Aromatic hydrocarbons are an important part of the cyclic series of organic compounds. The simplest representative of such hydrocarbons is benzene. The formula of this substance not only distinguished it from a number of other hydrocarbons, but also gave impetus to the development of a new direction in organic chemistry.

Discovery of aromatic hydrocarbons

Aromatic hydrocarbons were discovered in the early 19th century. In those days, the most common fuel for street lighting was luminous gas. From its condensate, the great English physicist Michael Faraday isolated three grams of an oily substance in 1825, described its properties in detail and named it: carbureted hydrogen. In 1834, a German scientist, chemist Mitscherlich, heating benzoic acid with lime, obtained benzene. The formula by which this reaction proceeded is presented below:

C6 H5 COOH + CaO fusion C6 H6 + CaCO3.

At that time, the rare benzoic acid was obtained from the benzoic resin, which some tropical plants can secrete. In 1845, a new compound was discovered in coal tar, which was a readily available raw material for the production of a new substance on an industrial scale. Another source of benzene is oil from some fields. To meet the needs of industrial enterprises in benzene, it is also obtained by aromatization of certain groups of acyclic hydrocarbons in petroleum.

The modern version of the name was proposed by the German scientist Liebig. The root of the word "benzene" should be found in Arabic languages- there it is translated as "incense".

Physical properties of benzene

Benzene is a colorless liquid with a specific odor. This substance boils at a temperature of 80.1 ° C, solidifies at 5.5 ° C and turns into a white crystalline powder. Benzene practically does not conduct heat and electricity, it is poorly soluble in water and well in various oils. The aromatic properties of benzene reflect the essence of its internal structure: a relatively stable benzene nucleus and an undefined composition.

Chemical classification of benzene

Benzene and its homologues, toluene and ethylbenzene, are an aromatic series of cyclic hydrocarbons. The structure of each of these substances contains a common structure called the benzene ring. The structure of each of the above substances contains a special cyclic grouping created by six carbon atoms. It is called the benzene aromatic nucleus.

Discovery history

The establishment of the internal structure of benzene took several decades. The basic principles of the structure (ring model) were proposed in 1865 by the chemist A. Kekule. According to the legend, a German scientist saw the formula for this element in a dream. Later, a simplified spelling of the structure of a substance called benzene was proposed. The formula of this substance is a hexagon. The symbols for carbon and hydrogen, which are to be located at the corners of the hexagon, are omitted. Thus, a simple regular hexagon is obtained with alternating single and double lines on the sides. The general formula of benzene is shown in the figure below.

Aromatic hydrocarbons and benzene

The chemical formula of this element suggests that addition reactions are not typical for benzene. For him, as for other elements of the aromatic series, reactions of substitution of hydrogen atoms in the benzene ring are typical.

Sulfonation reaction

By ensuring the interaction of concentrated sulfuric acid and benzene, increasing the reaction temperature, you can get benzosulfonic acid and water. The structural formula of benzene in this reaction is as follows:

Halogenation reaction

Bromine or chromium reacts with benzene in the presence of a catalyst. In this case, halogen derivatives are obtained. But the nitration reaction takes place using concentrated nitric acid. The end result of the reaction is a nitrogenous compound:

With the help of nitriding, a well-known explosive is obtained - TNT, or trinitotoluene. Few people know that benzene is the basis of tol. Many other nitro compounds based on a benzene ring can also be used as explosives.

Electronic formula of benzene

The standard formula of a benzene ring does not quite accurately reflect the internal structure of benzene. According to her, benzene must have three localized p-bonds, each of which must interact with two carbon atoms. But, as experience shows, benzene does not possess ordinary double bonds. The molecular formula of benzene makes it possible to see that all bonds in the benzene ring are equivalent. Each of them has a length of about 0.140 nm, which is an intermediate value between the length of the standard single bond (0.154 nm) and the double ethylene bond (0.134 nm). The structural formula of benzene, depicted with alternating bonds, is imperfect. More plausible is a three-dimensional model of benzene, which looks like the one shown in the picture below.

Each of the atoms of the benzene ring is in the sp 2 -hybridization state. It spends three valence electrons for the formation of sigma bonds. These electrons span two adjacent carbohydrate atoms and one hydrogen atom. In this case, both electrons and communication C-C, H-H are in the same plane.

The fourth valence electron forms a cloud in the form of a three-dimensional figure, located perpendicular to the plane of the benzene ring. Each such electron cloud overlaps above the plane of the benzene ring and immediately below it with clouds of two adjacent carbon atoms.

The density of the n-electron clouds of this substance is evenly distributed between all carbon bonds. In this way, a single annular electron cloud is formed. In general chemistry, this structure is called the aromatic electronic sextet.

