Installation for purification by distillation of organochlorine products and methods of purification by distillation of carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene. Preparation of anhydrous pure organic solvents Petrole

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INTRODUCTION

Solvent purity

Basic Precautions

Listed below are some rules to follow when cleaning and working with solvents;

A) Under no circumstances should sodium or other active metals or metal hydrides be used to dry liquids or acidic compounds (or halogenated compounds) that may act as oxidizing agents.

B) Vigorous drying agents (such as Na, CaH 2, LiAlH 4, H 2 SO 4, P 2 O 5) should not be used until preliminary rough drying has been carried out using conventional agents (Na 2 SO 4 and etc.) or the substance is not guaranteed to have a low water content.

C) Before distilling and drying ethers and other solvents, be sure to check for the presence of peroxides and remove them. To avoid the formation of peroxides, most ethers should not be stored in light or air for long periods of time.

D) It should be remembered that many solvents (for example, benzene, etc.) are toxic and have the ability to accumulate in the body; Therefore, inhalation of vapors from these solvents should be avoided. It should also be remembered that many solvents, with the exception of, for example, CCl 4 and CHCl 3, are highly flammable; Diethyl ether and CS 2 are especially dangerous in this regard.

E) It is recommended to store thoroughly purified solvents in sealed glass containers in an inert atmosphere (usually N 2 free of O 2). If tightness cannot be ensured, excess pressure of an inert gas should be created above the surface of the liquid. Long-term storage of some solvents is ensured by sealing a closed container with paraffin.

METHODS FOR RAPID DETERMINATION OF PEROXIDES IN LIQUIDS

1. The most sensitive method (allows you to determine up to 0.001% peroxide); Under the influence drops liquid containing peroxide, colorless ferrothiocyanate turns into red ferrithiocyanate. The reagent is prepared as follows: 9 g of FeSO 4 7H 2 O are dissolved in 50 ml of 18% HCl. Add some granular Zn and 5 g sodium thiocyanate; after the red color disappears, another 12 g of sodium thiocyanate is added and the solution is decanted from unreacted Zn into a clean flask.

2. A few milliliters of liquid are placed in a flask with a glass stopper. Add 1 ml of freshly prepared 10% aqueous KI solution, shake and leave to stand for 1 minute. The appearance of a yellow color indicates the presence of peroxide. A faster method is to add about 1 ml of liquid to an equal volume of glacial acetic acid containing about 100 mg of NaI or KI. A yellow color of the solution indicates the presence of a low concentration, while a brown color indicates a high concentration of peroxide.

3. The method for determining peroxides in water-insoluble liquids is as follows: a few milliliters of liquid are added to a solution containing about 1 mg of sodium bichromate, 1 ml of water and 1 drop of diluted H 2 SO 4. The blue color of the organic layer (perchromate ion) indicates the presence of peroxide.

4. A certain amount of liquid is “shaken off with a drop of pure mercury; in the presence of peroxide, a black film of mercury oxide is formed.

REMOVAL OF PEROXIDES (IN PARTICULAR FROM ETHERS)

1. Large quantities of peroxides are removed by keeping the liquids over alumina or by passing them through short columns filled with alumina. The use of activated alumina allows the solvent to be dried simultaneously. Precautionary measures: when passing solvents through the column, it is necessary to ensure that the aluminum oxide is completely wetted by the solvent; adsorbed peroxides should be eluted or washed away, for example, with 5% aqueous solution FeSO 4 (see below).

2. Peroxides are removed from water-insoluble liquids by shaking with a concentrated solution of ferrous iron salt (100 g of iron (II) sulfate, 42 ml of concentrated HCl, 85 ml of water). With this treatment, small amounts of aldehydes can be formed in some ethers, which are removed by washing with a 1% solution of KMnO 4, then with a 5% solution. aqueous NaOH solution and water.

3. One of the most effective reagents for removing peroxides is an aqueous solution of sodium pyrosulfite (also called metabisulfite Na 2 S 2 O 5), which quickly reacts with peroxides in stoichiometric ratios.

4. Peroxides in high concentrations are completely removed from ethers by washing in the cold with triethylenetetramine (25% by weight of ether).

5. Stannous chloride SnCl 2 is the only inorganic reagent that is effective in the solid state.

6. Peroxides are usually removed from water-soluble ethers by boiling the ether at reflux in the presence of 0.5 wt.% Cu 2 Cl 2 and subsequent distillation.

CLEANING METHODS

The use of the following purification methods makes it possible to obtain solvents with a degree of purity that in most cases satisfies the requirements of chemical and physical experiments (synthesis, kinetic studies, spectroscopy, determination of dipole moments, etc.). In this case, it is assumed that the experimenter uses industrially produced solvents with a certain standard degree of purity for cleaning (see Chapter 1), and not technical solvents containing a large number of impurities. Unless otherwise stated, distill the solvent. carried out at atmospheric pressure. If the method for crystallizing the solvent from another liquids, crystallization means freezing of the solvent being purified; in this case, up to 20% of the liquid is drained from the crystalline mass. In addition to the methods outlined here, so-called “adsorption filtration” using activated alumina can be recommended in many cases for the purification of solvents.

Aromatic hydrocarbons

Benzene of very high purity (bp 80.1°; mp 5.53°) is obtained by fractional crystallization from ethanol or methanol followed by distillation. When using the traditional purification method, benzene is shaken or mixed with concentrated sulfuric acid (100 ml per 1 liter of benzene) and then the acid layer is removed; the operation is repeated until the acid layer has a very faint color. Benzene is decanted and distilled. Purification using sulfuric acid removes thiophene, olefins and water from benzene.

Toluene(bp 110.6°) and xylenes cleaned in the same way; It should be remembered, however, that these hydrocarbons have a higher ability to sulfonate than benzene, therefore, when treating them with sulfuric acid, it is necessary to cool the mixture, maintaining the temperature below 30 ° C. In addition to sulfuric acid, it is also recommended to use CaCl 2 for drying, although, generally speaking, simple distillation may be sufficient, since these hydrocarbons form azeotropic mixtures with water or have much more high temperature boiling than water.

Acetone (bp 56.2°)

Acetone is very difficult to dry; the use of many of the commonly used drying agents (even MgSO 4) leads to condensation of acetone. For drying, it is convenient to use a 4A and K 2 CO 3 molecular sieve. Distillation over a small amount of KMnO 4 allows you to destroy the impurities contained in acetone, such as aldehydes. Very pure acetone is obtained as follows: saturated with dry NaI at 25-30°C, the solution is decanted and cooled to -10°C; NaI crystals form a complex with acetone, which is filtered and heated to 30°C; the resulting liquid is distilled.

Acetonitrile (bp 81.6°)

Acetonitrile containing water is pre-dried, then mixed with CaH 2 until gas evolution stops and distilled over P 2 O 5 (≤5 g/l) in a glass apparatus with a reflux condenser with a high reflux ratio. The distillate is refluxed over CaH 2 (5 g/l) for at least 1 hour, then slowly distilled, discarding the first 5% and the last 10% of the distillate in order to reduce the acrylonitrile content. If acetonitrile contains benzene as an impurity (absorption band in the UV spectrum at 260 nm, intense “tail” at 220 nm), the latter is removed by azeotropic distillation with water before treatment with P 2 O 5.

rubs-Butyl alcohol (bp 82°)

To obtain alcohol of very high purity (mp 25.4°), it is distilled over CaO, followed by repeated crystallization.

Dimethyl sulfoxide [i.e. kip. 189° (dec.)]

Dimethyl sulfoxide may contain, in addition to water, impurities of dimethyl sulfide and sulfone. To clean, it is held for 12 hours or more over fresh activated alumina, dryerite, BaO or NaOH. Then it is distilled under reduced pressure (~2-3 mmHg, bp 50°) over NaOH or BaO granules and stored over a 4A molecular sieve.

Dimethylformamide (bp 152°)

N,N-Dimethylformamide may contain impurities of water and formic acid. The solvent is mixed or shaken with KOH and distilled over CaO or BaO.

