1. Pentin-1 reacts with an ammonia solution of silver oxide (precipitates):
HCºС-CH 2 -CH 2 -CH 3 + OH → AgСºС-CH 2 -CH 2 -CH 3 + 2NH 3 + H 2 O
2. Cyclopentene decolorizes bromine water:
3. Cyclopentane does not react with either bromine water or ammonia solution of silver oxide.
Example 3 Five numbered tubes contain hexene, formic acid methyl ester, ethanol, acetic acid, and an aqueous solution of phenol.
It has been established that under the action of metallic sodium on substances from test tubes 2, 4, 5 gas is released. Substances from test tubes 3, 5 react with bromine water; with an ammonia solution of silver oxide - substances from test tubes 1 and 4. Substances from 1, 4, 5 test tubes react with an aqueous solution of sodium hydroxide.
Set the contents of the numbered tubes.
Solution. For recognition, we will compile Table 2 and immediately make a reservation that the condition of this problem does not take into account the possibility of a number of interactions, for example, methyl formate with bromine water, phenol with a solution of diammine silver hydroxide. The sign - denotes the absence of interaction, the sign + - the ongoing chemical reaction.
table 2
Interactions of analytes with proposed reagents
Example 4 In six numbered tubes there are solutions: isopropyl alcohol, sodium bicarbonate, acetic acid, aniline hydrochloric acid, glycerin, protein. How to determine in which test tube each of the substances is located?
Solution. .
When bromine water is added to solutions in numbered test tubes, a precipitate forms in a test tube with aniline hydrochloride as a result of its interaction with bromine water. The identified solution of aniline hydrochloric acid acts on the remaining five solutions. Carbon dioxide is released in a test tube with sodium bicarbonate solution. The established sodium bicarbonate solution acts on the remaining four solutions. In a test tube with acetic acid, carbon dioxide is released. The remaining three solutions are treated with a solution of copper (II) sulfate, which causes a precipitate to form as a result of protein denaturation. To identify glycerol, copper (II) hydroxide is prepared from solutions of copper (II) sulfate and sodium hydroxide. Copper(II) hydroxide is added to one of the remaining two solutions. In the case of dissolution of copper (II) hydroxide with the formation of a clear solution of bright blue copper glycerate, glycerin is identified. The remaining solution is an isopropyl alcohol solution.
Example 5. Seven numbered tubes contain solutions of the following organic compounds: aminoacetic acid, phenol, isopropyl alcohol, glycerin, trichloroacetic acid, aniline hydrochloride, glucose. Using as reagents only solutions of the following inorganic substances: 2% copper (II) sulfate solution, 5% iron (III) chloride solution, 10% sodium hydroxide solution and 5% sodium carbonate solution, determine the organic substances contained in each tube.
Solution. We immediately warn that here we offer a verbal explanation of the identification of substances .
When a solution of iron (III) chloride is added to solutions taken from numbered test tubes, a red color is formed with aminoacetic acid and a violet color with phenol. When a sodium carbonate solution is added to the samples of solutions taken from the remaining five test tubes, carbon dioxide is released in the case of trichloroacetic acid and aniline hydrochloride, with the rest of the substances there is no reaction. Aniline hydrochloride can be distinguished from trichloroacetic acid by adding sodium hydroxide to them. At the same time, an emulsion of aniline in water is formed in a test tube with aniline hydrochloride, and no visible changes are observed in a test tube with trichloroacetic acid. Determination of isopropyl alcohol, glycerol and glucose is carried out as follows. In a separate test tube, by mixing 4 drops of 2% copper (II) sulfate solution and 3 ml of 10% sodium hydroxide solution, a blue precipitate of copper (II) hydroxide is obtained, which is divided into three parts.
A few drops of isopropyl alcohol, glycerin and glucose are added separately to each part. In a test tube with the addition of isopropyl alcohol, no changes are observed; in test tubes with the addition of glycerol and glucose, the precipitate dissolves with the formation of complex compounds of an intense blue color. The resulting complex compounds can be distinguished by heating the upper part of the solutions in test tubes on a burner or spirit lamp until boiling begins. In this case, no color change will be observed in the test tube with glycerin, and a yellow precipitate of copper (I) hydroxide appears in the upper part of the glucose solution, turning into a red precipitate of copper (I) oxide, the lower part of the liquid, which was not heated, remains blue.