Equivalence of internal bonds of benzene

It is the equivalence of all the faces of the hexagon that explains the evenness of aromatic bonds, which determine the characteristic chemical and physical properties that benzene possesses. The formula for the uniform distribution of the n-electron cloud and the equivalence of all its internal connections are shown below.

As you can see, instead of alternating single and double lines, the internal structure is depicted as a circle.

The essence of the internal structure of benzene provides a key to understanding the internal structure of cyclic hydrocarbons and expands the possibilities of practical application of these substances.

Benzene is one of the most toxic substances that surrounds us everywhere. Smog, industrial emissions - everyone knows about their health risks. But not everyone understands that this is not the main threat. Much more dangerous is the constant stay in an atmosphere poisoned with benzene. And it is very difficult to avoid this.

Where is benzene found

Industry cannot exist without benzene. A flammable liquid with a slight sweetish odor having the formula C 6 H 6 - perhaps the most basic Chemical substance for many industrial sectors. It is used:

• For the production of cosmetics, perfumery, aniline dyes.
• Rubber, plastic, many others synthetic materials, - all of them basically contain aromatic hydrocarbons, which are obtained from benzene.
• The same aromatic hydrocarbons are used in the production of drugs, rubber, explosives, and artificial leather.
• The operation of benzene coke plants is also inconceivable without the use of C 6 H 6.
• The composition of paraffin candles (regular and aromatic) includes benzene.
• All waterproof fabrics are impregnated with benzene-based compounds.

This liquid is an excellent solvent. Sometimes benzene is even called "organic water", which can dissolve anything. That is why benzene is used for the following purposes:

• to isolate alkaloids from plants;
• to isolate phosphorus and fats from bones, meat and nuts;
• to convert iodine into useful solutions;
• to dissolve rubber adhesives, rubber, any other paints and varnishes.

With benzene, dry cleaners remove the most difficult stains. And C 6 H 6 is also a luminous gas, welding reagents, alcohol and many other products, without which life modern man impossible.

Motorists know: it was benzene that gave its name to automobile fuel, it is with its help that you can raise the octane number and reduce the fuel's ability to ignite spontaneously.

There are hundreds of other industries that use C 6 H 6. It is the widespread occurrence of this substance that makes it especially dangerous.

Why is benzene dangerous?

C 6 H 6 is a substance so dangerous that:

• The International Agency for the Study of Cancer, recognized it as one of the most powerful carcinogens.
• In Geneva, back in 1971, the "Benzene Convention" was adopted, which calls for limiting the use of the substance, because it poses a mortal threat to humanity.

Nevertheless, today in the industry not only does not reduce, but increases the use of this substance.

So why is benzene dangerous?

• A liquid with a sweetish odor evaporates strongly. Mixing with oxygen in the air, it can form a powerful explosive mixture.
• Vapors C 6 H 6 are heavier than air. Accumulating from the lower part of the room, they can cause severe poisoning.
• When burning, all materials containing benzene derivatives emit a huge amount of soot and burning. It is because of them, and not because of open fires, that people most often die in fires.

Naturally, acute benzene poisoning can lead to almost instant death, which will be preceded by the following symptoms:

• increased heart rate;
• a sharp drop in pressure;
• nausea;
• dizziness or sharp headaches;
• excitement, which is quickly replaced by sheer apathy. Sometimes it is so strong that a person is not able to leave the scene of the accident;
• convulsions;
• loss of consciousness.

Even more dangerous is chronic poisoning of the body with benzene. It is possible in situations where people have to stay for a long time in rooms with a concentration of C 6 H 6 exceeding the MPC, but not causing acute poisoning. Usually, such a threat hangs over workers in industrial enterprises, garages, and motorists.

. Benzene plays an extremely important role in a variety of chemical industries. industry. For the first time, benzene was discovered in light fractions of coal tar by Faraday in 1825.The special properties of benzene and its derivatives were expressed in the structure formula proposed in 1865 by Kekule, in the form of a closed chain of six carbon atoms, at which there is one hydrogen atom ... However, such a structure is not entirely consistent with the properties of various substances obtained from benzene, and therefore, over time, various researchers have made some modifications to the formula for the structure of benzene concerning Ch. arr. distribution of affinity forces within the carbon cycle. The main source of benzene production is the products obtained during the processing coal for coke and light gas. V recent times Attempts were made to obtain benzene from oil by pyrogenetic decomposition, but they have not yet led to the development of sufficiently cost-effective methods. From the gases of coke ovens, which contain the main mass of benzene, it is extracted by various solvents or adsorbed by solids. Usually, a fraction of coal tar is used for dissolution, which gives at least 80% of distillate in the range of 200-300 °; sometimes instead of coal oil, oil strips, known as diesel oil, are used. With a good oil, up to 98% of all benzene contained in it can be extracted from gas.

