducing silver is deposited on the smooth walls of a vessel from not too concentrated solutions. The slightest impurities prevent the reducing silver from “clinging” to the glass and cause it to precipitate as a loose precipitate.
Ketones are much more difficult to oxidize than aldehydes, so ketones do not give a “silver mirror” reaction, so the “silver mirror” reaction can be used as a qualitative reaction for aldehydes. Thus, the “silver mirror” reaction can be used to distinguish between glucose and fructose. Glucose is an aldose (contains an aldehyde group in an open form), and fructose is a ketose (contains a keto group in an open form). Therefore, glucose gives a “silver mirror” reaction, but fructose does not.
HOCH 2 (CHOH) 4 HC=O + 2 OH => HOCH 2 (CHOH) 4 COOH + 2 Ag +3 NH 3 + H 2 O
42. Disaccharides. Reducing and non-reducing disaccharides. Sucrose. Maltose. Cellulose.Lactose Disaccharides
Disaccharides are carbohydrates that, when heated with water in the presence of mineral acids or under the influence of enzymes, undergo hydrolysis, splitting into two molecules of monosaccharides.
The most widespread disaccharide is sucrose(cane or beet sugar). It is obtained from sugar cane or sugar beets. Milk contains 5% lactose - milk sugar. Maltose Contained in germinating grains and formed during the hydrolysis of grain starch. Cellobiose is an intermediate product in the enzymatic hydrolysis of cellulose.
Structure. A disaccharide molecule consists of two monosaccharide molecules connected by a glycosidic bond. Depending on which carbon atoms are involved in the formation of the glycosidic bond, the disaccharide molecule may or may not contain a free carbonyl group.
Disaccharides can be divided into two groups: non-restorative and restorative. Non-reducing sugars do not have an OH group at any anomeric center, while reducing sugars have a free OH group at the anomeric center.
Non-reducing sugars are called glycosyl glycosides; reducing - glycosyl-glycoses.
Maltose– a reducing disaccharide formed during the enzymatic hydrolysis of starch. Maltose consists of two D-glucose residues connected by a glycosidic bond at positions.
Sucrose consists of glucose and fructose residues connected by a 1,2-glycosidic bond. In sucrose, the hemiacetal hydroxyl groups of both monosaccharide molecules participate in the formation of a glycosidic bond, as a result of which sucrose is a non-reducing sugar.
Chemical properties of disaccharides:
1) the ability to hydrolyze: under the action of an acid or an appropriate enzyme, the glycosidic bond is broken and two monosaccharides are formed;
2) are oxidized by copper, silver, mercury ions, form osazones and enter into all reactions characteristic of compounds containing free carbonyl groups;
3) disaccharides can be oxidized to carbon dioxide and water. Under the action of yeast enzymes, sucrose and maltose produce ethanol, but lactose remains unchanged.
Lactose is a disaccharide, that is, it consists of two elementary sugars, which represent the minimum structural units. Any complex carbohydrate (for example, starch, lactose or cellulose) breaks down into monosaccharides, which are absorbed into the blood and used by the body for various needs. Since lactose consists of two monosaccharides (glucose and galactose), when it enters the human body under the influence of digestive enzymes, the entire compound breaks down into them. As a result of the breakdown of lactose into glucose and galactose, the latter are absorbed into the blood and utilized by the cells of the human body. The enzyme that breaks down lactose into galactose and glucose in the digestive tract is called lactase.
43.Polysaccharides. Starch, glycogen, fiber, high molecular weight polysaccharides Polysaccharides- the general name for a class of complex high-molecular carbohydrates, the molecules of which consist of tens, hundreds or thousands of monomers - monosaccharides.
Polysaccharides are necessary for the life of animal and plant organisms. They are one of the main sources of energy generated as a result of the body's metabolism. They take part in immune processes, provide cell adhesion in tissues, and constitute the bulk of organic matter in the biosphere.