Example 6 Six tubes contain aqueous solutions of glycerol, glucose, formalin, phenol, acetic and formic acid. Using the reagents and equipment on the table, determine the substances in the test tubes. Describe the course of the definition. Write the reaction equations on the basis of which the substances were determined.
Reagents: CuSO 4 5%, NaOH 5%, NaHCO 3 10%, bromine water.
Equipment: test tube rack, pipettes, water bath or hot plate.
Solution
1. Determination of acids.
When carboxylic acids interact with sodium bicarbonate solution, carbon dioxide is released:
HCOOH + NaHCO 3 → HCOONa + CO 2 + H 2 O;
CH 3 COOH + NaHCO 3 → CH 3 COONa + CO 2 + H 2 O.
Acids can be distinguished by reaction with bromine water. Formic acid decolorizes bromine water
HCOOH + Br 2 \u003d 2HBr + CO 2.
Bromine does not react with acetic acid in aqueous solution.
2. Determination of phenol.
In the interaction of glycerin, glucose, formalin and phenol with bromine water, only in one case is the solution cloudy and a white precipitate of 2,4,6-tribromophenol is observed.
Glycerin, glucose and formalin are oxidized by bromine water, and the solution becomes discolored. Glycerin under these conditions can be oxidized to glyceraldehyde or 1,2-dihydroxyacetone.
.
Further oxidation of glyceraldehyde leads to glyceric acid.
HCHO + 2Br 2 + H 2 O → CO 2 + 4HBr.
The reaction with a freshly prepared precipitate of copper (II) hydroxide makes it possible to distinguish between glycerol, glucose and formalin.
When glycerol is added to copper (II) hydroxide, the blue cheesy precipitate dissolves and a bright blue solution of complex copper glycerate is formed. When heated, the color of the solution does not change.
When glucose is added to copper (II) hydroxide, a bright blue solution of the complex is also formed
.
However, when heated, the complex is destroyed and the aldehyde group is oxidized, and a red precipitate of copper oxide (I) precipitates.
.
Formalin reacts with copper (II) hydroxide only when heated to form an orange precipitate of copper (I) oxide
HCHO + 4Cu(OH) 2 → 2Cu 2 O↓ + CO 2 + 5H 2 O.
All described interactions can be presented in Table 3 for the convenience of definition.
Table 3
Determination results
Literature
1. Traven V. F. Organic chemistry: A textbook for universities: In 2 volumes / V. F. Traven. - M .: ICC "Akademkniga", 2006.
2. Smolina T. A. et al. Practical work in organic chemistry: Small workshop. Textbook for universities. / T. A. Smolina, N. V. Vasilyeva, N. B. Kupletskaya. – M.: Enlightenment, 1986.
3. Kucherenko N. E. et al. Biochemistry: Workshop /N. E. Kucherenko, Yu. D. Babenyuk, A. N. Vasiliev and others - K .: Vyshcha school, Publishing house at Kyiv. un-those, 1988.
4. Shapiro D. K. Workshop on biological chemistry. - Mn: The highest school, 1976.
5. V. K. Nikolaenko. Solving problems of increased complexity in general and inorganic chemistry: A teacher's guide, Ed. G.V. Lisichkina - K .: Rad.shk., 1990.
6. S. S. Churanov. Chemistry Olympiads at school: A guide for teachers. - M .: Education, 1962.
7. Moscow City Chemistry Olympiads: Guidelines. Compiled by V.V. Sorokin, R.P. Surovtseva - M: 1988
8. Modern chemistry in the problems of international Olympiads. V. V. Sorokin, I. V. Svitanko, Yu. N. Sychev, S. S. Churanov - M.: Chemistry, 1993
9. E. A. Shishkin. Teaching students to solve qualitative problems in chemistry. - Kirov, 1990.
10. Chemical Olympiads in problems and solutions. Parts 1 and 2. Compiled by Kebets A.P., Sviridov A.V., Galafeev V.A., Kebets P.A. - Kostroma: Publishing House of KGSHA, 2000.
11. S. N. Perchatkin, A. A. Zaitsev, and M. V. Dorofeev. Chemistry Olympiads in Moscow. - M .: MIKPRO Publishing House, 2001.
12. Chemistry 10-11: Collection of problems with solutions and answers / V. V. Sorokin, I. V. Svitanko, Yu. N. Sychev, S. S. Churanov. ASTREL, 2001.