Coke oven gas, passing through refrigerators, gum separators and ammonia washers, having a temperature of no higher than 20 °, enters the scrubber, where it is washed with an absorbent oil that dissolves benzene. The scrubbers are high round towers, inside of which a packing is made, which contributes to a closer mixing of the gas with the absorption oil. The oil, saturated with benzene with a content of the latter of about 3%, goes for regeneration to the columns, where the so-called crude benzene, which has up to 65% of pure benzene, is distilled off. The oil, freed from benzene, is cooled and goes back to the scrubber to flush the gas. Crude benzene contains a large number of different carbonaceous compounds and varies in composition. Fluctuations in the composition depending on the nature of production can be seen from the following table:

In addition to these substances, naphthalene, cumene, thiotolene, phenol, cresols, pyridine, coumarones are also part of the crude benzene. At the Donbass factories, the content of pure benzene in the crude product averages about 52%. To obtain pure benzene, the crude product is purified and rectified. The first rectification gives 90% benzene, which then goes to purification and further rectification to obtain pure benzene. Cleaning consists in sequential washing of benzene with a solution of alkali, acid and water. If benzene contains bases and phenols, then first it is washed with dilute sulfuric acid, thereby removing the bases, and the alkali then dissolves all acidic substances. Carbon disulfide, thiophene, unsaturated aliphatic hydrocarbons are removed by treatment with strong sulfuric acid 60-66 ° Вè, which sulfonates and resins all unsaturated and sulfur compounds, converting them into soluble and easily washed out substances with alkali. Cleaning is carried out in special apparatuses - stirrers, equipped inside with devices for mechanical stirring of the liquid in order to ensure the fastest and most complete cleaning possible. Benzene, freed from impurities and sulfur compounds (for this purpose, it is necessary to resort to repeated acid treatment), goes to the final rectification to obtain a pure product. Perfectly pure benzene - colorless, transparent, easily mobile, very flammable liquid which solidifies at 5.483 ° (hydrogen thermometer) and boils at 80.08 ° (760 mm Hg). The specific gravity of benzene D 25 = 0.87345, D 4 15.5 = 0.8845, it changes with temperature; according to Copp, v t = 1 + 0.001171626t + 0.00000127755t 2 + 0.00000080648t 3. Refractive index n D 8.2 = 1.50808. Specific volume at 20 ° - 0.67171. Specific heat of pure benzene, according to Treen (Tgehin) at 16.2 ° - 0.402, 20.2 ° - 0.412, 30.0 ° - 0.419, 42.8 ° - 0.429, 50.4 ° - 0.437, 58.1 ° - 0.449; specific heat commercial benzene, purified by freezing, at 18.3 ° - 0.414, 22.7 ° - 0.418, 31.8 ° - 0.425, 40.3 ° - 0.439; 52.0 ° - 0.452.

Heat of combustion at constant volume 10.014 Cal. Benzene at 22 ° C is soluble in water in the amount of 0.082 volumes per 100 volumes of water. Water dissolves in benzene depending on temperature as follows (in %%):

Benzene is an excellent solvent for fats, resins, rubber and other organic compounds.

Chemical properties... Benzene is difficult to react with substances that interact with ethylene and its derivatives. In the presence of catalysts - nickel, palladium or platinum - benzene adds 6 hydrogen atoms and transforms into hexohydrobenzene or hexamethylene. The hydrogen atoms of benzene can be replaced by halogens to form the corresponding halogen derivatives. Strong sulfuric and nitric acids, when exposed to benzene, give the corresponding sulfo- and nitro derivatives. Commercial benzene grades are usually not pure benzene, but also contain toluene and xylene in varying amounts... According to Kramer and Shpilker, the following grades of commercial benzene are distinguished (depending on the% content of substances in it, distilled off to 100 °):

The applications for benzene are very diverse. Large quantities of benzene are currently used as an admixture to motor gasoline, which significantly improves the quality of the latter. In England, the National Benzol Association has the following requirements for motor benzene: specific gravity 0.870-0.885; during distillation, benzene should give up to 100 ° - 75%, 120 ° - 90%, 125 ° - 100%; the sulfur content in it should not exceed 0.4%; benzene must not contain water; degree of purification: when shaking 90 cm 3 of benzene with 10 cm 3 of 90% H 2 SO 4 within 5 minutes, the acid should turn into a color no darker than light brown; benzene should not contain acids, alkalis and hydrogen sulfide; must freeze at least -14 °.

