ACTIVITY 1

Analysis of β-lactam antibiotics.

Objective. Learn how to analyze medicinesβ-lactam antibiotics (penicillins and cephalosporins).

Self preparation. Write formulas and chemical names benzylpenicillin, its sodium and novocaine salts, benzathine benzylpenicillin, phenoxymethylpenicillin, semi-synthetic penicillins: oxacillin sodium salt, ampicillin, carbenicillin disodium salt, cephalexin, cephalothin sodium salt. study the physical and Chemical properties of these substances, methods of qualitative and quantitative analysis. To study the features of obtaining medicinal substances-antibiotics, the features of their use in medical practice, storage conditions.

Tasks:

Answer the questions of incoming control;

Perform identification reactions in accordance with the requirements of the relevant regulatory documentation;

In the process of self-training and in the classroom, the student must acquire the following knowledge and skills:

Know:

Formulas, international, Russian and chemical names, appearance, properties and solubility of the proposed substances;

Identification reactions of the substances listed above;

Storage conditions, use of medicinal substances in medical practice.

Task for the lesson:

Conduct an analysis of drugs from the group of β-lactamides in accordance with the ND

Independent work students

Task I. Complete qualitative reactions on medicinal substances of natural and semi-synthetic penicillins.

1. Hydroxamic reaction. This reaction is a group-wide reaction to β-lactamides. When performing it, you should carefully follow the conditions of the methodology (the amount of alkali and acid), since hydroxamates heavy metals are formed only in certain ranges of pH values.

Execution Method:

a) 0.01 g of the drug is placed in a porcelain cup, 1 drop of a solution consisting of 1 ml of 1 M hydroxylamine hydrochloride solution and 0.3 ml of 1 M sodium hydroxide solution is added. After 2-3 minutes, add 1 drop of acetic acid solution to the mixture, mix thoroughly, then add 1 drop of copper nitrate solution. A green precipitate is formed.

b) In a porcelain cup, dissolve 0.005 g of the drug in 3 ml of water, add 0.1 g of hydroxylamine hydrochloride. After 5 minutes to the resulting solution was added 1.1 ml of 1N. hydrochloric acid solution and 3 drops of iron (III) chloride solution. A dirty red-purple color appears.

2. Reaction with hydrochloric acid. When interacting soluble salts penicillin with 25% hydrochloric acid, a white precipitate of the acid form of penicillin is released, soluble in an excess of the reagent.

Execution Method:

To 0.02 g of the drug dissolved in a test tube in 1 ml of water, a 25% solution of hydrochloric acid is added dropwise. A white precipitate is formed, soluble in excess acid.

Sulfur detection reaction.

To 0.01 g of the drug in a test tube add 2-3 ml of concentrated nitric acid and boil for 2-3 minutes. After cooling, 0.5 ml of barium chloride solution is added. A white precipitate falls out.

Reaction with a solution of silver nitrate.

0.002 g of the drug is dissolved in 20 ml of distilled water in a 50 ml test tube, 1 ml of diluted nitric acid and mix. Then add 1 ml of silver nitrate solution. White comes out after 2 minutes cheesy sediment, readily soluble in 1 ml of ammonia solution.

Reaction with ammonia solution of silver nitrate.

0.01 g of the drug is dissolved in 20 ml of distilled water in a heat-resistant tube and a solution consisting of 10 ml of silver nitrate solution and 10 ml of ammonia is added. The solution is then heated almost to boiling. A light brown color appears, turning to dark brown, and after 5 minutes a dark precipitate (metallic silver) is released.

While the precipitate of silver acetylenide was drying, the author separated a small part (about half a pea). I waited for this portion of silver acetylenide to dry, carefully crushed it into powder (with a plastic spatula on paper), spread it in a thin layer over a sheet of paper and brought the flame of a lighter. There was a rather loud explosion (especially considering the small portion of the substance). This made me think: if you blow up the bulk of silver acetylenide (obtained from 1 g of silver nitrate) in the laboratory, the whole floor will come running. But it was raining outside, and besides, it was dangerous to carry the almost dried sediment outside. Decided to try.

