Physical properties of ethylene:
Ethylene is a colorless gas with a faint odor, slightly soluble in water, soluble in alcohol, and highly soluble in diethyl ether. When mixed with air it forms an explosive mixture.
Chemical properties of ethylene:
Ethylene is characterized by reactions that proceed through the mechanism of electrophilic addition, radical substitution, oxidation, reduction, and polymerization.

Halogenation(electrophilic addition) - the interaction of ethylene with halogens, for example, with bromine, in which bromine water becomes discolored:

CH2 = CH2 + Br2 = Br-CH2-CH2Br.

Halogenation of ethylene is also possible when heated (300C), in this case the double bond does not break - the reaction proceeds according to the radical substitution mechanism:

CH2 = CH2 + Cl2 → CH2 = CH-Cl + HCl.

Hydrohalogenation - the interaction of ethylene with hydrogen halides (HCl, HBr) with the formation of halogenated alkanes:

CH2 = CH2 + HCl → CH3-CH2-Cl.

Hydration is the interaction of ethylene with water in the presence of mineral acids (sulfuric, phosphoric) with the formation of saturated monohydric alcohol - ethanol:

CH2 = CH2 + H2O → CH3-CH2-OH.

Among the electrophilic addition reactions, addition is distinguished hypochlorous acid(1), hydroxy- and alkoxymercuration reactions (2, 3) (production of organomercury compounds) and hydroboration (4):

CH2 = CH2 + HClO → CH2(OH)-CH2-Cl (1);

CH2 = CH2 + (CH3COO)2Hg + H2O → CH2(OH)-CH2-Hg-OCOCH3 + CH3COOH (2);

CH2 = CH2 + (CH3COO)2Hg + R-OH → R-CH2(OCH3)-CH2-Hg-OCOCH3 + CH3COOH (3);

CH2 = CH2 + BH3 → CH3-CH2-BH2 (4).

Nucleophilic addition reactions are typical for ethylene derivatives containing electron-withdrawing substituents. Among nucleophilic addition reactions, a special place is occupied by the addition reactions of hydrocyanic acid, ammonia, and ethanol. For example,

2ON-CH = CH2 + HCN →2ON-CH2-CH2-CN.

During ethylene oxidation reactions, the formation of various products is possible, and the composition is determined by the oxidation conditions. Thus, during the oxidation of ethylene under mild conditions (the oxidizing agent is potassium permanganate), the π bond is broken and a dihydric alcohol, ethylene glycol, is formed:

3CH2 = CH2 + 2KMnO4 +4H2O = 3CH2(OH)-CH2(OH) +2MnO2 + 2KOH.

During the severe oxidation of ethylene with a boiling solution of potassium permanganate in an acidic environment, complete rupture of the bond (σ-bond) occurs with the formation of formic acid and carbon dioxide:

Oxidation of ethylene with oxygen at 200C in the presence of CuCl2 and PdCl2 leads to the formation of acetaldehyde:

CH2 = CH2 +1/2O2 = CH3-CH = O.

When ethylene is reduced, ethane is formed, a member of the class of alkanes. The reduction reaction (hydrogenation reaction) of ethylene proceeds by a radical mechanism. The condition for the reaction to occur is the presence of catalysts (Ni, Pd, Pt), as well as heating of the reaction mixture:

CH2 = CH2 + H2 = CH3-CH3.

Ethylene undergoes a polymerization reaction. Polymerization is the process of forming a high-molecular compound - a polymer - by combining with each other using the main valences of the molecules of the original low-molecular substance - the monomer. Polymerization of ethylene occurs under the action of acids (cationic mechanism) or radicals (radical mechanism).

Ethylene is the simplest of the organic compounds known as alkenes. It is colorless with a sweetish taste and smell. Natural sources include natural gas and petroleum, and it is also a naturally occurring hormone in plants, in which it inhibits growth and promotes fruit ripening. The use of ethylene is common in industrial organic chemistry. It is produced by heating natural gas, the melting point is 169.4 °C, the boiling point is 103.9 °C.