Benzene is used as a solvent and for extraction purposes in various industries: for the preparation of varnishes and linoleum, for degreasing bones, for the extraction of wax and rosin, for dry cleaning various materials... Benzene is one of the most commonly used solvents in rubber factories. It also serves as a starting material for the preparation of dyes, explosives and fragrances, pharmaceuticals and photographic preparations. Huge amounts of benzene are processed into nitro- and dinitrobenzene, from which aniline, nitroaniline and phenylenediamine are obtained by reduction - important products technologies of organic substances serving Ch. way the starting material in the manufacture of a variety of different aniline dyes. Mono- and disulfonic acids are prepared from benzene by sulfonation, which are further processed into phenol and resorcinol.

In the pre-war period, the production of benzene in Russia was extremely poorly developed. With the outbreak of the war and, consequently, with an increase in the need for benzene, which was used to prepare various explosives, it was hastily necessary to organize benzene coke plants. The systematic and successful development of the benzene industry began with the establishment of the Joint-Stock Company "Coke-benzene" in the USSR, and at present the amount of benzene produced annually significantly exceeds the most productive years of the pre-war period.

Occupational benzene poisoning... Benzene is one of the most potent occupational poisons. Poisoning of workers with benzene is possible: in the benzene-coke production, during the distillation of coal tar; at chemical and pharmaceutical plants in the production of various aromatic substances; in the production of various organic paints; in the production of explosives; when extracting fats from bones and coconuts; in glue factories, where benzene is used as a solvent for resins, varnishes, fats, iodine, phosphorus and sulfur; v rubber production; in the manufacture of waterproof fabrics, linoleum, celluloid; when painting various objects with rapidly drying paints and varnishes (in particular, airplane wings); when carburation of lamp and water gas; in chemical dyeing houses and when cleaning fabrics, clothes, etc. from fats; when servicing engines internal combustion, etc. Recently, in the West, many patented factories containing benzene have been produced (varnishes, paints, cleaning compounds different subjects) under a variety of names and causing serious poisoning of workers.

Benzene penetrates into the body of hl. way through the respiratory tract and through the lungs enters the bloodstream. However, benzene can also be absorbed through intact skin. Benzene is much more toxic than gasoline (according to Lehman and Kravkov - 4 times, according to Kon-Abrest - 10 times). The content in the air of 10 mg of benzene vapor per 1 liter (by volume 3-4 hours per 1000 hours) already causes unpleasant sensations; the presence of 20-30 mg of benzene in 1 liter of air usually causes loss of consciousness for several hours. Sometimes, however, even 0.001 benzene by volume in the air caused death. In order to prevent the slow effect on workers of prolonged inhalation of benzene vapors, their content in the working atmosphere should not be higher than 1: 10,000, or approximately 0.25 mg / l (although, according to a special American commission that published its report in 1927 ., even under these conditions it is impossible to completely avoid the effects of benzene on the body).

Benzene poisoning can be acute and chronic. In recent years, a number of deaths have been published in the medical literature, either immediately after a single inhalation of a significant amount of benzene vapor, or as a result of an acute illness after a short period of operation in an atmosphere with a significant amount of benzene vapor in the air. Immediate death usually occurs when working in insufficiently ventilated cisterns, tanks, etc. containers, as well as when vessels or pipes are ruptured and when equipment malfunctions are not noticed. Serious illnesses, often ending in death, usually occur with insufficient room volume, lack of ventilation, and especially when high temperature premises. Acute poisoning that does not end in immediate death, when inhaled in large doses, causes severe changes in the central nervous system: tremors, convulsions, severe paleness, sensory disturbances, fainting, and also often malignant anemia (especially affecting women). Mild cases cause dizziness, headache, tinnitus, vomiting. For the most part, a state of intoxication and general euphoria soon sets in, as a result of which the poisoned person loses the correct perception of what is happening, does not notice the danger, does not leave the place where the vapors are released and, in the absence of outside help, may become a victim of further poisoning. In chronic poisoning that lasts for months and even years, in addition to the nervous system, the circulatory and hematopoietic organs are primarily affected, as a result of which, in addition to severe anemia, numerous small hemorrhages appear, as in the mucous membranes of various internal organs and in the skin. As a result - the so-called. "Spotted disease" and scurvy-like changes in the mucous membrane in the mouth. Women usually have severe uterine bleeding. Recovery is rare and even in favorable cases is very delayed. Such a severe effect of benzene is explained by the fact that it is a strong poison that acts on the protoplasm of all cells of the body and on the main oxidative processes. The measures for the prevention of benzene poisoning are basically the same as for gasoline poisoning. It should be added that wherever possible, benzene should be replaced with much less toxic xylene, toluene, carbon tetrachloride or gasoline, and women should not be allowed to work with benzene.