When the precipitate was completely dry, he glowed a steel wire red-hot in the flame of a burner and touched it to the center of the precipitate. There was a crack. A few sparks appeared at the touch point. And that's it. He took a burner and turned the flame on the sediment. Individual pops were heard, sparks appeared, but the bulk of the sediment remained unaffected.

He carefully transferred the sediment from the filter to the paper, very carefully crushed it into powder with a plastic spatula, swept the acetylenide into a pile and touched the center with burning paper. An explosion followed, but relatively weak. In slow motion, the video showed a yellow flash and sparks, however, the bulk of the substance remained intact. The sediment was well dried, and that it did not explode because it was still wet was out of the question.

Then I ground the acetylenide more thoroughly and placed it in a thin layer on a sheet of paper. From the touch of the flame of the lighter, a loud explosion occurred. It turned out that small, almost imperceptible amounts of acetylenide, which were smeared on a filter or paper on which the Ag 2 C 2 precipitate was crushed, exploded more strongly than a compact precipitate obtained from 1 g of silver nitrate.

Once it was possible to observe a small explosion when rubbing silver acetylenide.

Before the final drying of the precipitate, it should be crushed into powder with a plastic spatula and the substance should be placed in a thin layer on paper. Once dry, carefully ignite the silver acetylenide. There will be a strong bang, when watching the video in slow motion, a yellow flash and numerous sparks are noticeable. After the explosion, a black spot will remain on the paper.

It is not recommended to set fire to large amounts of silver acetylenide: not only for safety reasons, but also because in this case the experiment may not work out.

Unused acetylenide is decomposed in nitric acid, the resulting silver nitrate solution is used for other experiments.

On this I considered the experiment over, but the experiment received an unexpected continuation. The next day, a large dessicator was placed on the same table. Almost immediately there was an explosion: from friction, grains of silver acetylenide exploded, which were scattered on the table. A third of the table cover became dark (it was difficult to wash it off). On the second day there was an explosion when I put a bottle of mercury on the table: it was rather unpleasant. I had to carefully wipe the table with dilute acid.

Probably, over time, the sensitivity of dry silver acetylenide to friction and shock increases.

Tollens test (silver mirror reaction)

Tollens Bernhard Christian Gottfried(1841–1918), professor (Germany). The main researches are devoted to organic chemistry and biochemistry.

The reagent was proposed by Tollens in 1881. He created a method for determining carbohydrates.

1841 was born in Hamburg

1864 graduated from the University of Göttingen

1864-1873 worked in the laboratory of Sh. A. Nyurts at the Higher medical school in Paris 1873 professor at Gettygen University and director X imico-agronomic institute of this university.

Tollens Sample Preparation Methods

Add a few drops of alkali solution to 1 ml of silver nitrate solution.

A precipitate of silver oxide precipitates.

To the resulting precipitate, add dropwise ammonia solution (ammonia) until the precipitate is completely dissolved due to the formation of a complex compound.

AgNO 3 + NH 4 OH \u003d AgOH + NH 4 NO 3

2AgOH \u003d Ag 2 O ↓ + H 2 O

Silver oxide has the ability to dissolve in ammonia

Ag 2 O + 4NH 4 OH \u003d 2OH + H 2 O

complex connection -silver diamine hydroxide[Ag(NH 3 ) 2 OH

Save the resulting ammonia solution of silver oxide in a dark bottle for experiments.

Silver ammonia (water-acetone solution)

0.5 g of silver nitrate is dissolved in 5 ml of distilled water.

To this solution is added 5 ml of concentrated ammonia,

and then the liquid volume is adjusted with acetone to 100 ml.

Oxidative effect of silver oxideis explained by the fact that this substance is an oxide of a noble metal; therefore, the oxide is also unstable in the presence of a reducing agent, i.e. a substance that is easily oxidized, it easily gives off oxygen, as a result of which the release (reduction) of metallic silver occurs.