· starch is the main polysaccharide deposited as an energy reserve in plant organisms;
· glycogen is a polysaccharide deposited as an energy reserve in the cells of animal organisms, but is found in small quantities in the tissues of plants and fungi;
· cellulose is the main structural polysaccharide of plant cell walls;
Starch (C6H10O5)n– a polysaccharide that consists of two fractions: 25% linear amylose and 75% branched amylopectin. It is formed in light in plants during photosynthesis. This substance is White powder, which does not dissolve in cold water, forming a suspension. After the suspension has settled, a white sediment is deposited at the bottom of the container, and the water can be easily drained. After drying, starch regains all its properties.
In hot water, this substance forms a colloidal solution - this is a sticky liquid, which is also called starch paste and is often used in everyday life as an adhesive. The preparation of jelly and some desserts is also based on this property. Starch is a chemically inert substance. In order for it to react, catalysts must be involved in this process. The use of this substance is based on its physical and chemical properties. Thus, starch and its derivatives are often used in the food, textile and paper industries. And for living organisms it plays an important role. To use this organic substance for industrial purposes, it is subjected to chemical action. Starch hydrolysis is an exchange process between ions of a substance and water, which can be enzymatic or acidic. Chemical hydrolysis of starch is a catalytic reaction, as it occurs when heated in the presence of inorganic acids. During this chemical reaction, glucose is formed, which can be expressed by the equation: (C6H10O5)n + nH2O + (cat. H2SO4 + t°) = nC6H12O6.
But recently, enzymatic hydrolysis of starch has become very popular. Using special technologies, ethyl alcohol, molasses and glucose are obtained from it in the same way as through chemical hydrolysis. The advantage of this process is that starch-containing plants, for example, rye, potatoes, corn, rice and some others, are taken as the starting material. These sources, moreover, contain amylolytic enzymes, which are used in the hydrolysis process. For example, such enzymes are isoamylase, pullulanase, and glucolinase. Enzymes are natural catalysts that speed up chemical reactions. Schematically, the process of starch breakdown under the action of enzymes looks like this: starch → soluble starch (amylose) → oligosaccharides (dextrins) → disaccharide (maltose = malt) → α-glucose. It can also be expressed by the equation: (C6H10O5)n + nH2O + (cat. enzyme) = nC6H12O6 You can clearly see that chemical hydrolysis has occurred by conducting an experiment. Boil a mixture of starch paste and sulfuric acid. We check whether hydrolysis has occurred - drop iodine. If the reaction is negative, that is, there is no blue or purple color, then hydrolysis has occurred. Now we prove that the product of hydrolysis is glucose. Add alkali and copper (II) sulfate (CuSO4) to the resulting solution. The copper hydroxide precipitate does not precipitate; the solution acquires a bright blue color. We heat it up and see the formation of a terracotta (brick) colored precipitate - this means that the solution contains glucose, which was formed during hydrolysis. Enzymatic hydrolysis of starch also occurs in the human body. This process is very important, since it produces carbohydrates, in particular glucose. It is oxidized in every cell of the body, forming water and carbon dioxide, while releasing energy that is necessary for the normal functioning of the body. Hydrolysis of starch with the help of enzymes begins in the oral cavity when chewing food. Human saliva contains an enzyme - amylase, under the influence of which starch is broken down into simpler components - dextrins. A person can even feel this process. After all, if you chew bread for a long time, a sweetish taste appears in your mouth, which indicates that the process of starch hydrolysis has begun. Excess glucose, which is formed during hydrolysis, is deposited in the liver in the form of a reserve nutrient - glycogen.
6 45. The concept of pectin substances. The concept of modified starch and hemicellulose.
Pectic substances are complex polysaccharides - polygalacturonides, consisting of b-D-galacturonic acid residues connected by 1,4-bonds.