This task was proposed to 11th grade students at the practical round of the III (regional) stage of the All-Russian Chemistry Olympiad for schoolchildren in the 2009-2010 academic year.
The name "silver" comes from the Assyrian "sartsu" (white metal). The word "argentum" is probably related to the Greek "argos" - "white, shiny."
Finding in nature. Silver is much less common in nature than copper. In the lithosphere, silver accounts for only 10 -5% (by mass).
Native silver is very rare, most of the silver is obtained from its compounds. The most important silver ore is silver luster, or argentite Ag 2 S. As an impurity, silver is present in almost all copper and lead ores.
Receipt. Almost 80% of silver is obtained along with other metals during the processing of their ores. Separate silver from impurities by electrolysis.
Properties. Pure silver is a very soft, white, malleable metal characterized by exceptionally high electrical and thermal conductivity.
Silver is a low-active metal, which is referred to as the so-called noble metals. It does not oxidize in air either at room temperature or when heated. The observed blackening of silver products is the result of the formation of black Ag 2 S silver sulfide on the surface under the influence of hydrogen sulfide contained in the air:
Blackening of silver also occurs when objects made from it come into contact with food products containing sulfur compounds.
Silver is resistant to dilute sulfuric and hydrochloric acids, but soluble in nitric and concentrated sulfuric acids:
Application. Silver is used as a component of alloys for jewelry, coins, medals, solders, tableware and laboratory glassware, for silvering parts of apparatus in the food industry and mirrors, as well as for the manufacture of parts for vacuum devices, electrical contacts, electrodes, for water treatment and as a catalyst in organic synthesis.
Recall that silver ions, even in negligible concentrations, are characterized by a strongly pronounced bactericidal effect. In addition to water treatment, this finds application in medicine: colloidal solutions of silver (protargol, collargol, etc.) are used to disinfect mucous membranes.
Silver compounds. Silver oxide (I) Ag 2 O is a dark brown powder, exhibits basic properties, is poorly soluble in water, but gives the solution a slightly alkaline reaction.
This oxide is obtained by carrying out the reaction, the equation of which is
The silver (I) hydroxide formed in the reaction is a strong but unstable base; it decomposes into oxide and water. Silver oxide (I) can be obtained by acting on silver with ozone.
An ammonia solution of silver oxide (I) is known to you as a reagent: 1) for aldehydes - as a result of the reaction, a “silver mirror” is formed; 2) for alkynes with a triple bond at the first carbon atom - as a result of the reaction, insoluble compounds are formed.
An ammonia solution of silver oxide (I) is a complex compound of diammine silver (I) hydroxide OH.
Silver nitrate AgNO 3 , also called lapis, is used as an astringent bactericidal agent, in the production of photographic materials, in electroplating.
Silver fluoride AgF is a yellow powder, the only one of the halides of this metal that is soluble in water. Obtained by the action of hydrofluoric acid on silver oxide (I). It is used as an integral part of phosphors and a fluorinating agent in the synthesis of fluorocarbons.
Silver chloride AgCl is a white solid that forms as a white cheesy precipitate upon detection of chloride ions interacting with silver ions. Under the action of light, it decomposes into silver and chlorine. Used as photographic material, but much less than silver bromide.
Silver bromide AgBr is a light yellow crystalline substance formed by the reaction between silver nitrate and potassium bromide. Previously, it was widely used in the manufacture of photographic paper, film and photographic film.
Silver chromate Ag 2 CrO 4 and silver dichromate Ag 2 Cr 2 O 7 are dark red crystalline substances that are used as dyes in the manufacture of ceramics.
Silver acetate CH 3 COOAg is used in electroplating for silvering metals.
Carbon dioxide
1. aldehyde
Ammonia solution of silver oxide
Oxidative
2. restorative
3. amphoteric
4. acidic
Lipoic acid
2. hydroxylipoic acid
3. nitrolipoic acid
4. amino lipoic acid
A-2-hydroxybutanedioic acid, B-2-oxobutanedioic acid
2. A-2-oxobutanedioic acid, B-2-hydroxybutanedioic acid
3. A - dihydroxybutanedioic acid, B - 2-oxobutanedioic acid
4. A - 2-hydroxybutanedioic acid, B - butanedioic acid
21. The final product of the reduction of 5-nitrofurfural is ..
1. 5-hydroxyfurfural
Aminofurfural
3. 5-methoxyfurfural
4. 5-methylaminofurfural
22. Malic acid is oxidized with the participation of NAD + in
Oxaloacetic acid
2. acetic acid
3. succinic acid
4. oxalic acid
23. A substance of composition C 4 H 8 O, when interacting with a freshly prepared solution of Cu (OH) 2, isobutyric acid is formed, is called ...