Ethylene: structural features and properties

Hydrocarbons are molecules containing hydrogen and carbon. They vary greatly in terms of the number of single and double bonds and the structural orientation of each component. One of the simplest, but biologically and economically beneficial hydrocarbons is ethylene. It comes in gaseous form, is colorless and flammable. It consists of two double carbon atoms bonded with hydrogen atoms. The chemical formula is C 2 H 4 . The structural form of the molecule is linear due to the presence of a double bond in the center.
Ethylene has a sweetish, musky odor that makes it easy to identify the substance in the air. This applies to gas in its pure form: the odor may disappear when mixed with other chemicals.

Ethylene application scheme

Ethylene is used in two main categories: as a monomer from which large carbon chains are built, and as a starting material for other two-carbon compounds. Polymerizations are the repeated combinations of many small ethylene molecules into larger ones. This process occurs at high pressures and temperatures. The areas of application of ethylene are numerous. Polyethylene is a polymer that is used particularly extensively in the production of packaging films, wire coverings and plastic bottles. Another use of ethylene as a monomer concerns the formation of linear α-olefins. Ethylene is the starting material for the preparation of a number of two-carbon compounds such as ethanol (industrial alcohol), (antifreeze, and film), acetaldehyde and vinyl chloride. In addition to these compounds, ethylene and benzene form ethylbenzene, which is used in the production of plastics and the substance in question is one of the simplest hydrocarbons. However, the properties of ethylene make it biologically and economically significant.

Commercial use

The properties of ethylene provide a good commercial basis for a large number of organic (carbon and hydrogen containing) materials. Single ethylene molecules can be joined together to make polyethylene (which means many ethylene molecules). Polyethylene is used to make plastics. Additionally, it can be used to make detergents and synthetic lubricants, which are chemicals used to reduce friction. The use of ethylene to produce styrene is important in the process of creating rubber and protective packaging. In addition, it is used in the footwear industry, especially sports shoes, as well as in the production of car tires. The use of ethylene is commercially important, and the gas itself is one of the most commonly produced hydrocarbons globally.

Health Hazard

Ethylene poses a health hazard primarily because it is flammable and explosive. It can also act like a narcotic at low concentrations, causing nausea, dizziness, headaches and loss of coordination. At higher concentrations it acts as an anesthetic, causing loss of consciousness and other irritants. All these negative aspects can be a cause for concern, primarily for people who work directly with gas. The amount of ethylene that most people encounter in everyday life is usually relatively small.

Ethylene reactions

1) Oxidation. This is the addition of oxygen, for example in the oxidation of ethylene to ethylene oxide. It is used in the production of ethylene glycol (1,2-ethanediol), which is used as an antifreeze liquid, and in the production of polyesters by condensation polymerization.

2) Halogenation - reactions with ethylene of fluorine, chlorine, bromine, iodine.

3) Chlorination of ethylene in the form of 1,2-dichloroethane and subsequent conversion of 1,2-dichloroethane into vinyl chloride monomer. 1,2-Dichloroethane is a useful organic solvent and is also a valuable precursor in the synthesis of vinyl chloride.

4) Alkylation - addition of hydrocarbons at a double bond, for example, the synthesis of ethylbenzene from ethylene and benzene, followed by conversion to styrene. Ethylbenzene is an intermediate for the production of styrene, one of the most widely used vinyl monomers. Styrene is a monomer used to produce polystyrene.

5) Combustion of ethylene. The gas is produced by heating and concentrated sulfuric acid.

6) Hydration - a reaction with the addition of water to the double bond. The most important industrial application of this reaction is the conversion of ethylene to ethanol.