The reaction equation can be given in the usual form:

HCHO + Ag 2 O -> HCOOH + 2 Ag

Formic aldehyde

Metanal

Formalin

Or the full equation:

HCHO + 2OH -> HCOOH + 2Ag + 4NH 3 + H 2 O

The "silver mirror" reaction is as follows in presence of excess ammonia turns into a salt - ammonium formate HCOONH 4:

2[Ag(NH 3 ) 2] OH + HCOH = 2 Ag ↓ + HCOONH 4 + 3NH 3 + H 2 O

Ammonium formate

Glucose refers to aldoses (contains an aldehyde group in an open form),

CH 2 OH(CHOH) 4 CHO + 2OH→2Ag↓+ CH 2 OH(CHOH) 4 COONH 4

3NH 3 + 3H 2 O

A 2% solution of silver nitrate is poured into the flask by a quarter of the volume, then ammonia solution is gradually added (25% ammonia should be diluted 8-10 times) until the precipitate formed at the beginning dissolves in its excess.

Or Tollens' reagentcarefully add 0.5-1 ml of formalin along the wall and place the flask in a glass of hot (preferably boiling) water.

Soon a beautiful silver mirror forms in the flask. The flask can be heated without a water bath, directly on a small flame, carrying the flame around the flask without shaking it.

Mirror flask - experience!

Mirrors appeared long before our era. At first, they were metal plates polished to a shine made of gold, silver, copper, and also bronze - an alloy of copper and tin. According to the chronicles, with the help of bronze mirrors, Archimedes in 212 BC.

"burned ladies' ships in the battle of Syracuse.

Mirror making modern type(on glass) started in 1858 by the German chemist Justus von Liebig.

Liebig did the following. Having degreased inner surface flask with a solution of soda - sodium carbonate Na 2 CO 3, he washed it with water, ethyl alcohol C 2 H 5 OH and diethyl ether (C 2 H 5) 2 O. After that, Liebig poured several milliliters of a 10% aqueous solution of formaldehyde into the flask HCHO (formalin). Having added to the mixture a solution of an ammonium complex of silver of the composition OH, he carefully heated the flask, and after a few minutes it became mirror-like (silver stood out in the form of a thin coating on the walls of the flask). Subsequently, instead of formalin, Liebig began to use 10% glucose solution C 6 H 12 O 6 to obtain a "silver mirror".

SILVER MIRROR!

O. Holgin

Is it possible? Mirrors are silvered in special factories, in mirror workshops. This craft is ancient, with traditions and professional secrets - it is not easy to make a good mirror. Let's try anyway!

Of course, a mirror surface can be prepared without difficulty - the reaction of the "silver mirror" is set at school in the classroom. But a good mirror will not work, it will shine a little - and that's it. No, this is a real mirror. And you will certainly succeed if you work carefully and do not neglect the little things.

Important Warning: Use only distilled water. Powder "crocus" - specially prepared iron oxide ( III ) - sift through a fine sieve and dilute the resulting dust with distilled water. If you do not have "crocus", you can take any ready-made polishing liquid, they are sold in hardware stores. Put the even glass that you are going to make mirrored on the table. Check with a level that the table surface is level, and if not, place folded pieces of paper under the legs to level the surface. Do not take a large glass, it is better to start small. In order not to accidentally crush it, put on the table, for example, an old blanket.

Pour the polishing liquid on the glass and wipe it thoroughly in a circular motion using felt, felt (you can take an old hat) or a piece of soft leather. Rub the glass with gauze moistened with a suspension of finely ground and sifted pumice in water, rinse again with distilled water, wipe with a damp sponge, and then with a gauze pad moistened with a 0.15% tin chloride solution ( IV ), rinse again and wipe with a wrung out swab. Glass preparation is complete. This is a very important procedure. The quality of the future mirror depends on how carefully you completed it.

The treated surface must be silvered immediately. If for some reason you did not have time to prepare a solution for silvering, then lower the glass into warm distilled water and do not remove it from it until everything is ready. By the way, such an operation is useful in all cases: it is good if the glass is 8-10 degrees warmer than the silvering solution.