1,4-Dioxane (bp 102°)

Dioxane can contain large amounts of impurities, making it difficult to purify. It is known that many of the described methods are ineffective in purifying this solvent, as they lead to decomposition of the liquid. The traditional cleaning method is as follows. A mixture of 300 ml of water, 40 ml of concentrated HCI and 3 liters of dioxane is refluxed for 12 hours in a slow stream of nitrogen (to remove acetaldehyde, which is formed by hydrolysis of the glycol acetal impurity). The solution is cooled and KOH granules are added until they no longer dissolve and the layers separate. The dioxane layer (top layer) is decanted and dried over fresh potassium hydroxide. The dried dioxane is boiled over Na for 12 hours or until the Na retains a shiny surface. The solvent is then distilled over Na and stored in the dark under N 2 atmosphere.

LiAlH 4 should not be used to dry dioxane, since it can decompose at the boiling point of the solvent. In order to ensure the absence of oxygen and peroxides in purified dioxane, it is recommended to use benzophenoneketyl.

Diethyl ether (bp 34.5°)

In all cases, except where a ready-made "absolute" ether is used, the solvent should be checked for the presence of peroxides and treated accordingly. When working with ether, you must observe additional measures precautions due to the highly flammable nature of the solvent. Sufficiently dry ether can be obtained by drying and distillation over a sodium wire, but the most effective method is distillation over LiAlH 4 (or CaH 2).

Methanol (bp 64.5°)

In addition to water, methanol contains impurities of carbonyl and hydroxyl-containing compounds with the number of C atoms from 1 to 4, however, a solvent with a “reagent grade” purity usually contains only traces of such impurities. Acetone is removed from methanol as iodoform after treatment with NaOI. Most of the water can be removed by distillation, since methanol does not form azeotropic mixtures with water. Very dry methanol is obtained by keeping the solvent over 3A or 4A molecular sieves or passing through a column packed with these molecular sieves; the solvent is then dried over calcium hydride. It is not recommended to use dryerite as a drying agent for methanol! Residual water can also be removed using magnesium methoxide as follows: a mixture of 50 ml of methanol, 5 g of Mg in the form of chips and 0.5 g of sublimated iodine is refluxed until the solution becomes discolored and the evolution of hydrogen ceases. Then add 1 liter of methanol, reflux for about 30 minutes and carefully distill.

Nitroalkanes

Commercially available compounds with 1 to 3 carbon atoms can be purified fairly well by drying over calcium chloride or P 2 O 5 followed by careful distillation. High purity nitromethane is also obtained by fractional crystallization (mp -28.6°).

Nitrobenzene (bp 211°)

Nitrobenzene, purified by fractional crystallization (mp 5.76°) and distillation over P 2 O 5, is colorless. A solvent containing impurities quickly becomes colored over P 2 O 5 ; pure solvent remains colorless even after prolonged contact with P 2 O 5.

Pyridine (bp 115.3°)

Pyridine is dried for a long time over KOH granules, then distilled over BaO. It should be borne in mind that pyridine is very hygroscopic (forms a hydrate, bp 94.5°), so it is necessary to ensure that moisture does not enter the purified solvent.

2-Propanol [iso-propanol] (bp 82.4°)

2-Propanol forms an azeotropic mixture with water (9% water, bp 80.3°); water can be removed by refluxing or distillation over lime. The solvent is prone to the formation of peroxides, which are usually destroyed by refluxing over SnCl 2 . A fairly dry and pure solvent is obtained by distillation over anhydrous calcium sulfate; very dry alcohol is prepared using Mg according to the procedure described for methanol.

Sulfuric acid (boiling point about 305°)

According to Jolly, 100% acid is usually prepared by adding fuming sulfuric acid to standard 96% acid until the water content is converted to sulfuric acid. The completion time of this procedure is determined as follows: blow through the acid using a small rubber syringe wet air; the formation of fog indicates an excess of SO 3; if the acid is not yet 100%, no fog will form. This method allows you to adjust the acid composition with an accuracy of 0.02% (!). Sulfuric acid is very hygroscopic, so care must be taken to ensure that no moisture gets into it.

Carbon disulfide (bp 46.2°)

Carbon disulfide is a highly flammable and toxic liquid and special precautions must be taken when handling it. The solvent should be distilled very carefully, using a water bath, which is recommended to be heated to a temperature slightly above the boiling point of CS 2. Sulfur impurities are removed from carbon disulfide by shaking the solvent first with Hg, then with a cold saturated solution of HgCl 2 and then with a cold saturated solution of KMnO 4, after which it is dried over P 2 O 5 and distilled.

Tetrahydrofuran (bp 66°)

The solvent must be checked for the presence of peroxides and treated accordingly; traces of peroxides are removed by boiling a 0.5% suspension of Cu 2 Cl 2 in tetrahydrofuran for 30 minutes, after which the solvent is distilled. Tetrahydrofuran is then dried over KOH granules, refluxed and distilled over lithium aluminum hydride or calcium hydride. This method produces a very dry solvent.

Acetic acid (bp 118°)

Commercially available glacial acetic acid (~99.5%) contains impurities of carbonyl compounds, which are removed by refluxing in the presence of 2 to 5 wt.% KMnO 4 or excess CrO 3 , after which the acid is distilled. Traces of water are removed by heating by treating with a double or triple excess of triacetyl borate, which is prepared by heating a mixture of boric acid and acetic anhydride (1:5 by weight) at 60°C; the mixture of acetic acid and triacetyl borate is cooled and the resulting crystals are filtered off. After distillation, anhydrous acid is obtained. Acetic acid is also dehydrated by distillation over P 2 O 5 .

Carbon tetrachloride (bp 76.5°)

CS 2 impurities are removed from CCl 4 by stirring the hot solvent with a 10 vol.% concentrated alcohol solution of KOH. This procedure is repeated several times, after which the solvent is washed with water, dried over CaCl 2 and distilled over P 2 O 5 .

Chloroform (bp 61.2°)

Commercially available chloroform most often contains about 1% ethanol as a stabilizer that protects the chloroform from oxidation by atmospheric oxygen into phosgene. To clean the solvent, one of the following methods is recommended:

A) Chloroform is shaken with concentrated H 2 SO 4, washed with water, dried over CaCl 2 or K 2 CO 3 and distilled.

B) Chloroform is passed through a column filled with activated alumina (activity level 1) (about 25 g per 500 ml CHCI 3).

C) Chloroform is shaken several times with water (about half the volume of the solvent), dried over CaCl 2 and distilled over P 2 O 5.

The solvent purified by any of these methods is stored in the dark under N 2 atmosphere.

Ethanol (bp 78.3°)

Entering in. Sale of "absolute" ethanol contains about 0.1-0.5% water and, as a rule, 0.5-10% denaturing agent (acetone, benzene, diethyl ether or methanol, etc.). A more accessible and less expensive solvent is usually an azeotropic mixture with water (4.5%) (95% ethanol or rectified alcohol) (bp 78.2°). It is this solvent that is most often used in UV spectrophotometry (reagent grade or USP ethanol does not contain benzene or other denaturing agents). Pure ethanol is very hygroscopic and easily absorbs moisture; this circumstance should be taken into account when obtaining a dry solvent.

The following method is recommended to remove traces of water from absolute ethanol. A mixture of 60 ml of absolute ethanol, 5 g of Mg (chips) and a few drops of CCl 4 or CHCl 3 (catalyst) is refluxed until all the Mg is converted to ethylate. Add another 900 ml of absolute ethanol, reflux for 1 hour and distill. If it is necessary to ensure the absence of halogen compounds in the absolute solvent, highly volatile ethyl bromide can be used as a catalyst instead of CCl 4 or CHCl 3. The formation of a bulky precipitate when a benzene solution of aluminum ethoxide is added to ethanol makes it possible to detect the presence of up to 0.05% water in the solvent. Storing absolute ethanol over a molecular sieve 3A allows you to store a solvent with a water content of no more than 0.005%.

Most of the water from 95% alcohol is removed by refluxing over fresh lime (CaO) and subsequent distillation. Azeotropic distillation is recommended as another method: water is distilled off from a ternary azeotropic mixture, for example benzene-ethanol-water (bp 64.48°); then benzene is distilled off from a double azeotropic mixture of benzene-ethanol (bp 68.24°).