Methylpropanal
2) Butanone
3) 2-methylpropanol-1
Butanal
24. Oxidative NAD + - dependent deamination of amino acids proceeds through the stage of formation ...
5. hydroxy acids
Imino acids
7. unsaturated acids
8. polyhydric acids
25. The formation of cystine from cysteine refers to ...
1. addition reactions
2. substitution reactions
3. oxidation reactions
Nucleophilic addition reactions
26. Oxidative NAD + dependent deamination of 2-aminopropanoic acid
formed...
1. 2 - hydroxypropanoic acid
2. 2 - oxopropanoic acid
3. 2 - methylpropanoic acid
4. 2 - methoxypropanoic acid
27. Aldehydes are reduced to ...
1. carboxylic acids
Primary alcohols
3. secondary alcohols
4. Epoxy
28. When ketones are reduced, ...
1. primary alcohols
2. polyhydric alcohols
secondary alcohols
4. carboxylic acids
29. Epoxides are formed during the oxidation of bonds with oxygen:
4. C = C
30. A qualitative reaction to unsaturated hydrocarbons is their oxidation with potassium permanganate. This creates:
1. carboxylic acids
2. aldehydes
Diols
4. aromatic compounds
31. Oxidation of ethyl alcohol in the body occurs with the participation of the coenzyme:
1. OVER +
3. hydroquinone
4. cyanocobalamin
31. When ethyl alcohol is oxidized in the body, the following is formed:
1. hemoglobin
Acetaldehyde
3. amino acids
4. carbohydrates
32. The composition of NAD + and NADH includes a nucleic base ____:
adenine
4. cytosine
33. The structure of riboflavin includes a heterocycle ______…
1.porphyrin
3. quinoline
Isoalloxazine
34. Oxidation of 4-methylpyridine produces….
A nicotinic acid
2. isonicotinic acid
3. stearic acid
4. butyric acid
35. An imino acid is an intermediate product in ....
1. when aromatic compounds are oxidized with oxygen
Oxidative deamination of amino acids
3. when reducing disulfides
4. in the oxidation of thioalcohols
36. Lactose belongs to reducing bioses and is oxidized to ...
1. lactonic acid
Lactona
3. lactobionic acid
4. lactide
37. When nitrofurfural is reduced, it forms ....
1. furatsilin
2. furallidone
Aminofurfural
4. amidopyrine
38. Oxidative deamination of α-alanine results in…
pyruvic acid
2. oxalic acid
3. lactic acid
4. oxaloacetic acid
39. When glucose is reduced, …
Sorbitol
2. glucuronic acid
4. gluconic acids
40. Tyrosine is formed during the hydroxylation reaction ...
Phenylalanine amino acids
2. tryptophan amino acids
3. pyridine heterocyclic compound
4. Adrenaline hormone
41. Nitro compounds are transformed in the body by reduction to
1. nitrite
Aminov
3. hydroxylamines
4. oximes
42. Amines can be obtained by the reaction ...
1.oxidation of nitro compounds
Recovery of nitro compounds
3. polymerization of nitro compounds
4. dehydration of nitro compounds
43. Disulfides are obtained as a result of an oxidation reaction ...
Sulphonic acids
2. thioalcohols
3. amino alcohols
4. sulfates
44. In the body, lactic acid under the action of NAD + ……. to pyruvic acid:
Oxidized
2. recoverable
4.hydrolyzed
45. In the body, pyruvic acid under the action of NADH ……. to lactic acid:
1. oxidized
Recovering
4.hydrolyzed
46. Isoallaxosin in the composition of riboflavin is restored in the body to:
1. dihydroxyisoallaxosine
Dihydroisoallaxosine
3. allaxosin
4. dihydroxyallaxosine
47. Coenzyme OVER+ is…
oxidized form
2. restored form
3. tautameric form
4.mesomeric form
48. NADH is a _________ form of coenzyme
1. oxidized
restored
3. tautameric
4. mesomeric
49. The composition of the coenzyme NAD + includes carbohydrate ....
1. fructofuranose
2. glucofuranose
3.glucopyranose
Ribofuranose
50. How many phosphoric acid residues are included in the coenzyme nicotinamide adenine dinucleotide.
