A significant difference in the structure and properties of organic compounds from inorganic ones, the uniformity of the properties of substances of the same class, the complex composition and structure of many organic materials determine the features of the qualitative analysis of organic compounds.

In the analytical chemistry of organic compounds, the main tasks are the assignment of analyzed substances to a certain class of organic compounds, the separation of mixtures and the identification of isolated substances.

Distinguish organic elemental analysis designed to detect elements in organic compounds, functional– to detect functional groups and molecular- to detect individual substances by special properties of molecules or a combination of elemental and functional analysis data and physical constants.

Qualitative elemental analysis

The elements most commonly found in organic compounds (C, N, O, H, P, S, Cl, I; less often As, Sb, F, various metals) are usually detected using redox reactions. For example, carbon is detected by oxidizing an organic compound with molybdenum trioxide when heated. In the presence of carbon, MoO 3 is reduced to the lower oxides of molybdenum and forms molybdenum blue (the mixture turns blue).

Qualitative functional analysis

Most reactions for the detection of functional groups are based on oxidation, reduction, complex formation, and condensation. So, for example, unsaturated groups are detected by the bromination reaction at the site of double bonds. The bromine solution becomes colorless:

H 2 C \u003d CH 2 + Br 2 → CH 2 Br - CH 2 Br

Phenols are detected by complexation with iron(III) salts. Depending on the type of phenol, complexes of various colors (from blue to red) are formed.

Qualitative molecular analysis

When performing a qualitative analysis of organic compounds, two types of problems are usually solved:

1. Discovery of a known organic compound.

2. Study of an unknown organic compound.

In the first case, knowing the structural formula of an organic compound, qualitative reactions to the functional groups contained in the compound molecule are selected to detect it. For example, phenyl salicylate is the phenyl ester of salicylic acid:

can be detected by functional groups: phenol hydroxyl, phenyl group, ester group and azo coupling with any diazo compound. The final conclusion about the identity of the analyzed compound to a known substance is made on the basis of qualitative reactions, necessarily involving data on a number of physicochemical constants - melting points, boiling points, absorption spectra, etc. The need to use these data is explained by the fact that different organic compounds can have the same functional groups .

In the study of an unknown organic compound, qualitative reactions are carried out for individual elements and the presence of various functional groups in it. Having received an idea about the set of elements and functional groups, the question of the structure of the compound is decided on the basis of quantitative definitions of elemental composition and functional groups, molecular weight, UV, IR, NMR mass spectra.

MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION

ROSTOV STATE CONSTRUCTION UNIVERSITY

Approved at the meeting

Department of Chemistry

METHODOLOGICAL INSTRUCTIONS

to laboratory work

"QUALITATIVE ANALYSIS OF ORGANIC COMPOUNDS"

Rostov-on-Don, 2004

UDC 543.257(07)

Guidelines for the laboratory work "Qualitative analysis of organic compounds". – Rostov n/a: Rost. state builds. un-t, 2004. - 8 p.

The instructions provide information about the features of the analysis of organic compounds, methods for detecting carbon, hydrogen, nitrogen, sulfur and halogens.

Methodical instructions are intended for work with students of the specialty 1207 full-time and part-time forms of education.

Compiled by: E.S. Yagubyan

Editor N.E. Gladkikh

Templan 2004, pos.175

Signed for publication on May 20, 2004. Format 60x84/16

Writing paper. Risograph. Uch.- ed. l. 0.5. Circulation 50 copies. Order 163.

__________________________________________________________________

Editorial and publishing center

Rostov State Construction University.

344022, Rostov-on-Don, st. Socialist, 162

 Rostov State

building university, 2004

Safety precautions when working in the laboratory of organic chemistry

1. Before starting work, it is necessary to familiarize yourself with the properties of the substances used and obtained, to understand all the operations of the experiment.