Ethyl acetate (bp 77.1°)

Commercially available ethyl acetate most often contains water, ethanol and acids as impurities; they are removed by washing the solvent with a 5% aqueous solution of sodium carbonate, then with a saturated solution of calcium chloride, after which they are dried over anhydrous potassium carbonate and distilled over P 2 O 5 .

Other solvents

Cellosolves and carbitols are purified by drying over calcium sulfate and distillation. Acid anhydrides are purified by fractional distillation from molten salts of the corresponding acids; Anhydrides with high molecular weight (6 carbon atoms, etc.) decompose during distillation at atmospheric pressure.

Distill substances at a temperature significantly lower than their boiling point. The essence of steam distillation is that high-boiling, immiscible or slightly miscible, i.e. Substances that are slightly soluble in water volatilize when water vapor is passed into them; then they condense together with the steam in the refrigerator. In order to determine whether a substance is volatile with water vapor, a small amount of it must be heated in a test tube with 2 ml of water. The bottom of a second test tube containing ice is held above this test tube. If the drops condensing on the cold bottom of the second test tube are cloudy, then the substance is volatile with water vapor. Table 6 Data on some substances distilled with steam Substance Boiling point, 0C Content of pure substance of a mixture of substance with substance in steam distillate, % Aniline 184.4 98.5 23 Bromobenzene 156.2 95.5 61 Naphthalene 218.2 99 .3 14 Phenol 182.0 98.6 21 Nitrobenzene 210.9 99.3 15 o-Cresol 190.1 98.8 19 The sequence of work is as follows. It is recommended to first heat the flask with liquid and water until almost boiling. This preheating is intended to prevent the volume of the mixture in the flask from increasing too much due to the condensation of water vapor during distillation. In the future, the distillation flask need not be heated. When a strong stream of steam comes out of the steam generator, close the rubber tube placed on the tee with a clamp and begin distillation with steam. A fairly strong stream of steam should pass through the liquid in the flask. A sign of the end of distillation is the appearance of a transparent distillate (pure water). If the substance being distilled has appreciable solubility in water (for example, aniline), a small amount of clear distillate should be collected. At the end of the distillation, open the clamp and only then extinguish the burners (thereby eliminating the danger of drawing liquid from the distillation flask into the steam generator). In the receiver, after distillation, two layers are obtained: water and organic matter. The latter is separated from the water in a separating funnel, dried in the usual way and distilled for final purification. Sometimes salting out and extraction are used to reduce the loss of a substance due to its partial solubility in water. High-boiling substances that are difficult to distill with steam having a temperature of 100°C can be distilled with superheated steam, unless there is a danger of decomposition of the substance at a higher temperature. To generate superheated steam, steam superheaters of various devices are used. Typically, steam from the steam generator enters a metal coil that has a pipe for measuring temperature and is heated by the flame of a strong burner. It is necessary to maintain a certain temperature of the superheated steam in order to control the rate of distillation and avoid decomposition of the substance. The distillation flask should be immersed in an oil or metal bath heated to the required temperature, and the neck of the flask should be tightly wrapped with asbestos cord. If distillation is carried out at temperatures above 120-130°C, it is necessary to connect first an air and then a water refrigerator to the distillation flask in series. The use of superheated steam makes it possible to increase the rate of distillation of poorly volatile substances many times over (Fig. 39). In contrast to ordinary, simple distillation, during which steam and condensate pass through the apparatus once in a direction, in countercurrent distillation, or rectification, part of the condensate constantly flows towards the steam. This principle is implemented in distillation distillation columns. Rectification is a method of separating or purifying liquids with fairly close boiling points by distillation using special columns in which rising vapors interact with liquid flowing towards them (reflux), which is formed as a result of partial condensation of vapors. As a result of repeated repetition of the processes of evaporation and condensation, the vapors are enriched in the low-boiling component, and the reflux, enriched in the high-boiling component, flows into the distillation flask. Efficient columns used in industry or scientific research can separate liquids that differ in boiling point by less than 1°C. Conventional laboratory columns allow the separation of liquids with a boiling point difference of at least 10°C. The distillation column must be thermally insulated so that the processes occurring in it occur under conditions as close as possible to adiabatic. If there is significant external cooling or overheating of the column walls, its correct operation is impossible. To ensure close contact of vapors with liquid, distillation columns are filled with a packing. Glass beads, glass or porcelain rings, short pieces of glass tubes or stainless steel wire, and glass spirals are used as nozzles. Distillation columns are also used with a star-type Christmas tree pin. The efficiency of the column depends on the amount of reflux supplied to the irrigation. To obtain a sufficient amount of reflux, the distillation column must be connected to a condenser. The role of a condenser with partial condensation of vapors can be performed by a conventional reflux condenser. A simple setup for separating a mixture of liquids is shown in Fig. 38. 52 Condensers are widely used, in which complete condensation of all vapors passing through the column occurs. Such condensers are equipped with a tap for distillate selection. Rectification can be carried out both at atmospheric pressure and in vacuum. As a rule, rectification in vacuum is carried out for high-boiling or thermally unstable mixtures. Questions for control: 1. Explain the types and methods of distillation. 2. In what cases is distillation used at atmospheric pressure, at reduced pressure (in vacuum) and with water steam. Why? 3. Explain the operating principle and design of a distillation device at atmospheric pressure. 4. Explain the operating principle and design of a steam distillation device. Practical part 4.1.4.1. Distillation at atmospheric pressure Reagents: substance to be purified. Equipment: device for simple distillation. Assemble the device for simple distillation at atmospheric pressure as shown in Fig. 38. Fig. 38. Device for simple distillation: 1 - Wurtz flask; 2 - thermometer; 3 - downward Liebig refrigerator; 4 - allonge; 5 - receiving flask. Using a funnel, distillation flask 1 is filled no more than two-thirds with the liquid being distilled. Before filling the device, measure the volume or weight of the liquid. The distillation apparatus is assembled from dry, clean parts and mounted on stands. Turn on the cooling water. A bath (water, oil) or a heating mantle is used as a heater. By controlling the temperature of the bath using a second thermometer 2 mounted on a tripod, the heating is set to such a level that ensures uniform, slow boiling of the contents of the flask. No more than two drops of clean and transparent distillate per second should fall into the receiver. Only under such conditions does the thermometer in the flask indicate the temperature corresponding to the equilibrium point between vapor and liquid; If distilled too quickly, the vapors easily overheat. The distillation temperature is recorded in a log. The distillation cannot be continued dry! It is completed at the moment when the boiling temperature is 2-3 degrees higher than the one at which the main fraction passed. At the end of the distillation, determine the volume or weight of the distillate, as well as the residue in the distillation flask. Exercise. Purify one of the proposed solvents as directed by the teacher. In organic synthesis, the “purity” of the solvents used is very important. Often even small impurities interfere with the reaction, so purification of solvents is an urgent task for a synthetic chemist. Chloroform 0 20 Bp.=61.2 C; nd =1.4455; d415=1.4985 An azeotropic mixture (chloroform-water-ethanol) contains 3.5% water and 4% alcohol, it boils at 55.5°C. Commercial chloroform contains alcohol as a stabilizer that binds phosgene formed during decomposition. Cleaning. Shake with concentrated sulfuric acid, wash with water, dry over calcium chloride and distill. Attention! Due to the risk of explosion, chloroform should not be brought into contact with sodium. Carbon tetrachloride 0 20 Bp = 76.8 C; nd =1.4603 An azeotropic mixture with water boils at 66°C and contains 95.9% carbon tetrachloride. A ternary azeotrope with water (4.3%) and ethanol (9.7%) boils at 61.8°C. Cleaning and drying. Distillation is usually sufficient. The water is removed in the form of an azeotropic mixture (the first parts of the distillate are discarded). If high demands are placed on drying and purification, then carbon tetrachloride is refluxed for 18 hours with phosphorus (V) oxide and distilled with a reflux condenser. Carbon tetrachloride must not be dried with sodium (risk of explosion!). Ethanol 0 Bp = 78.33 C; nd20=1.3616;d415=0.789 Ethanol is miscible with water, ether, chloroform, benzene in any ratio. The azeotropic mixture with water boils at 78.17°C and contains 96% ethanol. A ternary azeotrope mixture with water (7.4%) and benzene (74.1%) boils at 64.85°C. 54 Impurities. Synthetic alcohol is contaminated with acetaldehyde and acetone, ethyl alcohol obtained during fermentation is contaminated with higher alcohols (fusel oils). Pyridine, methanol and gasoline are added for denaturation. Drying. Dissolve 7 g of sodium in 1 liter of commercial “absolute” alcohol, add 27.5 g of phthalic acid diethyl ether and boil for 1 hour under reflux. Then it is distilled with a small column. Distilling alcohol contains less than 0.05 water. Traces of water can be removed from commercial “absolute” alcohol in another way: 5 g of magnesium is boiled for 2-3 hours with 50 ml of “absolute” alcohol, to which 1 ml of carbon tetrachloride is added, then 950 ml of “absolute” alcohol are added, and another 5 are boiled. h with reflux condenser. In conclusion, they distill. Water detection. Alcohol containing more than 0.05% water precipitates a voluminous white precipitate from the benzene solution of aluminum triethylate. 