51. Nicotinamide, which is part of NAD +, NADH, NADP +, NADPH is called a vitamin:
52. In vivo, 2-oxoglutaric acid is reduced to glutamic acid with the participation of the coenzyme ...
NADH
53. In the body, ethyl alcohol is oxidized to acetaldehyde with the participation of the coenzyme ...
1. OVER +
54. Calcium gluconate used in medicine is a salt of D - gluconic acid. D - gluconic acid is formed when glucose is oxidized with bromine water. What characteristic group is oxidized by bromine during the formation of this acid?
1. alcohol
Aldehyde
3. hydroxyl
4. sulfhydryl
55. Glucose oxidation reactions are used to detect it in biological fluids (urine, blood). The easiest way in the glucose molecule is oxidized ...
1. alcohol groups
Hydrocarbon skeleton
3. carbonyl group
4. hydrogen atoms
54. Nitroso compounds are an intermediate product of …..
1. amine recovery
2. amine oxidation
Nicotine
2. paraffin wax
3. naphthalene
4. guanine
56. To what fragment of the coenzyme NAD + and NADH does the “+” sign refer?
1. Phosphoric acid residues
1. nicotinamide
ribose
4. adenine
57. Hydroquinones contain…
1. two aldehyde groups
2. two carboxyl groups
Two hydroxyl groups
4. two amino groups
58. FAD is an active form of…..
1. coenzyme Q
2. vitamin K 2
3. vitamin b 2
4. adrenaline
59. FAD in the process of oxidation in the body….
1. accepts two protons and two electrons (+ 2H + , + 2e)
2. gives up two protons and two electrons (-2H +, - 2e)
3.or give or take depending on the substrate
4. does not donate or accept protons
60. Choose an aromatic heterocyclic system that is part of the FADH 2 coenzyme.
Isoallaxosin
2. nicotinamide
3. dihydroisoallaxosin
4. dihydroquinone
61. Select the nucleic base that is part of the FAD.
adenine
4. cytosine
62. Select the product that is formed during the oxidation of succinate (succinic acid salt) with the participation of NAD +.
1. malate (salt of malic acid)
2. pyruvate (salt of pyruvic acid)
Oxoacids
4. carboxylic acids
68. Choose a product that is formed during the oxidative deamination of glutamic acid.
1. 2-oxoglutaric acid
Oxoglutaric acid
3. citric acid
4. malic acid
69. Flavin adenine dinucleotide (FAD +) in redox reactions exhibits ...
1. restorative properties
2. amphoteric properties
oxidative properties.
4. acidic properties
70. Coenzyme Q is a derivative of ….
1. naphthoquinone
Benzoquinone
3. quinoline
4. naphthalene
71. Menaquinone (vitamin K 2) is a derivative of….
Naphthoquinone
2. benzoquinone
3. quinoline
4. naphthalene
72. What is the name of the intermediate product of the oxidation of double bonds:
1. hydroxide
Epoxide
73. Choose the correct name of the final product of the following transformation:
1. hydroxylamine
Amine
3. nitrosyl
4. nitrosamine
74. Choose the correct name of the final product of the reaction:
Lipoic acid
2. dehydrolipoic acid
3. citric acid
4. fatty acid
75. Choose the correct name of the proposed connection:
1. flavin adenine dinucleotide
2. isoallaxosin
Riboflavin
4. flavin adenine mononucleotide
76. Choose the correct continuation of the definition: an oxidizing agent in organic chemistry is a compound that ...
3. donates only electrons
Accepts only electrons
77. Choose the correct continuation of the definition: a reducing agent in organic chemistry is a compound that ...
1. donates two protons and two electrons
2. accepts two protons and two electrons
Donates only electrons
4. accepts only electrons
78. What type of reactions can be attributed to the conversion of ethyl alcohol into acetaldehyde with the participation of NAD + .