2. You can start work only with the permission of the teacher.

3. When heating liquids or solids, do not point the opening of the cookware at yourself or your neighbors; do not look into the cookware from above, as an accident may occur in case of possible ejection of the heated substance.

4. Handle concentrated and fuming acids in a fume hood.

5. Carefully add concentrated acids and alkalis into the test tube, be careful not to spill them on your hands, clothes, table. If acid or alkali gets on your skin or clothes, rinse them off quickly with plenty of water and contact your teacher for help.

6. If corrosive organic matter comes into contact with the skin, then rinsing with water is in most cases useless. Wash with a suitable solvent (alcohol, acetone). Apply the solvent as quickly as possible and in large quantities.

7. Do not pour the excess of the taken reagent and do not pour it back into the bottle from which it was taken.

Qualitative analysis allows you to establish which elements are part of the test substance. Organic compounds always contain carbon and hydrogen. Many organic compounds contain oxygen and nitrogen in their composition, halides, sulfur, and phosphorus are somewhat less common. The listed elements form a group of elements - organogens, most often found in the molecules of organic substances. However, organic compounds can contain almost any element of the periodic system. So, for example, in lecithins and phosphatides (components of the cell nucleus and nervous tissue) - phosphorus; in hemoglobin - iron; in chlorophyll - magnesium; in the blue blood of some mollusks - complex-bound copper.

Qualitative elemental analysis consists in the qualitative determination of the elements that make up an organic compound. To do this, the organic compound is first destroyed, then the elements to be determined are converted into simple inorganic compounds, which can be studied by known analytical methods.

The elements that make up organic compounds, during a qualitative analysis, as a rule, undergo the following transformations:

With CO 2 ; H H 2 O; N - NH 3; CI - CI -; S SO 4 2-; R RO 4 2-.

The first test of the study of an unknown substance to check whether it belongs to the class of organic substances is calcination. At the same time, very many organic substances turn black, charred, thus revealing the carbon that is part of them. Charring is sometimes observed under the action of water-removing substances (for example, concentrated sulfuric acid, etc.). Such charring is especially pronounced when heated. The smoky flame of candles, burners are examples of carbonization of organic compounds, proving the presence of carbon.

For all its simplicity, the charring test is only an auxiliary, indicative technique and has limited application: a number of substances cannot be charred in the usual way. Some substances, for example, alcohol and ether, even with weak heating evaporate before they have time to char; others, such as urea, naphthalene, phthalic anhydride, sublimate before charring.

A universal way to discover carbon in any organic compound, not only in solid, but also in liquid and gaseous states of aggregation, is the combustion of a substance with copper oxide (P). In this case, carbon is oxidized with the formation of carbon dioxide CO 2, which is detected by the turbidity of lime or barite water.

Practical work No. 1

Reagents : paraffin (C 14 H 30

Equipment :

Note:

2. The halogen in organic matter can be detected by the flame color reaction.

Work algorithm:

Pour lime water into the receiver tube.

Connect the test tube with the mixture to the test tube with a gas outlet tube with a stopper.

Heat the test tube with the mixture in the flame of an alcohol lamp.

Ignite the copper wire in the flame of an alcohol lamp until a black coating appears on it.

Bring the cooled wire into the test substance and again bring the spirit lamp into the flame.

Conclusion:

pay attention to: changes occurring with lime water, copper sulfate (2).

What color does the flame of the spirit lamp turn into when the test solution is added?

Practical work No. 1

"Qualitative analysis of organic compounds".

Reagents: paraffin (C 14 H 30 ), lime water, copper oxide (2), dichloroethane, copper sulfate (2).

Equipment : metal stand with foot, spirit lamp, 2 test tubes, cork with gas tube, copper wire.

Note:

carbon and hydrogen can be detected in organic matter by its oxidation with copper oxide (2).

halogen in organic matter can be detected using a flame color reaction.

Work algorithm:

1st stage of work: Melting of paraffin with copper oxide

1. Assemble the device according to fig. 44 on page 284, for this, place 1-2 g of copper oxide and paraffin in the bottom of the test tube, heat it up.