4.1.4.2. Steam distillation Reagents: substance to be purified. Equipment: device for simple distillation. Assemble the steam distillation apparatus as shown in Fig. 39. Fig. 39. Device for distillation with water steam: 1- steam generator; 2 - tee with clamp; 3 - distillation flask; 4 - refrigerator; 5 - allonge; 6 - receiving flask; 7 - safety tube; 8 – supply tube; 9 – tube that removes steam Steam is formed in steam generator 1 (a flask is also suitable instead). The safety tube 7 is used to equalize the pressure, the connecting link is used to release condensate. Steam through the supply tube 8 enters the distillation flask 3, which contains the mixture to be separated. Typically this flask is also heated. The distillate enters refrigerator 4, condenses and flows through allonge 5 into receiver 6. Small amounts of the substance can be distilled without using a steamer, but by adding a certain amount of water directly into the distillation flask. Task 1. Carry out steam distillation of natural raw materials (rose petals, spruce needles) to obtain an aqueous extract essential oil . To do this, natural raw materials are loaded into the flask, filled with water and distilled with steam. Task 2. Obtain anhydrous oxalic acid from its mixture with water by azeotropic distillation of water. Distillation of a mixture of two liquids that are insoluble in each other is also used to dry organic substances by the so-called azeotropic distillation of water. For this purpose, the substance to be dried is mixed with an organic solvent, for example, benzene or carbon tetrachloride, and the mixture is heated in a distillation apparatus. In this case, water is distilled off with vapor of the organic substance (at a temperature lower than the boiling point of the lowest boiling component of the mixture, for example, benzene or CCl4). With a sufficiently large amount of organic solvent, complete dehydration of the substance being dried can be achieved. 4.1.4.3. Rectification Reagents: substance to be purified. Equipment: Device for fractional distillation. Rectification at atmospheric pressure Assemble the device for distillation of the mixture as shown in Fig. 40. Fig. 40. Device for fractional distillation: 1 - distillation flask; 2 - reflux condenser; 3 - thermometer; 4 - refrigerator; 5 - allonge; 6 - receiving flask Task. Separate a mixture of ethanol and butanol into its components by rectification at atmospheric pressure. Collect the following fractions: a) up to 82°C (“pure ethanol”); b) from 83 to 110°C (intermediate fraction); c) remainder. Measure the volume of the fraction and residue. 4.1.4.4. Distillation in vacuum Reagents: substance to be purified. Equipment: Device for distillation under reduced pressure. 56 Fig. 41. Device for distillation under reduced pressure: 1 - Claisen flask or round-bottomed flask with a Claisen nozzle; 2 - capillary connected to a rubber hose with a clamp; 3 - thermometer; 4 - refrigerator; 5 - allonge; 6 - receiving flask; 7 - safety bottle; 8 - pressure gauge Task. Distill quinoline under reduced pressure. T kip. quinoline at atmospheric pressure -237.7°C, and at 17 mm Hg. Art. -114°C. Questions for the colloquium: 1. Why is a reflux condenser used in fractional distillation? 2. What are azeotropic mixtures? What methods are there for separating them? 3. At what temperature (above or below 100°C) will water boil in the mountains? Explain your answer. 4. Where do impurities remain when organic compounds are purified by distillation? 4.1.5. Thin layer chromatography (TLC) Chromatography refers to a whole group of physical and chemical separation methods based on the work of Tsvet (1903). ) and Kuhn (1931). There are chromatography in columns, thin layer, on paper, and gas. The separation of substances in these cases occurs either as a result of distribution between two liquid phases (partition chromatography), or due to different adsorbability of the substance by some adsorbent (adsorption chromatography). Thin layer chromatography involves using, for example, aluminum oxide as a sorbent. In this case, both distribution and adsorption play a role in separation. The mobile phase, in the flow of which the mixture to be separated moves, is called the eluent, and the solution leaving the stationary phase layer and containing the dissolved components of the mixture is called the eluate. Depending on the direction in which the eluent moves across the plate, there are:  ascending thin layer chromatography 57  descending thin layer chromatography  horizontal thin layer chromatography  radial thin layer chromatography. Ascending thin layer chromatography This type of chromatography is the most common and is based on the fact that the front of the chromatographic system rises along the plate under the action of capillary forces, i.e. the front of the chromatographic system moves from bottom to top. For this method, the simplest equipment is used, since any container with a flat bottom and a tight-fitting lid that can freely fit a chromatographic plate can be used as a chromatographic chamber. The ascending thin layer chromatography method has a number of disadvantages. For example, the rate at which the front rises along the plate occurs unevenly, i.e. in the lower part it is highest, and as the front rises it decreases. This is due to the fact that in the upper part of the chamber the saturation of solvent vapors is less, so the solvent from the chromatographic plate evaporates more intensely, therefore, its concentration decreases and the speed of movement slows down. To eliminate this drawback, strips of filter paper are attached to the walls of the chromatographic chamber, along which the rising chromatographic system saturates the chamber with vapor throughout its entire volume. Some chromatography chambers are divided into two trays at the bottom. This improvement allows not only to reduce the consumption of the chromatograph system (a smaller volume is required to obtain the required height of the chromatograph system) but also to use an additional cuvette for a solvent that increases the saturated vapor pressure in the chamber. Another disadvantage is the need to monitor the solvent front, since the solvent front line may “run away” to the upper edge. In this case, determine real value Rf is no longer possible. Descending thin layer chromatography This chromatography method is based on the fact that the front of the chromatographic system descends along the plate mainly under the influence of gravity, i.e. the front of the mobile phase moves from top to bottom. For this method, a cuvette with a chromatographic system is attached to the upper part of the chromatographic chamber, from which a solvent is supplied to the chromatographic plate using a wick, which flows down and the test sample is chromatographed. The disadvantages of this method include the complexity of the equipment. This method is mainly used in paper chromatography. 58 Horizontal thin layer chromatography This method is the most complex in terms of equipment but the most convenient. Thus, in the chromatographic chamber the plate is placed horizontally and the system is fed to one edge of the plate using a wick. The solvent front moves in the opposite direction. There is one more trick that allows you to simplify the camera extremely. To do this, a chromatographic plate on an aluminum base is slightly bent and placed in the chamber. In this case, the system will receive input from both sides simultaneously. Only plates with an aluminum backing are suitable for this purpose, since the plastic and glass base is “unbending”, i.e. does not retain its shape. The advantages of this method include the fact that in a horizontal cuvette, the system is saturated with vapors much faster, the speed of the front is constant. And when chromatography is performed on both sides, the front does not “run away”. Radial thin-layer chromatography Radial thin-layer chromatography involves applying the test substance to the center of the plate and adding an eluent that moves from the center to the edge of the plate. The distribution of the components of the mixture occurs between the water absorbed by the carrier1 and the solvent moving through this stationary phase (mobile phase). In this case, Nernst's law applies. The component of the mixture that is more easily soluble in water moves more slowly than the one that is more soluble in the mobile phase. Adsorption consists in the fact that adsorption equilibria are established between the carrier and the components of the mixture - each component has its own, resulting in different speeds of movement of the components. A quantitative measure of the rate of transfer of a substance when using a particular adsorbent and solvent is the Rf value (retardation factor or mobility coefficient). The value of Rf is determined as the quotient of the distance from the spot to the starting line divided by the distance of the solvent (front line) from the starting line: Distance from the spot to the starting line Rf = Distance from the solvent front to the start The value of Rf is always less than one, it does not depend on the length chromatograms, but depends on the nature of the chosen solvent and adsorbent, temperature, concentration of the substance, and the presence of impurities. Thus, at low temperatures, substances move more slowly than at higher temperatures. Contaminants contained in the mixture of solvents used, inhomogeneity of the adsorbent, and foreign ions in the analyzed solution can change the Rf value. 1 An adsorbent carrier, such as alumina, starch, cellulose, and water form a stationary phase. 59 Sometimes the factor Rs is used: Distance traveled by a substance from the line to the start Rs= Distance traveled by a substance, taken as a standard, from the line to the start In contrast to Rf, the value of Rs can be greater or less than 1. The value of Rf is determined by three main factors. FIRST FACTOR - the degree of affinity of the organic compound being chromatographed to the sorbent, which increases in the following series: alkanes< алкены < простые эфиры < нитросоединения < альдегиды < нитрилы < амиды < спирты < тиофенолы < карбоновые кислоты По мере увеличения числа функциональных групп энергия адсорбции возрастает (Rf уменьшается). Наличие внутримолекулярных взаимодействий, например водородных связей, наоборот уменьшает ее способность к адсорбции (Rf увеличивается). Так, о-нитрофенолы и о-нитроанилины имеют большее значение Rf , чем м- и п-изомеры. Плоские молекулы адсорбируются лучше, чем неплоские. ВТОРОЙ ФАКТОР - свойства самого сорбента, которые определяются не только химической природой вещества, но и микроструктурой его активной поверхности. В качестве сорбентов чаще всего используются оксид алюминия, силикагель, гипс с размером гранул 5-50 мкм. Оксид алюминия обладает удельной поверхностью 100- 200 м2/г, имеет несколько адсорбционных центров. Одни из них избирательно сорбируют кислоты, другие - основания. При этом для кислот c рКа <5 и оснований c рКа >9 is characterized by chemisorption. Aluminum oxide is also effective for separating acyclic hydrocarbons with different numbers of double and triple bonds. Silica gel (SiO2×H2O) has a significantly greater sorption capacity than aluminum oxide. In TLC, large-porous grades of silica gel with a pore size of 10-20 nm and a specific surface of 50-500 m2/g are used. Silica gel is chemically inert to most active organic compounds, however, due to its acidic properties (pH 3-5), it quite strongly sorbs bases with pKa>9. Gypsum is a sorbent with a small sorption capacity and low activity. Used for chromatography of polar compounds, as well as compounds containing a large number of different functional groups. THIRD FACTOR - the nature of the eluent, which displaces the molecules of the substances under study adsorbed on the active centers. In order of increasing eluent ability, eluents can be arranged in the following row: 60