Benzene and its negative effects on the body have long been a topic for study among physicians and researchers. Experts have proven that, despite its widespread use, such a substance carries a toxic effect. Due to the fact that benzene vapor is not visible, some downplay its danger, but in fact, such a chemical compound can lead to irreversible consequences in any living organism.

General information

Before studying the consequences of poisoning with this liquid, it is necessary to understand what benzene is in the context of the chemical industry. It is a hydrocarbon that belongs to the category of aromatic compounds. Its characteristic features are:

• colorlessness,
• transparency,
• ease of mobility,
• specific aroma;
• rapid evaporation provided that the temperature is kept within room temperature.

In this case, the product of the chemical industry is a liquid that strongly refracts light. It boils when the temperature reaches 80.5 degrees, and in the cold it turns into a crystal-like mass, which begins to melt already at six degrees of heat.

The compound dissolves easily in typical solvents such as chloroform, alcohol and ether. This rule does not apply except to water. It is often used as a solvent for fats, various resins, or oils. Moreover, its composition is quite easily flammable, smoking heavily.

According to environmental studies, this compound is considered one of the most toxic, which is found everywhere in humans. Thanks for this should be the large-scale emissions of industrial enterprises for various purposes, as well as the smog periodically covering large cities.

Scope of use

Modern industry can no longer do without this toxic product of the chemical industry. It is not yet possible to replace С 6 Н 6 (benzene formula) in all traditional areas of its application, therefore the ecology continues to suffer from its influence.

It is impossible to answer in a few words the question of where such a dangerous compound is used, since the scope of its use is expanding every year. Today, specialists in the following areas most often resort to his help:

• cosmetics,
• perfumery,
• dyes,
• synthetic materials such as rubber, plastics,
• pharmaceuticals,
• light industry,
• explosives,
• coke,
• paraffin.

The product is used to create artificial leather, as well as to improve fabrics that have received a waterproof structure.

In addition, the quality of the liquid, which provides for the functions of dissolution, made it an active assistant, if necessary, to divide or isolate:

• alkaloids from various plants;
• fat from meat products (up to the extraction of phosphorus from bones), nuts;
• adhesives based on rubber and other paints and varnishes.

Benzene is sometimes used in pharmaceuticals to convert iodine into medicinal solutions. And motorists took it into service after the method of raising the octane number in the production of transport fuel began to be in demand in the world. It also reduces the self-ignition characteristic of a fuel resource.

In everyday life, the compound is an important part of the dry cleaning procedure in specialized institutions. It makes it much easier to remove difficult stains on almost any fabric.

Hazard factors

Saving many branches of the industry, the C 6 H 6 formula is so dangerous that it was included in the list of the strongest carcinogens that accompany the formation of cancerous tumors of various organs. Doctors began to sound the alarm for a long time, which resulted in the promulgation of a specially created convention within the framework of the Geneva conference back in 1971. Even then, people knew that in addition to being useful, the product carries a huge mortal threat.

The main dangers that plague a person dealing with benzene are:

• the formation of an explosive mixture. Since this liquid evaporates almost instantly, it is able to quickly mix with oxygen in the environment, turning into a compound that threatens life and health.
• poisoning. It is caused by the fact that benzene vapors are much heavier than air, they settle at the bottom of the room, which leads to intoxication of people in the same place.
• soot and fumes. Despite the stereotype that people die in fires due to open flames, this is not entirely true. More often than not, a person becomes a victim of the release of side effects of a chemical when it burns.

On average, on a sunny day, up to 4000 mg of benzene vapor gets into the car interior, where the temperature is maintained at least 16 degrees Celsius, from the gas tank of an ordinary car. If you add to this the fumes from the upholstery and other elements, you get an impressive dose of toxins. That is why experts recommend that you first ventilate the cabin, and then turn on the air conditioner and go about your business.

Action on humans

Considering benzene and its negative effects on the body, one should first deal with potential risk groups. Most often these are the people who work in the factory. Also, the list includes all those who are engaged in its regular supply, or are responsible for its storage, processed products.

In addition, the list includes:

• washers of tanks in which the product was transported;
• laboratory assistants at oil refining stations;
• pump repair workers;
• victims of fires, where a significant content of the product was released (often these are plastic products, rubber products).

Benzopropylene enters the body together with the air in the form of vapors. It is this method that is considered the most frequent in case of poisoning with such a substance. In second place is skin contact.

Despite its danger, short-term inhalation of the vapors will not cause serious harm. But with prolonged contact with a toxic environment or contact with a concentration of doses exceeding the norm, this may result in the penetration of the constituents of an artificially created product into the blood. It is excreted through respiration, through the kidneys, or in breast milk if the victim was a woman during lactation.

If skin contact occurs, the patient will:

• feel dry;
• cracks will appear;
• the affected area turns red;
• itching will begin;
• swelling or blister-type rashes will appear.