2nd stage of work: Qualitative determination of carbon.

1. Pour lime water into the receiver tube.

2. Connect the test tube with the mixture to the test tube with a gas outlet tube with a stopper.

3.Heat the test tube with the mixture in the flame of an alcohol lamp.

3rd stage of work: Qualitative determination of hydrogen.

1. In the upper part of the test tube with the mixture, place a piece of cotton wool, putting copper sulfate (2) on it.

4th stage of work: Qualitative determination of chlorine.

1. Ignite the copper wire in the flame of an alcohol lamp until a black coating appears on it.

2. Insert the cooled wire into the test substance and again bring the spirit lamp into the flame.

Conclusion:

1. pay attention to: changes occurring with lime water, copper sulfate (2).

2. What color is the flame of the spirit lamp colored when the test solution is added.

Most drugs used in medical practice are organic substances.

To confirm that a drug belongs to a particular chemical group, it is necessary to use identification reactions that should detect the presence of a certain functional group in its molecule (for example, an alcohol or phenolic hydroxyl, a primary aromatic or aliphatic group, etc.). Such an analysis is called a functional group analysis.

Analysis by functional groups is based on the knowledge acquired by students in the study of organic and analytical chemistry.

Information

Functional groups - these are groups of atoms that are highly reactive and easily interact with various reagents with a noticeable specific analytical effect (color change, odor, gas or precipitate, etc.).

Identification of preparations by structural fragments is also possible.

Structural fragment - this is the part of the drug molecule that interacts with the reagent with a noticeable analytical effect (for example, anions of organic acids, multiple bonds, etc.).

Functional groups

Functional groups can be divided into several types:

2.2.1. containing oxygen:

a) hydroxyl group (alcohol and phenolic hydroxyl):

b) aldehyde group:

c) keto group:

d) carboxyl group:

e) ester group:

f) simple ether group:

2.2.2. Containing nitrogen:

a) primary aromatic and aliphatic amino groups:

b) secondary amino group:

c) tertiary amino group:

d) amide group:

e) nitro group:

2.2.3. Sulfur containing:

a) thiol group:

b) sulfamide group:

2.2.4. Halogen containing:

2.3. Structural fragments:

a) double bond:

b) phenyl radical:

2.4. Anions of organic acids:

a) Acetate ion:

b) tartrate ion:

c) citrate ion:

d) benzoate ion:

This methodological manual provides the theoretical foundations for the qualitative analysis of structural elements and functional groups of the most common methods of analysis of medicinal substances in practice.

2.5. IDENTIFICATION OF ALCOHOLIC HYDROXYL

Medicines containing alcohol hydroxyl:

a) Ethyl alcohol

b) Methyltestosterone

c) Menthol

2.5.1. Esters formation reaction

Alcohols in the presence of concentrated sulfuric acid form esters with organic acids. Low molecular weight ethers have a characteristic odor, high molecular weight ones have a certain melting point:

Alcohol ethyl acetate

Ethyl (characteristic smell)

Methodology: 0.5 ml of acetic acid, 1 ml of concentrated sulfuric acid are added to 2 ml of ethyl alcohol 95% and heated to a boil - a characteristic smell of ethyl acetate is felt.

2.5.2. Oxidation reactions

Alcohols are oxidized to aldehydes by adding oxidizing agents (potassium dichromate, iodine).

Overall reaction equation:

Iodoform

(yellow sediment)

Methodology: 0.5 ml of ethyl alcohol 95% is mixed with 5 ml of sodium hydroxide solution, 2 ml of 0.1 M iodine solution are added - a yellow precipitate of iodoform gradually precipitates, which also has a characteristic odor.