Physical and chemical properties:
Carbon tetrachloride (methane tetrachloride, CHCl 4) is a colorless liquid. Sol. water in CCl 4 is about 1% (24°). Does not ignite. On contact with flame or heated objects, it decomposes to form phosgene. May contain CS 2, HCl, H 2 S, and organic sulfides as impurities.

Application area:
Used as a solvent; for extraction of fats and alkaloids; in the production of freons; in fire extinguishers; for cleaning and degreasing clothes in everyday life and in industrial conditions.

Receipt:
It is obtained by chlorination of CS 2 in the presence of catalysts; catalytic chlorination of CH 4 (together with CH 2 C1 2 and CHCl 3); by heating a mixture of coal and CaCl 2 at the temperature of a voltaic arc.

General nature of the toxic effect:

A drug with less vapor potency than chloroform. Regardless of route of entry, it causes severe liver damage: centrilobular necrosis and fatty degeneration. At the same time, it affects other organs: the kidneys (proximal renal tubules), alveolar membranes and pulmonary vessels. Lesions in the kidneys and lungs are less significant, developing, as a rule, after liver damage and as a result of a violation of general metabolism, but in some cases they play a significant role in the picture and outcome of poisoning. Most early sign toxic effects are considered to be changes in the level of a number of blood enzymes. A greater ability of the liver to regenerate after poisoning was revealed. Drinking alcohol while inhaling C.U. vapors, cooling, and increased oxygen content in the air increase the toxic effect. When extinguishing a flame with fire extinguishers and in general during strong heating, poisoning can occur from inhalation of thermal decomposition products of Ch.U.

According to existing views on the pathogenesis of the toxic effect of Ch.U., it is associated with free radical metabolites (type CC13) formed as a result of the hemolytic rupture of CCl 4 molecules. As a result of increased peroxidation of lipid complexes of intracellular membranes, the activity of enzymes and a number of cell functions (protein synthesis, ß-lipoprotein metabolism, drug metabolism) are disrupted, destruction of nucleotides occurs, etc. It is assumed that the main place of formation of free radical metabolites is the endoplasmic reticulum and microsomes cells.

Poisoning picture:

If very high concentrations are inhaled (by carelessly entering tanks and reservoirs, when extinguishing fires with fire extinguishers with C.U. in small enclosed spaces, etc.), either sudden death, or loss of consciousness or anesthesia. With milder poisoning and a predominant effect on the nervous system, headache, dizziness, nausea, vomiting, confusion or loss of consciousness are characteristic. Recovery occurs relatively quickly. Excitement sometimes has the character of strong attacks of a violent state. Poisoning in the form of encephalomyelitis, cerebellar degeneration, peripheral neuritis, optic neuritis, hemorrhage and fat embolism of the brain has been described. There is a known case of epileptiform convulsions and loss of consciousness on the 4th day after poisoning without significant damage to the liver and kidneys. At autopsy (in case of quick death) there are only hemorrhages and cerebral edema, pulmonary emphysema.

If poisoning develops slowly, symptoms of damage to the central nervous system within 12-36 hours, severe hiccups, vomiting, often prolonged, diarrhea, sometimes intestinal bleeding, jaundice, and multiple hemorrhages occur. Later - enlargement and tenderness of the liver, severe jaundice. Even later, symptoms of severe kidney damage appear. In other cases, symptoms of kidney damage precede signs of liver disease. Observations have shown that liver damage is pronounced in the first period and the stronger the faster death occurs; with later death, regenerative processes already exist in the liver tissue. Changes in the kidneys with early death are insignificant. If the kidneys are damaged, the amount of urine decreases; in the urine - protein, blood, cylinders. The content of non-protein nitrogen in the blood is increased, but the content of chlorides, calcium, and proteins is decreased. In severe cases, oliguria or complete anuria occurs (both the filtration and secretory functions of the kidneys are impaired). High blood pressure, edema, seizures, uremia - Pulmonary edema may develop and is often the immediate cause of death (edema is sometimes attributed to the administration of excess fluid during treatment). In more favorable cases after anuria - abundant diuresis, gradual disappearance of pathological elements in the urine, full recovery kidney function. Sometimes, apparently at not very high concentrations of Ch.U., the only sign of poisoning may be a decrease or cessation of urine output.

The consequence of acute poisoning with C.U. vapors can be a duodenal ulcer, pancreatic necrosis, anemia, leukocytosis, lymphopenia, changes in the myocardium, acute psychosis (Vasilieva). The outcome of poisoning can be yellow atrophy of the liver, as well as cirrhosis.

When taking C.U. orally, the picture of poisoning is the same as when inhaling vapors, although there are indications that the liver is predominantly affected in these cases.

The most characteristic pathological changes: parenchymal and fatty degeneration of the liver, as well as numerous necrosis in it; acute toxic nephrosis; nephrosonephritis (kidney tubules are affected along their entire length); cerebral edema; inflammation and edema of the lungs; myocarditis.