Poisoning can be schematically divided into two broad groups:

• spicy,
• chronic.

In the first case, most of the respiratory system is affected, as well as the brain and adrenal glands. In the second scenario, the hematopoietic system always suffers more strongly.

If the impact on the body is made on a regular basis, then everything can end:

• gene mutations;
• malfunction of the reproductive organs;
• harm to the fetus (meaning the effect on pregnant women).

In addition, additional side effects periodic convulsions may appear, as well as a violation of the vitamin balance of group B.

Acute poisoning

Acute benzene intoxication is much less common than chronic intoxication, but this does not diminish its negative impact. Often it occurs due to an accident or a man-made accident, which ends with the ingress of a dose into the body that exceeds the permitted dozens of times.

The general symptoms are as follows:

• disruption of the nervous system, which is expressed in lethargy, vertigo, headache, loss of oneself in space.
• a drop in body temperature and increased respiration, followed by a weakening of the pulse.
• pallor of the skin.

If nothing is done after the expression of such signs, then the patient may have seizures, and he will fall into a coma. That is why it is extremely important to see a doctor on time by calling an ambulance.

To alleviate the patient's condition before the arrival of doctors, you need:

• take it out to fresh air;
• if there was contact with the skin, rinse the affected area with a solution of ordinary baking soda;
• if necessary, perform chest compressions and artificial respiration.

Chronic poisoning

The influence of hydrocarbons on the human body is most often expressed in chronic poisoning. This happens due to prolonged contact with small doses of the compound. Only an experienced expert can suspect its manifestation in a patient on the basis of a thorough diagnosis, which includes the study of the situation of the sick at home, at work.

The main blow that benzene inflicts in this case is a negative effect first on the bone marrow, and then nervous system... The classic manifestations of the chronic course of poisoning are usually called:

• increased fatigue,
• constant lethargy
• insomnia
• nervousness,
• frequent headaches
• dizziness.

The picture ends with bone pain, nausea, vomiting. In case of accidental injury (even with regular brushing of teeth), the blood does not clot for a long time. The picture of anemia is confirmed by hair loss, pallor of the skin, brittle nails. A person feels a decrease in physical as well as mental performance.

To counter this and more serious consequences at further stages of poisoning development, it is necessary first of all to find out where the benzene is contained. After finding a toxic source of problems, you need to stop contact with him.

BENZENE

Benzene (C6H6) is an organic chemical compound, a colorless liquid with a pleasant sweetish odor. Aromatic hydrocarbon. Benzene is a part of gasoline, is widely used in industry, is a feedstock for the production of drugs, various plastics, synthetic rubber, dyes. Although benzene is found in crude oil, it is synthesized commercially from other components.

Biological action

With a short inhalation of benzene vapors, immediate poisoning does not occur, therefore, until recently, the procedure for working with benzene was not particularly regulated. In large doses, benzene causes nausea and dizziness, and in some severe cases poisoning can be fatal. Benzene vapors can penetrate intact skin. If the human body is exposed to small amounts of benzene for a long time, the consequences can also be very serious. In this case, chronic benzene poisoning can cause leukemia (blood cancer) and anemia (lack of hemoglobin in the blood). Toxic, strong carcinogen.

Application

Benzene is one of the ten most important substances in the chemical industry.

Most of the resulting benzene is used for the synthesis of other products:

• about 50% of benzene is converted to ethylbenzene (benzene alkylation with ethylene);

• about 25% of benzene is converted to cumene (alkylation of benzene with propylene);

• about 10-15% of benzene is hydrogenated to cyclohexane;

• about 10% of benzene is consumed in the production of nitrobenzene;

• 2-3% of benzene is converted to linear alkylbenzenes;

• approximately 1% of benzene is used for the synthesis of chlorobenzene.

In much smaller amounts, benzene is used for the synthesis of some other compounds. Occasionally and in extreme cases, due to its high toxicity, benzene is used as a solvent. In addition, benzene is found in gasoline. Due to its high toxicity, its content is limited to 1% by the new standards.

Benzene derivatives

Ethylbenzene

Ethylbenzene is an organic substance of the hydrocarbon class.

Properties

Colorless liquid; almost insoluble in water, soluble in alcohol, benzene, ether, carbon tetrachloride.

Receiving

Ethylbenzene is found in petroleum and coal tar. In industry, they are obtained mainly from benzene and ethylene (according to the Friedel-Crafts reaction). The second most important method is the separation of reforming products from the C8 fraction.

Application

When ethylbenzene vapor is passed over the catalysts, styrene is formed, which is a raw material for the production of important industrial products - some types of plastics (see Polystyrene) and synthetic rubbers. Ethylbenzene is also used in organic synthesis, for example, to obtain acetophenone by liquid-phase catalytic oxidation, as a solvent and a component of high-octane gasolines.