1. neutralization
2. dehydration
Oxidation
4. attachment - splitting off
79. What acid is formed during the oxidation of ethylbenzene:
1. toluidine
2. benzoic + formic
3. salicylic
4. benzoic + acetic
80. To what products are ubiquinones reduced in the body? Choose the correct answer.
Hydroquinones
2.menoquinones
3. phylloquinones
4. naphthoquinones
81. Indicate the reaction by which the most active hydroxyl radical is formed in the body
1. H 2 O 2 + Fe 2+
2. About 2 . + O 2 . + 4 H +
82. What radical is called superoxide anion radical
2. About 2 .
83. Indicate the reaction by which superoxide anion-radical is formed in the body
1. About 2 + e
84. Indicate the reaction by which dismutation is carried out
superoxide anion radicals
3. About 2 . + O 2 . + 4 H +
4.RO2. + RO 2 .
85. Indicate the reaction by which hydrogen peroxide is destroyed in the body without the formation of free radicals
1. H 2 O 2 → 2 OH.
3. About 2 . + O 2 . + 4 H +
4.RO2. + RO 2 .
Carbon dioxide
17. The oxidizing agent in the reaction of the silver mirror is ____ ...
1. aldehyde
2. ammonia solution of silver nitrate
ammonia solution of silver oxide
4. ammonia solution of silver chloride
18. In the silver mirror reaction, aldehydes exhibit _________ properties.
Oxidative
2. restorative
3. amphoteric
4. acidic
19. Dihydrolipoic acid is oxidized to ____….
Lipoic acid
2. hydroxylipoic acid
3. nitrolipoic acid
4. amino lipoic acid
20. Choose from the suggested answers reaction products A and B
My light, mirror, tell me, tell the whole truth ... how did the ammonia solution give you a wonderful ability to reflect light and show a face looking at you? In fact, there is no secret. known since the end of the 19th century thanks to the work of German chemists.
- the metal is quite resistant, it does not rust and does not dissolve in water. You can silver water, but no one will say that it is a solution of silver. Water will remain water, even if it is refined and disinfected. So they learned to purify water in ancient times and still use this method in filters.
But silver salts and oxides willingly enter into chemical reactions and dissolve in liquids, resulting in new substances that are in demand both in technology and in everyday life.
The formula is simple - Ag 2 O. Two silver atoms and an oxygen atom form silver oxide, which is sensitive to light. However, other compounds found more use in photography, but the oxide showed a disposition to ammonia reagents. In particular, to ammonia, which our grandmothers used to clean products when they darkened.
Ammonia is a compound of nitrogen and hydrogen (NH 3). Nitrogen makes up 78% of the earth's atmosphere. It is everywhere, as one of the most common elements on Earth. Aqueous ammonia solution is so widely used that it has received several names at once: ammonia water, caustic ammonium, ammonium hydroxide, caustic ammonia. It is easy to get confused in such a series of synonyms. If you dilute ammonia water to a weak, 10% solution, we get ammonia.
When chemists dissolved the oxide in ammonia water, a new substance appeared to the world - a complex compound of silver diamine hydroxide with very attractive properties.
The process is described by the chemical formula: Ag 2 O + 4NH 4 OH = 2OH + 3H2O.
Chemical reaction process and formula of ammonia water and silver oxide
In chemistry, this substance is also known as Tollens' reagent and is named after the German chemist Bernhard Tollens, who described the reaction in 1881.
If only the laboratory did not explode
It quickly became clear that the ammonia solution of silver oxide, although not stable, is capable of forming explosive compounds during storage, therefore, at the end of the experiments, it is recommended to destroy the residues. But there is also a positive side: in addition to the metal, nitrogen and oxygen are present in the composition, which, during decomposition, makes it possible to release silver nitrate, which is familiar to us as medical lapis. Now not so popular, but once they were cauterized and disinfected wounds. Where there is a danger of an explosion, there are means of treatment.
Nevertheless, the ammonia solution of silver oxide gained fame thanks to other, no less important phenomena: from explosives and mirror silvering to extensive research in anatomy and organic chemistry.
- When acetylene is passed through an ammonia solution of silver oxide, a very dangerous silver acetylenide is formed at the exit. It is able to explode when heated and mechanically, even from a smoldering splinter. When conducting experiments, care should be taken to isolate acetylenide in small quantities. How to clean laboratory glassware is detailed in the safety regulations.
- If silver nitrate is poured into a flask with a round bottom, an ammonia solution and glucose are added and heated in a water bath, then the metal part will settle on the walls and bottom, creating a reflection effect. The process was called the "silver mirror reaction". It is used in industry for the production of Christmas balls, thermoses and mirrors. Sweet glucose helps bring the product to a mirror shine. But fructose does not have this property, although it is sweeter.