Toxic concentrations causing acute poisoning.

For humans, the threshold for odor perception is 0.0115 mg/l, and the concentration affecting the light sensitivity of the eye is 0.008 mg/l (Belkov). At 15 mg/l after 10 minutes headache, nausea, vomiting, increased heart rate; at 8 mg/l the same after 15 minutes, and at 2 mg/l - after 30 minutes. Workers with 8-hour exposure to a concentration of 1.2 mg/l experienced fatigue and drowsiness. When cleaning the floor Ch.U. (concentration in the air 1.6 mg/l), the worker felt a headache, dizziness after 15 minutes and was forced to leave work. The poisoning turned out to be fatal (the victim was an alcoholic). Mass poisoning has been reported during cleaning of evaporator coils on a ship (air concentration 190 mg/l). The victims, with the exception of one, survived. Exposure to a concentration of 50 mg/l can be fatal if inhaled for 1 hour. Severe poisoning with damage to the liver, kidneys and intestinal bleeding is known when working 2 shifts in a row in normal conditions washing instruments.

When ingesting 2-3 ml of Ch.U., poisoning may already occur; 30-50 ml lead to severe and fatal intoxication. Cases of mass poisoning have been described since 20 fatalities when ingesting a hair wash containing 1.4% Ch.U. (the rest is alcohol). Victims have bronchitis, pneumonia, bloody vomiting, diarrhea, liver and kidney damage. However, there is a known case of recovery after taking 220 ml of Ch. U. with developed anesthesia and severe kidney failure. Paraffin (vaseline) oil was used for gastric lavage.

In chronic poisoning, in relatively mild cases, the following is observed: fatigue, dizziness, headache, pain in the different parts body, muscle tremors, memory impairment, inertia, weight loss, cardiac disorders, irritation of the mucous membranes of the nose and throat, dysuric disorders. The most common complaints are abdominal pain, lack of appetite, and nausea. Enlargement and tenderness of the liver are detected; changes in motility, spasms of different parts of the intestine, bilirubinemia, etc.

On the skin, carbon tetrachloride can cause dermatitis, sometimes eczema, and urticaria. Irritates skin more than gasoline. When diving thumb hands in Ch, U, for 30 minutes after 7-10 minutes a feeling of cold and burning appears. After ersepoaicia there is erythema, which disappears after 1-2 hours. A case of polyneuritis as a result of constant contact of the C.U. with the skin during work is described. Penetrates in large quantities through burned skin; Poisoning is probably possible when extinguishing clothes that are burning on people using Ch.U.

Urgent Care.

In case of acute inhalation poisoning - fresh air, rest. Long-term inhalation of humidified oxygen using nasal catheters (continuous for the first 2-4 hours; subsequently 30-40 ppm with breaks of 10-15 minutes). Heart remedies: camphor (20%), caffeine (10%). cordiamine (25%) 1-2 ml subcutaneously; sedatives, strong sweet tea. Inject intravenously 20-30 ml of 40% glucose solution with 5 ml of 5% ascorbic acid, 10 ml of 10% calcium chloride solution. For hiccups and vomiting - intramuscularly 1-2 ml of a 2.5% solution of aminazine with 2 ml of a 1% solution of novocaine. In case of respiratory depression, inhale carbogen repeatedly for 5-10 minutes, intravenously 10-20 ml of a 0.5% solution of bemegride, subcutaneously 1 ml of a 10% solution of corazol. In the event of a sharp weakening (stopping) of breathing, artificial respiration using the “mouth to mouth” method with a transition to controlled respiration. In severe cases, immediate hospitalization in a resuscitation center.

When taking poison orally, thoroughly lavage the stomach through a tube, a universal antidote (TUM), 100-200 ml of petroleum jelly, followed by the administration of a saline laxative; cleansing the intestines to clean wash water (siphon enema); Bleeding (150-300 ml) followed by partial blood replacement. To enhance diuresis, inject into a vein 50-100 ml of 30% urea in a 10% glucose solution or 40 mg of Lasix. With the development of a collaptoid state, intravenously 0.5 ml of a 0.05% solution of strophanthin in 10-20 ml of a 20% glucose solution, or korglykon (0.5-1 ml of a 0.06% solution in 20 ml of a 40% glucose solution); according to indications - mezaton. In the future, to restore acid-base balance, intravenous drip administration of 300-500 ml of 4% sodium bicarbonate solution is performed. Vitamins B6 and C, lipoic acid, unithiol are recommended (5% solution intramuscularly, 5 ml 3-4 times a day on the first day, 2-3 times a day on the second and third days).

Contraindicated: sulfa drugs, adrenaline and chlorine-containing sleeping pills (chloral hydrate, etc.). Alcohol and fat consumption is not allowed!

Based on materials from the book: Harmful substances in industry. Handbook for chemists, engineers and doctors. Ed. 7th, lane and additional In three volumes. Volume I. Organic substances. Ed. honorable activities science prof. N.V. Lazareva and Dr. honey. Sciences E. N. Levina. L., "Chemistry", 1976.