2.5.3. Reactions for the formation of chelate compounds (polyhydric alcohols)

Polyhydric alcohols (glycerol, etc.) form blue chelate compounds with a solution of copper sulfate and in an alkaline medium:

glycerine blue intense blue

precipitate color solution

Methodology: 1-2 ml of sodium hydroxide solution is added to 5 ml of copper sulfate solution until a precipitate of copper (II) hydroxide is formed. Then add a solution of glycerin until the precipitate dissolves. The solution turns intense blue.

2.6 IDENTIFICATION OF PHENOLIC HYDROXYL

Medicinal products containing phenolic hydroxyl:

a) Phenol b) Resorcinol

c) Sinestrol

d) Salicylic acid e) Paracetamol

2.6.1. Reaction with iron (III) chloride

Phenols in a neutral medium in aqueous or alcoholic solutions form salts with iron (III) chloride, colored blue-violet (monatomic), blue (resorcinol), green (pyrocatechol) and red (phloroglucinol). This is due to the formation of cations C 6 H 5 OFe 2+, C 6 H 4 O 2 Fe +, etc.

Methodology: to 1 ml of an aqueous or alcoholic solution of the test substance (phenol 0.1:10, resorcinol 0.1:10, sodium salicylate 0.01:10) add from 1 to 5 drops of iron (III) chloride solution. Characteristic coloration is observed.

2.6.2. Oxidation reactions (indophenol test)

a) Reaction with chloramine

When phenols interact with chloramine and ammonia, indophenol is formed, which is colored in various colors: blue-green (phenol), brownish-yellow (resorcinol), etc.

Methodology: 0.05 g of the test substance (phenol, resorcinol) is dissolved in 0.5 ml of chloramine solution, 0.5 ml of ammonia solution is added. The mixture is heated in a boiling water bath. Staining is observed.

b) Lieberman's nitrosoreaction

The colored product (red, green, red-brown) is formed by phenols, in which ortho- and pair-provisions have no substitutes.

Methodology: a grain of a substance (phenol, resorcinol, thymol, salicylic acid) is placed in a porcelain cup and moistened with 2-3 drops of a 1% solution of sodium nitrite in concentrated sulfuric acid. Coloring is observed, which changes with the addition of sodium hydroxide.

in) Substitution reactions (with bromine water and nitric acid)

The reactions are based on the ability of phenols to be brominated and nitrated due to the replacement of a mobile hydrogen atom in ortho- and pair-provisions. The bromo derivatives precipitate as a white precipitate, while the nitro derivatives are yellow.

resorcinol white precipitate

yellow staining

Methodology: bromine water is added dropwise to 1 ml of a solution of a substance (phenol, resorcinol, thymol). A white precipitate forms. When adding 1-2 ml of dilute nitric acid, a yellow color gradually appears.

2.7. IDENTIFICATION OF THE ALDEHYDE GROUP

Medicinal substances containing an aldehyde group

a) formaldehyde b) glucose

2.7.1. Redox reactions

Aldehydes are easily oxidized to acids and their salts (if the reactions proceed in an alkaline medium). If complex salts of heavy metals (Ag, Cu, Hg) are used as oxidizing agents, then as a result of the reaction, a precipitate of metal (silver, mercury) or metal oxide (copper (I) oxide) precipitates.

a) reaction with ammonia solution of silver nitrate

Methodology: 10-12 drops of ammonia solution and 2-3 drops of a substance solution (formaldehyde, glucose) are added to 2 ml of silver nitrate solution, heated in a water bath at a temperature of 50-60 ° C. Metallic silver is released in the form of a mirror or a gray precipitate.

b) reaction with Fehling's reagent

red precipitate

Methodology: 2 ml of Fehling's reagent is added to 1 ml of an aldehyde (formaldehyde, glucose) solution containing 0.01-0.02 g of the substance, heated to boiling, a brick-red precipitate of copper oxide precipitates.