- Tollens' reagent is used in pathological anatomy. There is a special technique (Fontana-Masson method) for staining tissues, with the help of which, at autopsy, melanin, argentaffin cells and lipofuscin (an aging pigment involved in intercellular exchange) are determined in tissues.
- It is used in organic chemistry for the analysis and detection of aldehydes, reducing sugars, hydroxycarboxylic acids, polyhydroxyphenols, primary ketoalcohols, aminophenols, α-diketones, alkyl- and arylhydroxylamines, alkyl- and arylhydrazines. Here is an important and necessary reagent. He contributed a lot to organic research.
As you can see, silver is not only jewelry, coins and photoreagents. Solutions of its oxides and salts are in demand in various fields of human activity.
Interaction with an ammonia solution of silver oxide (I) - "reaction of a silver mirror".
Silver oxide (I) is formed as a result of the interaction of silver nitrate (I) with NH 4 OH.
Metallic silver is deposited on the walls of the test tube in the form of a thin layer, forming a mirror surface.
Interaction with copper (II) hydroxide.
For the reaction, freshly prepared Cu (OH) 2 with alkali is used - the appearance of a brick-red precipitate indicates the reduction of divalent copper to monovalent due to the oxidation of the aldehyde group.
Polymerization reactions (characteristic of lower aldehydes).
Linear polymerization.
During evaporation or prolonged standing of a formaldehyde solution, a polymer is formed - paraformaldehyde: n (H 2 C \u003d O) + nH 2 O → n (paraformaldehyde, paraform)
Polymerization of anhydrous formaldehyde in the presence of a catalyst - iron pentacarbonyl Fe(CO) 5 - leads to the formation of a high-molecular compound with n=1000 - polyformaldehyde.
Cyclic polymerization (trimerization, tetrametrization).
Cyclic polymer
Polycondensation reactions.
Polycondensation reactions are the processes of formation of high-molecular substances, during which the combination of the initial monomers of molecules is accompanied by the release of such low-molecular products as H2O, HCl, NH3, etc.
In an acidic or alkaline environment, when heated, formaldehyde forms high-molecular products with phenol - phenol-formaldehyde resins of various structures. First, in the presence of a catalyst, an interaction occurs between the formaldehyde molecule and the phenol molecule with the formation of phenol alcohol. When heated, phenol alcohols condense to form phenol-formaldehyde polymers.
Phenol-formaldehyde resins are used to produce plastics.
Ways to get:
1. oxidation of primary alcohols:
a) catalytic (cat. Cu, t);
b) under the action of oxidizing agents (K 2 Cr 2 O 7, KMnO 4 in an acidic environment).
2. catalytic dehydrogenation of primary alcohols (cat. Cu, 300 o C);
3. hydrolysis of dihaloalkanes containing 2 halogen atoms at the first carbon atom;
4. formaldehyde can be obtained by catalytic oxidation of methane:
CH 4 + O 2 → H 2 C \u003d O + H 2 O (cat. Mn 2+ or Cu 2+, 500 o C)
5. acetaldehyde is obtained by the Kucherov reaction from acetylene and water in the presence of mercury (II) salts.
Practical lesson number 5.
Topic: "Carboxylic acids".
Lesson type: combined (studying new material, repetition and systematization of what has been covered).
Class type: practical lesson.
Time spending: 270 minutes.
Location: room for practical work in chemistry (No. 222).
Lesson objectives:
Educational:
1. to achieve an understanding of the relationship between the structure of substances and their chemical properties;
2. consolidate knowledge about the chemical properties of carboxylic acids;
3. learn how to write reaction equations that characterize the chemical properties of these homologous series;
4. consolidate knowledge about qualitative reactions to functional groups of organic substances and the ability to confirm these properties by writing reaction equations.
Educational- to educate students' ability to think logically, to see cause-and-effect relationships, the qualities necessary in the work of a pharmacist.
After class, the student should know:
1. classification, isomerism, nomenclature of carboxylic acids;
2. basic chemical properties and methods for obtaining carboxylic acids;
3. qualitative reactions for carboxylic acids.
After class, the student should be able to:
1. write equations of chemical reactions that characterize the properties of carboxylic acids.
Plan-structure of the lesson