UNION OF SOVIETSHIRISHI EDRESPUBLIK 07 S 07 S 19/06 RETENI RUSSKY and chaya upro-vestiye uch nshchenichennshitkob xo zoldnazol, ORS 12 general to ots-Khkhloushkinn and peSTATE CONITET OF THE USSR MADE INVENTIONS AND ABOUT 3 NRI TY DESCRIPTION I(71) Institute of Inorganic Chemistry.. , and electrochemistry of the Academy of Sciences of the Georgian SSR "Foreign literature", 1958, p. 393-396.2. Workshop on organic chemistry I., "IIR", 1979, p. 376 (prototype) , FOUR CARBON by drying with a desiccant and distillation, this is because, for the purpose of process technology and the degree of drying, a mixture of the formula CoK C 1 + Soy where 11- benz, 1,3- is used. tnadi1 - benz, 1,3-selenium at a mass ratio: Co K C 1 (25-30): in the presence of a mixture of 2.0-3.0 to the original fourth carbon, and the oregon stages are combined in time. 117295 The 2nd includes the boiling stage solvent at reflux for 18 hours using R O as a drying agent and subsequent 5th distillation on a column. The consumption of P05 per 1 liter of solvent is 25-30 g, and the water content in the target product is not lower than 0.00523.0 The disadvantages of the known method are complexity 1, the presence of two stages - drying and distillation and the duration of the process, which significantly complicates its technology, and also15 high water content in the target product. The purpose of the invention is to simplify the technology of the process and increase the degree of drying. - 20 This goal is achieved by the fact that according to the method of purifying carbon tetrachloride by drying over a desiccant and distillation, a mixture of cobalt complexes of the formula is used as a desiccant25 The invention relates to method for purifying carbon tetrachloride.Water is the main undesirable impurity of CC and therefore all purification methods, as a rule, include the stage of drying and distillation of the solvent.Drying and distillation are the final stages of the purification process of CC 1 and therefore removing water from CC 1 is an important task,CC 1 does not mix well with water (0.08%) and in many cases, distillation is sufficient for purification. Water is removed in the form of a azeotropic mixture, which boils at bb C and contains 95.9 solvents. A ternary azeotropic mixture of water (4.3%) and ethanol (9.7) boils at 61.8 C. When higher requirements are imposed on the purification of CC 1, distillation without first drying the solvent is unsuitable. There is a known method for purifying carbon tetrachloride, according to which CC 1 is pre-dried and then distilled on a column. Drying is carried out over CaC 1, followed by distillation and P 05 CC 1, dried over calcined CaC 1 and distilled from a flask with an effective reflux condenser in a water bath, and in some cases - from a quartz flask with a reflux condenser. When using SS 14, for thermochemical measurements, the solvent is twice subjected to fractional distillation on a column with a vacuum jacket, each discarding the first and last portions with a volume of a quarter of the total amount of distillate G 1. However, simple distillation of the solvent without the use of drying agents does not allow obtaining a solvent with a low water content. In methods based on the use of desiccants and subsequent distillation, preliminary long-term contact of the solvent with the desiccant is required, the choice of which for CC 1 is limited. Among desiccants, calcined CaC 1 is the most acceptable. It has been shown that 50CC 1 cannot be dried over sodium, since under these conditions an explosive mixture is formed. This cleaning method is time-consuming, has many steps and is ineffective. 55 The closest to the invention is the method of purifying CC 1, which is CoC C 1, + CoC C 1where d" benz, 1,3-thiadiaeol; k - benz, 1,3-selendiazole; with a mass ratio of Co KS 1Co K., C 1 25"30:1 and the total amount of the mixture is 2.0-3.0 wt. .L in relation to the original carbon tetrachloride, and the stages of drying and distillation are combined in time and space. The Co K C 1 and Co C C 1 complexes are prepared according to the well-known method 3.1. The essence of the proposed method is that cobalt complexes the indicated Pu K ligands disintegrate quantitatively in the presence of traces of water. These complexes are insoluble in all common solvents. In solvents with impurities of water, instead of the usual dissolution, the destruction of the complex takes place with the formation of a free ligand and hydrated cobalt ion. In solvents containing In the molecule there is a trivalent nitrogen atom, and a reaction of replacement of ligand molecules with solvent molecules occurs. Such solvents include amines, amides, itriles, as well as some heterocycles.g1117295 10 In solvents that do not contain a trivapentine nitrogen atom in the molecule, but contain impurities of water, in particular in CC 1, as a result of the reaction in the solution, decomposition products of the cobalt complex with sulfur- or selenium-containing diazoles. Using polarography, as well as UV and visible spectra of the resulting solutions, it was shown that there is no interaction between the ligand and the complexing agent in nitrogen-containing media or in media containing traces of water. Complexes of cobalt with aromatic diazoles can only be obtained in absolutely anhydrous media that do not contain a nitrogen atom. In all cases, when these complexes are introduced into solvents containing moisture impurities, the sum of the spectra of the ligand and the cobalt ion corresponds to the resulting spectrum, and the waves of the ligand and the cobalt ion are clearly recorded in the polarograms. 25 The decomposition reaction of cobalt complexes with the indicated diazoles under the influence of water molecules proceeds very quickly and the solvent takes on the color of the hydrated cobalt ion. Instant binding of traces of water by a desiccant (cobalt complexes occurs through the mechanism of hydrate formation (translation of the coordinated cobalt atom in the complex into a hydrated non-dissolved solution; therefore, coloring of the solvent in the color of hydrated cobalt ions can serve as a characteristic sign of the removal of water impurities from the solvent, It is known that the anhydrous solid has a pale blue color; di-, -tri-, tetra- and hexahydrates are violet, purple, red and red-brown, respectively.: The cobalt complex with diazoles is plates olive color, when added to CC 14, depending on the amount of water in 50, the solvent turns into one of the indicated colors of hydrated Co. The ability of cobaptate complexes with benz, 1,3-thia- and selendiazoles to decompose in the presence of traces of water depends on the nature of the ligand, more precisely on the nature of the key heteroatom in the ligand molecule. 4 Consequently, the effectiveness of the said complex as a desiccant also depends on nature of the heteroatom (R,Re) in the ligand and increases significantly when the sulfur atom is replaced by a selenium atom in the diazole heteroring. When the water content in CC 1 is very low, the most effective drying agent is a cobalt complex with benzo,1,3-selenium piaol. At a water content in the solvent in an amount not exceeding 0.013, a cobalt complex with benzene, 1,3-tidiaol can also serve as a drying agent. Consequently, a mixture of these complexes can serve as a desiccant in a wide range of water content in the solvent. For deep drying, CC 14 cobalt complex with benzene, 1,3-selendiaeol can be mixed as an admixture with a cobalt complex with benzo,1,3-thiadiazole, which will bind the bulk of water in the solvent. The required degree of purification of CC 1 in each specific case can be achieved by varying the proportion of the components of the mixture. However, in order for the composition to have maximum efficiency as a drying agent, it is necessary to use a minimum weight fraction of the cobalt complex with benzo,1,3-selendiaeol in the mixture. Thus, simultaneously with the effect of hydrate formation from an anhydrous cobalt complex, which is easily the basis of the proposed method, the composition of the drying mixture of cobalt complexes with aromatic diazoles is a characteristic feature this method purification of CC 14. Instant binding of traces of water by cobalt complexes based on the indicated diaeols when introduced into CC 14 eliminates the need for preliminary 18-hour refluxing of the solvent over RO. Therefore, the mixture of complexes can be introduced into the solvent directly at the distillation stage, thereby combining the stages of drying and distillation. The decomposition products of the complexes - the ligand aromatic diaeol and the hydrated cobalt ion have a much higher boiling point than CC, therefore, during distillation they cannot pass into the distillate. The latter is collected in a receiver with a set-.7295 ratio of cobalt complexes sbene, 1,3-thiadiaeol and bene, 1,3-selendiaeol. The results are shown in the table, swarming to prevent contact of the distillate with air. The excess mixture of cobalt complexes with diaeols, when introduced into CC 1, settles at the bottom of the flask of the distillation apparatus, in which 5 The rum purifying solvent retains the color of the hydrated cobalt ion until the end of the process. The water content in the distillate is determined by standard titration according to Fleur. Example 1. 300 ppm CC+ is added to the flask of a distillation apparatus, a mixture consisting of 10 g of cobolt complex with beneo, 1, 3-thiadiazole and O is added. 4 g cobalt complex with benzoate 2,1,3-selendiazole ( total mixtures of cobalt 23 complexes and distilled. A fraction with a boiling point of 76.5-77.0 C (" 200 ppm) is selected. The first fraction with a boiling point of up to 76.5 C 2 is discarded (30 ppm). The water content in the distillate is 0.00073, the transfer speed p 5 mp/min Duration t-O 3 0750 10: 15:1.0007 25 30 0.0005 0 Distillation process Thus, the invention simplifies the process technology by eliminating the stage of preliminary contact of the solvent30 with the desiccant of the drying and distillation stage combined in time and space, reducing the time required for cleaning CC 1 due to the rapid binding of traces of water in the solvent with a mixture of cobalt complexes with aromatic dia, aeols, and achieving the drying depth of CC 1, up to 0.00053 residual water, which increases the degree of drying is about the same, Sevnoarat, from 14 g of 2 1,3-ticobalone (generally added to the mixture is a complex of adiazolota with ben, the amount of frak "200 mp) e 0.0005 F Prodola Xs t is obtained at a fast pace Compiled by A. Arteedaktor N. Dzhugan Techred I. Astvlosh Correction V, Vutyaga Circulation 409 of the Dietary Committee of Acquisitions and Discovery, Zh, Raushskaya nsnoye d. 4/5 al PPP "Patent", g.uzh st. Proektnaya, 4 P P P, Patent Zak. 4 measures 2, 300 mp bu distillation a mixture consisting of cobalt with beneo and 0.4 g o,1,3-selendiae complex; the complex mixture is distilled, Select ip. up to 76.5-77 OS e water in distillation distillation 5 ppm process. measures 3-8. Process for example 2 with different degrees Order 7145/16 VNIIIII State Affairs Committee 113035, Ios

Application

3521715, 16.12.1982

INSTITUTE OF INORGANIC CHEMISTRY AND ELECTROCHEMISTRY AS GSSR

TSVENIASHVILI VLADIMIR SHALVOVICH, GAPRINDASHVILI VAKHTANG NIKOLAEVICH, MALASHKHIYA MARINA VALENTINOVNA, KHAVTASI NANULI SAMSONOVNA, BELENKAYA INGA ARSENEVNA

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Carbon tetrachloride purification method

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The invention relates to a method for purifying carbon tetrachloride from impurities of compounds containing carbon-hydrogen bonds and/or double bonds. According to the method, a solution of chlorine gas in liquid carbon tetrachloride is exposed to ultraviolet radiation in a reactor made of transparent material. The technical result is the purification of carbon tetrachloride from compounds containing double bonds and a carbon-hydrogen bond. The method provides the production of carbon tetrachloride containing less than 10 mg/ml of compounds with a carbon-hydrogen bond and double bonds. 1 n. and 6 salary files, 1 table.