2.8. IDENTIFICATION OF THE ESTER GROUP

Medicinal substances containing an ester group:

a) Acetylsalicylic acid b) Novocaine

c) Anestezin d) Cortisone acetate

2.8.1. Reactions of acid or alkaline hydrolysis

Medicinal substances containing an ester group in their structure are subjected to acid or alkaline hydrolysis, followed by the identification of acids (or salts) and alcohols:

acetylsalicylic acid

acetic acid

salicylic acid

(white precipitate)

purple staining

Methodology: 5 ml of sodium hydroxide solution is added to 0.01 g of salicylic acid and heated to a boil. After cooling, sulfuric acid is added to the solution until a precipitate forms. Then 2-3 drops of a solution of ferric chloride are added, a purple color appears.

2.8.2. hydroxam test.

The reaction is based on alkaline ester hydrolysis. During hydrolysis in an alkaline medium in the presence of hydroxylamine hydrochloride, hydroxamic acids are formed, which, with iron (III) salts, give red or red-violet iron hydroxamates. Copper(II) hydroxamates are green precipitates.

hydroxylamine hydrochloride

hydroxamic acid

iron(III) hydroxamate

anestezin hydroxylamine hydroxamic acid

iron(III) hydroxamate

Methodology: 0.02 g of the substance (acetylsalicylic acid, novocaine, anestezin, etc.) is dissolved in 3 ml of ethyl alcohol 95%, 1 ml of an alkaline solution of hydroxylamine is added, shaken, heated in a boiling water bath for 5 minutes. Then add 2 ml of dilute hydrochloric acid, 0.5 ml of 10% solution of iron (III) chloride. A red or red-violet color appears.

2.9. LACTONE DETECTION

Medicinal substances containing a lactone group:

a) Pilocarpine hydrochloride

The lactone group is an internal ester. The lactone group can be determined using the hydroxam test.

2.10. IDENTIFICATION OF THE KETO GROUP

Medicinal substances containing a keto group:

a) Camphor b) Cortisone acetate

Ketones are less reactive than aldehydes due to the lack of a mobile hydrogen atom, so oxidation takes place under harsh conditions. Ketones readily condense with hydroxylamine hydrochloride and hydrazines. Oximes or hydrazones (precipitates or colored compounds) are formed.

camphor oxime (white precipitate)

phenylhydrazine sulfate phenylhydrazone

(yellow coloration)

Methodology: 0.1 g of a medicinal substance (camphor, bromcamphor, testosterone) is dissolved in 3 ml of ethyl alcohol 95%, 1 ml of a solution of phenylhydrazine sulfate or an alkaline solution of hydroxylamine is added. The appearance of a precipitate or a colored solution is observed.

2.11. IDENTIFICATION OF THE CARBOXY GROUP

Medicinal substances containing a carboxyl group:

a) Benzoic acid b) Salicylic acid

c) Nicotinic acid

The carboxyl group easily reacts due to the mobile hydrogen atom. There are basically two types of reactions:

a) formation of esters with alcohols(see section 5.1.5);

b) formation of complex salts by heavy metal ions

(Fe, Ag, Cu, Co, Hg, etc.). This creates:

Silver salts, white

Gray mercury salts

Salts of iron (III) pinkish-yellow color,

Salts of copper (II) blue or blue,

Lilac or pink cobalt salts.

The following is the reaction with copper(II) acetate:

nicotinic acid blue precipitate

Methodology: to 5 ml of a warm solution of nicotinic acid (1:100), 1 ml of a solution of acetate or copper sulfate is added, a blue precipitate forms.

2.12. IDENTIFICATION OF A SIMPLE ETHER GROUP

Medicinal substances containing a simple ether group:

a) Diphenhydramine b) Diethyl ether

Ethers have the ability to form oxonium salts with concentrated sulfuric acid, which are colored orange.

Methodology: 3-4 drops of concentrated sulfuric acid are applied to a watch glass or a porcelain cup and 0.05 g of a medicinal substance (diphenhydramine, etc.) is added. A yellow-orange color appears, gradually turning into brick red. When water is added, the color disappears.