This solution must be prepared only with rubber gloves. It is obtained by mixing two solutions, each of which is prepared separately. We will indicate the amount of substances per liter of solution, and you can estimate for yourself how much solution you need.

First solution : 4 g silver nitrate, 10 ml 25% ammonia solution, 4 g caustic soda. The procedure for preparing the solution is not quite common. Dissolve all silver nitrate in 300 ml of water, pour 9/10 of the solution into a clean glass and add dropwise ammonia solution, stirring the liquid all the time with a glass rod. The cloudy liquid will become more and more transparent, and finally the color will disappear. Add a little silver nitrate solution - the solution will again become cloudy. Add a solution of caustic soda, then the solution will take on a light brown tint. Again, add the ammonia solution drop by drop, and the solution will brighten again, now it seems slightly bluish. Pour in the remaining silver nitrate solution and ammonia, stir well and add distilled water to a liter.

If you have to store this solution, then pour it into a bottle or vial with a well-fitted stopper. Do not store the solution in an open container!

Second race creat: per liter of solution - 100 g of refined sugar and 10 ml of diluted (approximately 10%) sulfuric or nitric acid. Dissolve sugar in distilled water in advance, add acid, boil for a quarter of an hour and add water to the calculated volume.

Mix both solutions: for one milliliter of the second solution (with sugar), take about 100 ml of the first solution (with silver nitrate). Exact Ratio will have to be determined by experience. If there is an excess of sugar solution, then flakes will begin to fall out during silvering; if, on the contrary, this solution is in short supply, then silvering will go too slowly. Stir the resulting mixture quickly and thoroughly; it will first turn orange-red and then turn black. This is a signal: it's time to start silvering. Don't miss the moment!

Pour the mixture immediately onto the glass. It will spread over the entire surface, and the glass will become dark, but then it will quickly begin to brighten, a layer of metallic silver is formed on it, which is restored from nitrate. After 5-10 minutes, carefully drive the mixture off the glass with gauze (or even better - a piece of suede) dipped in distilled water, pour the mixture again and hold it for another quarter of an hour. Rinse the already silvered surface with distilled water. If there are dark spots on the glass, they should be wiped with a swab with a mixture of pumice, then with a solution of tin chloride ( IV ), pour the mixture over these places again and rinse with water.

To check if enough silver has deposited on the glass, look through a mirror at a 60W lamp - it should be barely visible through the silvered glass.

The silver layer is not yet firmly attached to the glass. To strengthen it, put the mirror in a vertical position for an hour or two to heat up at a temperature of 100-150 o C. Use a drying cabinet, in extreme cases - a slightly heated oven. Once the mirror has cooled down, coat the silver film with a waterproof clear varnish from a spray bottle (the brush can damage it). After drying, apply a thick layer of opaque paint or black bituminous varnish over the varnish. Move with a brush or spray from a spray gun in only one direction: either from top to bottom or from left to right.

The mirror is almost ready. It remains only to put in order its front, non-silvered side. There may be streaks of silver on it; remove them with a swab dipped in weak solution of hydrochloric acid. If you get your hands dirty, then remove the stains with a slightly warmed hyposulfite solution and wash your hands thoroughly with warm water.

How much silver went into making the mirror? And how much silver is in a real mirror? The questions seem to be simple, but they are not so easy to answer. The film of silver is so thin that even if you have a micrometer, you can't measure it...

In order not to spoil a good mirror, take some fragment, remove a layer of varnish and paint with cotton wool soaked in acetone, and place a small crystal of iodine on a silver-plated surface. Already at room temperature, iodine evaporates rather quickly, its vapors spread over the glass, because they are much heavier than air. To prevent them from being dispersed by an accidental draft, cover the crystal with an inverted glass.

When iodine interacts with silver, silver iodide is formed, and a transparent spot slowly spreads near the crystal: iodide in a thin layer is transparent. And at the edges of the transparent spot, the silver film does not disappear, but becomes thinner. And as a result, colored rings appear on the mirror, which are seen especially well in reflected light.