There are three types of pectin substances:
Protopectin - water insoluble component cell wall;
Pectin is a water-soluble polymer of galacturonic acid containing methyl ester bonds;
Pectic acid is a water-soluble polymer of galacturonic acid, free from methyl ester bonds. Pectic acid consists of long chains of galacturonic acids, capable of forming a solid pectin gel after treatment with calcium salts.
Laboratory work No. 5
Propertiescarbohydrates
Experiment 1. Reaction of a silver mirror is a recovery reaction silver from ammonia solution silver oxide (Tollens reagent).
In aqueous solution ammonia silver oxide dissolves to form a complex compound - diammine silver(I) hydroxide OH
when added to which aldehyde a redox reaction occurs to form metallic silver:
If the reaction is carried out in a vessel with clean and smooth walls, then the silver precipitates in the form of a thin film, forming a mirror surface.
In the presence of the slightest contamination, silver is released in the form of a gray loose sediment.
The "silver mirror" reaction can be used as a qualitative reaction for aldehydes. Thus, the “silver mirror” reaction can be used as a distinctive one between glucose And fructose. Glucose is an aldose (contains an aldehyde group in an open form), and fructose is a ketose (contains a keto group in an open form). Therefore, glucose gives a “silver mirror” reaction, but fructose does not. But if an alkaline medium is present in the solution, then ketoses isomerize into aldoses and also give positive reactions with an ammonia solution silver oxide (Tollens reagent).
Qualitative reaction of glucose with an ammonia solution of silver oxide. The presence of an aldehyde group in glucose can be proven using an ammonia solution of silver oxide. Add glucose solution to the ammonia solution of silver oxide and heat the mixture in a water bath. Soon metallic silver begins to deposit on the walls of the flask. This reaction is called the silver mirror reaction. It is used as a quality compound for the discovery of aldehydes. The aldehyde group of glucose is oxidized to a carboxyl group. Glucose is converted into gluconic acid.
CH 2 HE – (SNON) 4 – SLEEP +Ag 2 O= CH 2 HE – (SNON) 4 – COOH + 2Ag↓
The order of work.
2 ml is poured into two test tubes. ammonia solution of silver oxide. Add 2 ml to one of them. 1% glucose solution, the other - fructose. Both test tubes are boiling.
An ammonia solution of silver oxide hydrate is obtained by reacting silver nitrate with sodium hydroxide and ammonium hydroxide:
AgNO3+ NaOH → AgOH↓+ NaNO3,
AgOH + 2 NH4 OH→[ Ag(NH3)2] OH + H2O,
ammonia solution
OH + 3 H2→ Ag2O + 4 NH4 OH.
Principle of the method. A mirror is formed on the walls of the test tube with glucose as a result of the release of metallic silver.
Design of the work: Write the conclusion, as well as the course and equations of the reaction in a notebook.
Experiment 3. Qualitative reaction to fructose
Principle of the method. When heating a sample containing fructose in the presence resorcinol And of hydrochloric acid up to 80 o C after some time a bright red color appears in the test tube with fructose.
When heating a sample containing fructose in the presence resorcinol And of hydrochloric acid a cherry-red color appears. The sample is also applicable to detect other ketosis. Aldose under the same conditions, they interact more slowly and give a pale pink color or do not interact at all. Open F. F. Selivanov in 1887. Used for urine analysis. The test is positive for fructosuria of metabolic or transport origin. In 13% of cases, the test is positive with a food load of fruits and honey. Chem. formula fructose – C 6 H 12 O 6
Cyclic formula of fructose
Acyclic form 
fructose
Painted connection
R- residues
hydroxymethylfurfural
The order of work.
2 ml are poured into two test tubes: into one - a 1% glucose solution, into the other - a 1% fructose solution. 2 ml of Selivanov’s reagent are added to both test tubes: 0.05 g of resorcinol is dissolved in 100 ml of 20% hydrochloric acid. Both test tubes are carefully heated to 80 o C (before boiling). A red color appears.
Conclusions: the results of the experiment and the reaction equation are written down in a notebook.