For diethyl ether, the reaction with sulfuric acid will not be performed due to the formation of explosive substances.

2.13. IDENTIFICATION OF PRIMARY AROMATIC

AMINO GROUPS

Medicinal substances containing a primary aromatic amino group:

a) Anestezin

b) Novocaine

Aromatic amines are weak bases, since the lone electron pair of nitrogen is shifted towards the benzene nucleus. As a result, the ability of the nitrogen atom to attach a proton is reduced.

2.13.1. Azo dye formation reaction

The reaction is based on the ability of the primary aromatic amino group to form diazonium salts in an acidic medium. When a diazonium salt is added to an alkaline solution of β-naphthol, a red-orange, red or crimson color appears (azo dye). This reaction is given by local anesthetics, sulfamides, etc.

diazonium salt

azo dye

Methodology: 0.05 g of a substance (anesthesin, novocaine, streptocide, etc.) is dissolved in 1 ml of dilute hydrochloric acid, cooled in ice, 2 ml of 1% sodium nitrite solution are added. The resulting solution is added to 1 ml of an alkaline solution of β-naphthol containing 0.5 g of sodium acetate.

A red-orange, red or crimson color or an orange precipitate appears.

2.13.2. Oxidation reactions

Primary aromatic amines are easily oxidized even by atmospheric oxygen, forming colored oxidation products. Bleach, chloramine, hydrogen peroxide, iron (III) chloride, potassium dichromate, etc. are also used as oxidizing agents.

Methodology: 0.05-0.1 g of a substance (anesthesin, novocaine, streptocide, etc.) is dissolved in 1 ml of sodium hydroxide. To the resulting solution add 6-8 drops of chloramine and 6 drops of a 1% phenol solution. As it is heated in a boiling water bath, a color appears (blue, blue-green, yellow-green, yellow, yellow-orange).

2.13.3. Lignin test

This is a type of condensation reaction of a primary aromatic amino group with aldehydes in an acidic medium. It is made on wood or newsprint.

Aromatic aldehydes contained in lignin ( P-hydroxy-bezaldehyde, lilac aldehyde, vanillin - depending on the type of lignin) interact with primary aromatic amines. Forming Schiff bases.

Methodology: several crystals of the substance are placed on lignin (newsprint), 1-2 drops of hydrochloric acid, diluted. An orange-yellow color appears.

2.14. IDENTIFICATION OF THE PRIMARY ALIPHATIC

AMINO GROUPS

Medicinal substances containing a primary aliphatic amino group:

a) Glutamic acid b) γ-Aminobutyric acid

2.14.1. Ninhydrin test

Primary aliphatic amines are oxidized by ninhydrin when heated. Ninhydrin is a stable hydrate of 1,2,3-trioxyhydrindane:

Both equilibrium forms react:

Schiff's base 2-amino-1,3-dioxoindane

blue-violet coloration

Methodology: 0.02 g of the substance (glutamic acid, aminocaproic acid and other amino acids and primary aliphatic amines) is dissolved when heated in 1 ml of water, 5-6 drops of ninhydrin solution are added and heated, a purple color appears.

2.15. IDENTIFICATION OF THE SECONDARY AMINE GROUP

Medicinal substances containing a secondary amino group:

a) Dikain b) Piperazine

Medicinal substances containing a secondary amino group form precipitates of white, greenish-brown colors as a result of reaction with sodium nitrite in an acidic medium:

nitrosamine

Methodology: 0.02 g of the medicinal substance (dicaine, piperazine) is dissolved in 1 ml of water, 1 ml of sodium nitrite solution mixed with 3 drops of hydrochloric acid is added. A precipitate falls out.