Rings appear colored for the same reason they appear rainbow to us. bubble and oil stains on the water. This phenomenon is called the interference of light in thin films, it is studied in the course of physics. For us, the most important thing is this: the more rings, the thicker the silver film. If there are two of them, then the film thickness is about 0.03 microns, three rings correspond to 0.06 microns, four - 0.09, five - 0.12, six - 0.15, seven - 0.21 microns.

Knowing the thickness of the silver layer, it is easy to calculate the amount of silver: you just need to multiply the thickness by the area of ​​the mirror and multiply the resulting volume by the silver density (10.5 g/cm3). Here is a guideline for checking the calculation: a mirror with an area of ​​about square meter contains a little more than a gram of silver.

Experiments without explosions.

Reaction with ammonia solution of silver nitrate

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

Reaction with Fehling's reagent

Methodology: To 1 ml of an aldehyde solution (formaldehyde solution, chloral hydrate, hexamethylenetetramine, glucose) containing 0.01 - 0.02 g of the substance, add 2 ml of Fehling's reagent, heat to a boil. A brick-red precipitate of copper(I) oxide separates.

Methodology: To 2-3 drops of aldehyde solution (formaldehyde solution, 3% hexamethylenetetramine solution, 10% glucose solution) add 2-3 drops of Nessler's reagent and heat. A greyish-black precipitate of metallic mercury is released.

Condensation reactions

Aldehydes in concentrated sulfuric acid are condensed with phenols, colored quinones are formed. A red color appears (arylmethane dye).

In addition to phenols, aldehydes condense primary aromatic amines(forming Schiff bases) and hydrazines (as precipitate or colored product). Reaction type - nucleophilic substitution:

Methodology: To 1 ml of aldehyde solution add 1 ml alkaline solution hydroxylamine hydrochloride. Gradually precipitated oxime.

IDENTIFICATION OF THE KETO GROUP

Medicinal substances containing a keto group:

Ketones are less reactive than aldehydes due to the absence of a mobile hydrogen atom. Therefore, oxidation occurs under harsh conditions. Ketones readily condense with hydroxylamine hydrochloride and hydrazines. Oximes or hydrazones are formed.

Methodology: 0.1 g medicinal substance(camphor, bromocamphor, testosterone) is dissolved in 3 ml of ethyl alcohol 95%, 1 ml of a solution of 2,4-dinitrophenylhydrazine or an alkaline solution of hydroxylamine is added. The appearance of a precipitate or a colored solution is observed.

Let's continue the topic chemical experiments because we hope you enjoy them. This time we present to your attention another fascinating experience, during which we will receive a silver mirror.

Let's start by watching the video

We will need:
- capacity;
- silver nitrate;
- hot water;
- ammonia solution 10%;
- glucose;
- alcohol burner

Let's start with silver nitrate. We take about a gram from it and dilute in a small amount hot water.

Next, sodium hydroxide is added to the resulting solution. During this reaction, silver oxide is formed, which precipitates.

Next, add a 10% ammonia solution to the precipitate of silver oxide. It is necessary to pour in the ammonia solution until the precipitate dissolves.

During this reaction, silver ammonia is formed. Add 5 grams of glucose to the resulting solution.

Now you need to heat the resulting mixture. To do this, we light the alcohol burner and put a glass on it so that the mixture gradually heats up. During this reaction, very a large number of ammonia, so this reaction must be carried out either under a fume hood or outdoors. The reaction can also form silver nitrite, which is very dangerous substance Therefore, the dishes after the reaction must be thoroughly rinsed.

After some time, a thin layer of silver gradually begins to settle on the walls of the glass. The reaction is completed after about 15 minutes after the start of heating.

In order to get a more even layer of silver, you need to put a glass with the mixture in a large container, pour hot water into the container and put it on an alcohol burner. The temperature will thus be distributed evenly and the result will be more spectacular.