The invention relates to a method for purifying technical carbon tetrachloride by exhaustive photochemical chlorination of impurities of compounds with hydrocarbons and double bonds with chlorine dissolved in carbon tetrachloride.

Purified carbon tetrachloride can be used by control, analytical and metrological services of chemical, petrochemical and other industries, sanitary and environmental supervision services, for the synthesis of organic compounds, as well as for other purposes.

There is a known method for purifying carbon tetrachloride from carbon disulfide, characterized in that, in order to simplify the process technology, the original carbon tetrachloride is treated with chlorine at a temperature of 10-80°C in the presence of a catalyst with a specific surface area of ​​10-300 m 2 /g.

The method makes it possible to purify carbon tetrachloride only from carbon disulfide.

There is a known method for purifying organochlorine products, in particular methylene chloride, chloroform, carbon tetrachloride and trichlorethylene, from tar and soot. The purification method involves introducing fuel with a boiling point of 150 to 500°C into organochlorine products before evaporation or rectification.

The method makes it possible to achieve purification of organochlorine products only from tar and soot.

There is a known method for purifying technical carbon tetrachloride from highly volatile impurities, based on the rectification separation of liquid mixtures.

The disadvantage of this method is its insufficient efficiency, since only reactive grade carbon tetrachloride is obtained: “pure”, “pure for analysis”, “chemically pure”, which contains a residual amount of impurities of compounds with hydrocarbon and double bonds, which is due to their high volatility, proximity boiling temperatures and the formation of azeotropic mixtures with the main component. The carbon tetrachloride obtained in this way cannot be used in analyzing the content of petroleum products in water and as a solvent for conducting research using the proton magnetic resonance method.

The objective of the invention is to develop an inexpensive and easily feasible method for purifying technical carbon tetrachloride from impurities of compounds with hydrocarbon and double bonds, making it possible to obtain carbon tetrachloride for use in analyzing the content of petroleum products in water and as a solvent for conducting research using the proton magnetic resonance method, as well as for other purposes.

The problem was solved by developing an easily feasible method for purifying technical carbon tetrachloride from impurities, based on the photochemical method of chlorination of compounds with hydrocarbon and double bonds with chlorine dissolved in carbon tetrachloride under the influence of ultraviolet irradiation.

The method is based on the production in solution of highly active radicals - chlorine atoms, formed when ultraviolet quanta of light are absorbed by chlorine molecules dissolved in carbon tetrachloride, which effectively destroy hydrocarbon bonds, resulting in a chain radical reaction to the formation of completely chlorinated products. At the same time, processes of complete chlorination of unsaturated compounds occur. Impurities that contaminate carbon tetrachloride and prevent its use in many studies, for example, when determining the content of petroleum products in water, are represented by saturated and unsaturated chlorinated derivatives of lower hydrocarbons. These are compounds with hydrocarbon and double bonds, mainly methane derivatives, mainly chloroform, as well as ethane derivatives, such as dichloroethane, trichloroethane, trichlorethylene, tetrachlorethylene.

A method for purifying technical carbon tetrachloride from impurities of compounds with hydrocarbon and double bonds is carried out as follows.

Chlorine gas is dissolved in carbon tetrachloride until its concentration in solution is approximately 0.2-2%. The resulting solution is irradiated with low-pressure mercury-quartz lamps. When irradiated in the UV radiation range of 250-400 nm for 1-20 minutes, impurities of methane chlorinated derivatives are converted into carbon tetrachloride, and ethane chlorinated derivatives into hexachloroethane. To remove excess chlorine and the resulting acids, carbon tetrachloride after photolysis is treated with a reducing deoxidizer, for example soda ash (Na 2 CO 3). Photochemical chlorination is carried out in a reactor made of transparent material, mainly quartz glass or Pyrex glass, which transmits UV radiation well in the range of 250-400 nm. A tetrachloride hydrocarbon is obtained containing impurities of compounds with hydrocarbon and double bonds of no more than 10 mg/l, determined by the IKN method used to measure the mass concentration of petroleum products in hydrocarbon tetrachloride. The hydrocarbon tetrachloride purified in this way contains pentachloroethane and hexachloroethane, and their content depends on the content of ethane chloride derivatives with hydrocarbon and double bonds in the original technical carbon tetrachloride. Such purified carbon tetrachloride can be used in determining the content of petroleum products in water, since the presence of pentachloroethane and hexachloroethane does not affect the results of the analysis. To obtain carbon tetrachloride of special purity, an additional stage of separating carbon tetrachloride from pentachloroethane and hexachloroethane by conventional distillation is carried out, which remain in the bottoms. The photochemical chlorination process can be carried out in batch or flow-circulation mode.

Example 1. 0.1 g of chlorine is dissolved in 32 g of technical carbon tetrachloride. The resulting solution in a quartz glass cuvette is irradiated with light from a DRT-250 mercury lamp for 15 minutes. After irradiation with UV light, the resulting product was treated with anhydrous sodium carbonate (approximately 2 g) to remove excess chlorine, acids and water formed. Based on chromatographic analysis of a carbon tetrachloride sample before and after purification, it was found that the amount of impurities determined by the IKN method was reduced from 217 to 10.2. The mass fraction of pentachloroethane and hexachloroethane was 0.153% and 1.340%, respectively.

Example 2. 0.1 g of chlorine is dissolved in 32 g of technical carbon tetrachloride. The resulting solution in a Pyrex glass cuvette is irradiated with light from a DRT-1000 mercury lamp for 5 minutes. After irradiation with UV light, the resulting product was treated with anhydrous sodium carbonate (approximately 2 g) to remove excess chlorine, acids and water formed. Based on chromatographic analysis of a carbon tetrachloride sample before and after purification, it was found that the amount of impurities determined by the IKN method was reduced from 217 to 5.7. The mass fraction of pentachloroethane and hexachloroethane was 0.011% and 1.628%, respectively.

Example 3. Purified carbon tetrachloride, obtained as in example 2, is additionally subjected to distillation at the boiling point of carbon tetrachloride and carbon tetrachloride is obtained in the distillate with a content of the main component of 99.987%, the number of impurities determined by the IKN method was reduced from 5.7 to 2, 3. A mixture of pentachloroethane and hexachloroethane remains in the bottoms.

Example 4. Carbon tetrachloride is saturated with chlorine gas to a concentration of 0.6% in a mixer. Then, at a speed of 0.5 l/min, it enters a cylindrical photoreactor made of Pyrex glass, cooled by running water, illuminated by a DRT-1000 mercury lamp located along its axis. From the photoreactor, carbon tetrachloride passes to a filter column, where it passes through anhydrous sodium carbonate to remove excess chlorine, as well as the resulting acids and water. Based on chromatographic analysis of a carbon tetrachloride sample before and after purification, it was found that the amount of impurities determined by the IKN method was reduced from 217 to 12.3. The mass fraction of pentachloroethane and hexachloroethane was 0.322% and 1.311%, respectively.

Consequently, when purifying hydrocarbon tetrachloride in this way, carbon tetrachloride is obtained containing impurities of compounds with hydrocarbon and double bonds, determined by the IKN method, no more than 10 mg/l. The admixture of pentachloroethane and hexachloroethane present in purified carbon tetrachloride allows it to be used in determining the content of petroleum products in water. Additional distillation produces carbon tetrachloride of “special purity.”

The results of purification of carbon tetrachloride are presented in the table.

INFORMATION SOURCES

1. SU No. 686274.

2. RU No. 2051887.

3. RU No. 2241513.

4. GOST R51797-2001.

1. A method for purifying carbon tetrachloride, characterized in that impurities of compounds with hydrocarbon and double bonds are removed by the method of exhaustive photochemical chlorination with chlorine dissolved in carbon tetrachloride in a reactor made of transparent material under the influence of ultraviolet irradiation, thereby obtaining carbon tetrachloride for analysis determination of the content of petroleum products in water, containing no more than 10 mg/l of compounds with hydrocarbon and double bonds.

2. The method according to claim 1, characterized in that carbon tetrachloride is obtained for research using the proton magnetic resonance method.