2.16. IDENTIFICATION OF THE TERTIARY AMINO GROUP

Medicinal substances containing a tertiary amino group:

a) Novocaine

b) Diphenhydramine

Medicinal substances that have a tertiary amino group in their structure have basic properties, and also exhibit strong reducing properties. Therefore, they are easily oxidized to form colored products. For this, the following reagents are used:

a) concentrated nitric acid;

b) concentrated sulfuric acid;

c) Erdmann's reagent (a mixture of concentrated acids - sulfuric and nitric);

d) Mandelin's reagent (solution of (NH 4) 2 VO 3 in sulfuric acid);

e) Frede's reagent (solution of (NH 4) 2 MoO 3 in sulfuric acid);

f) Brand's reagent (a solution of formaldehyde in sulfuric acid).

Methodology: 0.005 g of a substance (papaverine hydrochloride, reserpine, etc.) is placed on a Petri dish in the form of a powder and 1-2 drops of the reagent are added. Observe the appearance of the corresponding color.

2.17. IDENTIFICATION OF THE AMIDE GROUP.

Medicinal substances containing an amide and a substituted amide group:

a) Nicotinamide b) Nicotinic diethylamide

2.17.1. Alkaline hydrolysis

Medicinal substances containing an amide (nicotinamide) and a substituted amide group (ftivizide, fthalazol, purine alkaloids, nicotinic acid diethylamide), when heated in an alkaline medium, are hydrolyzed to form ammonia or amines and acid salts:

Methodology: 0.1 g of the substance is shaken in water, 0.5 ml of 1 M sodium hydroxide solution is added and heated. There is a smell of released ammonia or amine.

2.18. IDENTIFICATION OF THE AROMATIC NITRO GROUP

Medicinal substances containing an aromatic nitro group:

a) Levomycetin b) Metronilazole

2.18.1. Recovery reactions

Preparations containing an aromatic nitro group (levomycetin, etc.) are identified using the reduction reaction of the nitro group to the amino group, then the azo dye formation reaction is carried out:

Methodology: to 0.01 g of levomycetin add 2 ml of dilute hydrochloric acid solution and 0.1 g of zinc dust, heat in a boiling water bath for 2-3 minutes, filter after cooling. Add 1 ml of 0.1 M sodium nitrate solution to the filtrate, mix well and pour the contents of the tube into 1 ml of freshly prepared β-naphthol solution. A red color appears.

2.19. IDENTIFICATION OF THE SULFHYDRIL GROUP

Medicinal substances containing a sulfhydryl group:

a) Cysteine ​​b) Mercazolil

Organic medicinal substances containing a sulfhydryl (-SH) group (cysteine, mercazolil, mercaptopuril, etc.) form precipitates with salts of heavy metals (Ag, Hg, Co, Cu) - mercaptides (gray, white, green, etc. colors) . This is due to the presence of a mobile hydrogen atom:

Methodology: 0.01 g of the medicinal substance is dissolved in 1 ml of water, 2 drops of silver nitrate solution are added, a white precipitate is formed, insoluble in water and nitric acid.

2.20. IDENTIFICATION OF THE SULFAMIDE GROUP

Medicinal substances containing a sulfa group:

a) Sulfacyl sodium b) Sulfadimethoxine

c) Phthalazole

2.20.1. Salt formation reaction with heavy metals

A large group of medicinal substances that have a sulfamide group in the molecule exhibits acidic properties. In a weakly alkaline environment, these substances form precipitates of various colors with salts of iron (III), copper (II) and cobalt:

norsulfazole

Methodology: 0.1 g of sodium sulfacyl is dissolved in 3 ml of water, 1 ml of copper sulfate solution is added, a bluish-green precipitate is formed, which does not change upon standing (unlike other sulfonamides).

Methodology: 0.1 g of sulfadimesine is shaken with 3 ml of 0.1 M sodium hydroxide solution for 1-2 minutes and filtered, 1 ml of copper sulfate solution is added to the filtrate. A yellowish-green precipitate is formed, which quickly turns brown (unlike other sulfonamides).