Styrene C8H8 (phenylethylene, vinylbenzene) is a colorless liquid with a specific odor. Practically insoluble in water, well soluble in organic solvents, good solvent for polymers.

Receiving

Most of styrene (about 85%) in industry is obtained by dehydrogenation of ethylbenzene at a temperature of 600-650 ° C, atmospheric pressure and dilution with superheated steam by 3-10 times. Iron-chromium oxide catalysts with the addition of potassium carbonate are used.

Styrene is used almost exclusively for the production of polymers. Numerous styrene-based polymers include polystyrene, styrene-modified polyesters, ABS (acrylonitrile butadiene styrene) and SAN (styrene acrylonitrile) plastics.

Polystyrene

Polystyrene

Polystyrene - a polymerization product of styrene (vinyl benzene) belongs to the thermoplastic class polymers.

Has a chemical formula of the form: [-CH2-C (C6H5) H-] n-

Industrial production of polystyrene is based on radical polymerization of styrene. There are 3 main ways to obtain it:

• Emulsion (PSE),

• Suspension (PSS),

• Block or obtained in bulk (PSM).

Application

Application

The widespread use of polystyrene (PS) and plastics based on it is based on its low cost, ease of processing and a huge range of different brands. Most wide application(more than 60% of the production of polystyrene plastics) received impact-resistant polystyrenes, which are copolymers of styrene with butadiene and styrene-butadiene rubber. Numerous other modifications of styrene copolymers have been created.

Main processing methods: extrusion, injection molding. The processing temperature range is within 190-240 ° C. A wide range of products is produced from polystyrene, which are primarily used in the domestic sphere of human activity ( disposable tableware, packaging, toys, etc.), and construction industry (thermal insulation boards, permanent formwork, sandwich panels), facing and decorative materials (ceiling molding, ceiling decorative tiles, polystyrene sound-absorbing elements, adhesive bases, polymer concentrates), medical direction (parts of blood transfusion systems, Petri dishes, auxiliary disposable instruments).

Foaming polystyrene after high-temperature temperature treatment with water or steam can be used as a filter material (filtering nozzle) in column filters for water treatment and wastewater treatment.

High electrical performance of polystyrene in the field of ultrahigh frequencies makes it possible to use it in the production of: dielectric antennas, coaxial cable supports. Thin films (up to 100 microns) can be obtained, and in a mixture with copolymers (styrene-butadiene-styrene) up to 20 microns, which are also successfully used in the packaging and confectionery industries, as well as in the production of capacitors.

High-impact polystyrene and its modifications are widely used in the field of household appliances and electronics (housing elements of household appliances).

Kumol - isopropylbenzene C6H5CH (CH3) 2, aromatic organic compound, colorless flammable liquid.

Physicochemical properties

Colorless flammable liquid, practically insoluble in water (less than 0.01%), mixes up with alcohol, ether, benzene.

Method of obtaining

Liquid-phase (catalyst: aluminum (III) chloride) or vapor-phase (catalyst: zeolites, phosphoric acid on diatomaceous earth) alkylation of benzene with propylene.

Application

Cumene is an intermediate product in the production of phenol and acetone by one of the industrial methods.

Decomposition by-products are α-methylstyrene, acetophenone, dimethylphenylcarbinol.

Acetone (dimethylketone, systematic name: propanone-2) is the simplest representative of ketones. Formula: CH3-C (O) -CH3. Colorless volatile liquid with a characteristic odor. It is completely miscible with water and most organic solvents. Acetone dissolves well many organic substances (cellulose acetate and nitrocellulose, fats, wax, rubber, etc.), as well as a number of salts (calcium chloride, potassium iodide). Is one of the metabolites produced human body.

Application

Raw materials for the synthesis of many important chemical products: acetic anhydride, ketene, diacetone alcohol, mesityl oxide, methyl isobutyl ketone, methyl methacrylate, diphenylpropane, isophorone, biphenol A, etc .;

(CH3) 2CO + 2 C6H5OH → (CH3) 2C (C6H4OH) 2 + H2O

It is widely used in the synthesis of polycarbonates, polyurethanes and epoxy resins.

Laboratory use

In organic chemistry as a polar aprotic solvent, in particular in the alkylation reaction

ArOH + RHal + K2CO3 → ArOR + KHal + KHCO3

for the oxidation of alcohols in the presence of aluminum alkoxides according to Oppenauer

RR`CHOH + CH3C (O) CH3 → RR`C = O + CH3CH (OH) CH3

For the preparation of cooling baths mixed with "dry ice" and liquid nitrogen to a temperature of -78 C.