The identification reactions of other sulfonamides are carried out similarly. The color of the precipitate formed in norsulfazol is dirty violet, in etazol it is grassy green, turning into black.

2.20.2. Mineralization reaction

Substances having a sulfamide group are mineralized by boiling in concentrated nitric acid to sulfuric acid, which is detected by the precipitation of a white precipitate after adding a solution of barium chloride:

Methodology: 0.1 g of the substance (sulfanilamide) is carefully (under draft) boiled for 5-10 minutes in 5 ml of concentrated nitric acid. Then the solution is cooled, carefully poured into 5 ml of water, stirred and a solution of barium chloride is added. A white precipitate falls out.

2.21. IDENTIFICATION OF ANIONS OF ORGANIC ACIDS

Medicinal substances containing acetate ion:

a) Potassium acetate b) Retinol acetate

c) Tocopherol acetate

d) Cortisone acetate

Medicinal substances that are esters of alcohols and acetic acid (retinol acetate, tocopherol acetate, cortisone acetate, etc.) are hydrolyzed when heated in an alkaline or acidic medium to form alcohol and acetic acid or sodium acetate:

2.21.1. Acetic ethyl ester formation reaction

Acetates and acetic acid interact with 95% ethyl alcohol in the presence of concentrated sulfuric acid to form ethyl acetate:

Methodology: 2 ml of an acetate solution is heated with an equal amount of concentrated sulfuric acid and 0.5 ml of 95 5 ethyl alcohol, the smell of ethyl acetate is felt.

2.21.2.

Acetates in a neutral medium interact with a solution of iron (III) chloride to form a complex red salt.

Methodology: 0.2 ml of a solution of iron (III) chloride is added to 2 ml of a neutral solution of acetate, a red-brown color appears, which disappears when diluted mineral acids are added.

Medicinal substances containing benzoate ion:

a) Benzoic acid b) Sodium benzoate

2.21.3. The reaction of formation of a complex salt of iron (III)

Medicinal substances containing benzoate ion, benzoic acid form a complex salt with a solution of iron (III) chloride:

Methodology: 0.2 ml of a solution of iron (III) chloride is added to 2 ml of a neutral solution of benzoate, a pinkish-yellow precipitate is formed, soluble in ether.

"Chemistry. Grade 10". O.S. Gabrielyan (gdz)

Qualitative analysis of organic compounds | Detection of carbon, hydrogen and halogens

Experience 1. Detection of carbon and hydrogen in an organic compound.
Work conditions:
The device was assembled as shown in Fig. 44 textbooks. Pour a pinch of sugar and a little copper oxide (II) CuO into the test tube. They put a small cotton swab in a test tube, somewhere at the level of two-thirds of it, then poured a little anhydrous copper sulphate CuSO 4 . The test tube was closed with a cork with a gas outlet tube, so that its lower end was lowered into another test tube with calcium hydroxide Ca(OH) 2 previously poured into it. Heated the test tube in the flame of a burner. We observe the release of gas bubbles from the tube, the turbidity of the lime water and the blueness of the white CuSO 4 powder.
C 12 H 22 O 11 + 24CuO → 12CO 2 + 11H 2 O + 24Cu
Ca(OH) 2 + CO 2 → CaCO 3 ↓ + H 2 O
CuSO 4 + 5H 2 O → CuSO 4 . 5H2O
Conclusion: The initial substance contains carbon and hydrogen, since carbon dioxide and water were obtained as a result of oxidation, and they were not contained in the CuO oxidizer.

Experience 2. Detection of halogens
Work conditions:
They took a copper wire, bent at the end with a loop with tongs, calcined it in a flame until a black coating of copper oxide (II) CuO formed. Then the cooled wire was dipped into a solution of chloroform and again brought into the flame of the burner. We observe the coloring of the flame in a bluish-green color, since copper salts color the flame.
5CuO + 2CHCl 3 \u003d 3CuCl 2 + 2CO 2 + H 2 O + 2Cu