For washing chemical glassware, due to its low cost, low toxicity, high volatility and easy solubility in water.

For fast drying of dishes and inorganic substances

Phenol (hydroxybenzene, obsolete carbolic acid) C6H5OH - colorless needle crystals that turn pink in air due to oxidation, leading to the formation of colored substances. They have a specific smell of gouache. Let's dissolve in water (6 g per 100 g of water), in alkali solutions, in alcohol, in benzene, in acetone. 5% solution in water is an antiseptic widely used in medicine.

According to data for 2009, the world consumption of phenol has the following structure:

44% of phenol is used for the production of bisphenol A, which, in turn, is used for the production of polycarbonate and epoxy resins;

• 30% of phenol is used for the production of phenol-formaldehyde resins;

• 12% of phenol is converted by hydrogenation into cyclohexanol, which is used to obtain artificial fibers - nylon and nylon;

• the remaining 14% is spent on other needs, including the production of antioxidants (ionol), nonionic surfactants - polyoxyethylated alkyl phenols (neonols), other phenols (cresols), drugs (aspirin), antiseptics (xeroform) and pesticides.

• 1.4% phenol is used in medicine (orasept) as an anesthetic and antiseptic.

Phenol and its derivatives determine the preservative properties of smoke smoke.

Nitrobenzene

Nitrobenzene is a toxic organic substance with an almond odor. Formula C6H5NO2. Appearance - bright yellow crystals or oily liquid, insoluble in water.

Application

It is used as a solvent and mild oxidizing agent. It is mainly used as an intermediate product for the production of aniline.

Raw materials in the production of aniline, aromatic nitrogen-containing compounds (benzidine, quinoline, azobenzene), cellulose ether solvent, a component of polishing compounds for metals.

Aniline (phenylamine) is an organic compound with the formula C6H5NH2, the simplest aromatic amine. It is a colorless oily liquid with a characteristic odor, slightly heavier than water and poorly soluble in it, well soluble in organic solvents. It quickly oxidizes in air and acquires a reddish-brown color. Poisonous.

At the moment, in the world, the main part (85%) of aniline produced is used for the production of methyldiisocyanates (MDI), which are then used for the production of polyurethanes. Aniline is also used in the manufacture of artificial rubbers (9%), herbicides (2%) and dyes (2%).

In Russia, it is mainly used as an intermediate in the production of dyes, explosives and drugs (sulfa drugs), but due to the expected growth in polyurethane production, a significant change in the consumer picture is possible in the medium term.

Medications

Sulfanilic acid HO3S-C6H4- NH2- solid that precipitates from crystallization hot water in the form of shiny scales. The most important derivative of sulfanilic acid is its amide H2N-C6H4-SO2-NH2. It is a colorless crystalline substance, slightly soluble in cold water and good - hot, is the basis of an important class of medicinal substances - sulfa drugs. Their medicinal action was discovered in the early 30s. Since then, more than six thousand compounds of this group have been synthesized. Sulfonamide preparations are widely used in the treatment of various infectious diseases. For example, norsulfazole, sulfadimezin, etazole, streptocid are used to treat respiratory diseases, phthalazole - in the treatment of gastrointestinal infections.

Chlorobenzene

Chlorobenzene (phenyl chloride) is an aromatic organic compound with the formula C6H5Cl, a colorless flammable liquid with a characteristic odor.

Receiving

Chlorobenzene was discovered in 1851 as a product of the reaction of phenol with phosphorus (V) chloride and this is how it is usually obtained in the laboratory. In industry, chlorobenzene is obtained by chlorination of benzene at 80-85 ° C in reactors column type filled with iron rings:

It is isolated by rectification after washing, neutralization and azeotropic drying of the reaction mass.

Application

Chlorobenzene is an important organic solvent, in addition, it is used in organic synthesis, for example, it is used in the synthesis of pesticides (for example, DDT can be obtained by reacting it with chloral (trichloroacetaldehyde)). Also used in the production of phenol:

C6H5Cl + NaOH → C6H5OH + NaCl

Chlorobenzene is also an intermediate product in the production of dichlorobenzenes and some dyes.

Insecticides

Insecticides (from Latin insectum - insect and Latin caedo - I kill) - chemicals for the destruction of harmful insects. Insecticides differ in chemical composition: organochlorine (DDT, hexachloran, etc.), organophosphorus (thiophos, karbofos, methylmercaptophos, dichlorvos, diazinon, etc.), carbamic acid derivatives (methylcarbamate), natural pyrethrins and synthetic arsenites of calcium and sodium, calcium arsenate), sulfur preparations, mineral oils, plant poisons containing alkaloids (anabasine, nicotine, etc.)