Ethylene and combustion

Ethylene is a colorless gas that is poorly soluble in water. The combustion of ethylene in air is accompanied by the formation of carbon dioxide and water. In its pure form, the gas burns with a light diffusion flame. Mixed with a small amount of air, it produces a flame consisting of three separate layers - an inner core of unburned gas, a blue-green layer and an outer cone where the partially oxidized product from the premixed layer is burned in a diffusion flame. The resulting flame shows a complex series of reactions, and if more air is added to the gas mixture, the diffusion layer gradually disappears.

Useful facts

1) Ethylene is a natural plant hormone, it affects the growth, development, maturation and aging of all plants.

2) The gas is not harmful or toxic to humans in a certain concentration (100-150 mg).

3) It is used in medicine as an anesthetic.

4) The action of ethylene slows down at low temperatures.

5) A characteristic property is good penetration through most substances, for example through cardboard packaging boxes, wooden and even concrete walls.

6) While it is invaluable for its ability to initiate the ripening process, it can also be very harmful to many fruits, vegetables, flowers and plants, accelerating the aging process and reducing product quality and shelf life. The extent of damage depends on the concentration, duration of exposure and temperature.

7) Ethylene is explosive at high concentrations.

8) Ethylene is used in the production of specialty glass for the automotive industry.

9) Metal fabrication: The gas is used as oxyfuel gas for metal cutting, welding and high speed thermal spraying.

10) Petroleum refining: Ethylene is used as a refrigerant, especially in natural gas liquefaction industries.

11) As mentioned earlier, ethylene is a very reactive substance, in addition, it is also very flammable. For safety reasons, it is usually transported through a special separate gas pipeline.

12) One of the most common products made directly from ethylene is plastic.

Among vegetable growers who are engaged in the cultivation and supply of agricultural crops professionally, it is customary to collect fruits that have not passed the ripening stage. This approach allows you to preserve vegetables and fruits longer and transport them over long distances without problems. Since green bananas or, for example, tomatoes are unlikely to be in serious demand among the average consumer, and natural ripening can take a long time, gases are used to speed up the process ethylene And acetylene. At first glance, this approach may cause bewilderment, but delving into the physiology of the process, it becomes clear why modern vegetable growers actively use such technology.

Gas ripening hormone for vegetables and fruits

The influence of specific gases on the rate of ripening of crops was first noticed by the Russian botanist Dmitry Nelyubov, who at the beginning of the 20th century. determined a certain dependence of the “ripeness” of lemons on the atmosphere in the room. It turned out that in warehouses with an old heating system, which was not highly airtight and allowed steam to escape into the atmosphere, lemons ripened much faster. Through a simple analysis, it was found that this effect was achieved thanks to ethylene and acetylene, which were contained in the steam emanating from the pipes.

At first, such a discovery was deprived of due attention from entrepreneurs; only rare innovators tried to saturate their storage facilities with ethylene gas to improve productivity. Only in the middle of the 20th century. The “gas hormone” for vegetables and fruits has been adopted by fairly large enterprises.

To implement the technology, cylinders are usually used, the valve system of which allows you to accurately adjust the gas output and achieve the required concentration in the room. It is very important that in this case ordinary air, which contains oxygen, the main oxidizing agent for agricultural products, is displaced from the storage facility. By the way, the technology of replacing oxygen with another substance is actively used to increase the shelf life of not only fruits, but also other food products - meat, fish, cheeses, etc. Nitrogen and carbon dioxide are used for this purpose, as discussed in detail.

Why is ethylene gas called "banana" gas?

So, the ethylene environment allows you to speed up the ripening process of vegetables and fruits. But why is this happening? The fact is that during the ripening process, many crops release a special substance, which is ethylene, which, when released into the environment, affects not only the source of the release itself, but also its neighbors.

this is how apples help with ripening

Each type of fruit produces different amounts of ripening hormone. The biggest differences in this regard are:

• apples;
• pears;
• apricots;
• bananas.

The latter enter our country over a considerable distance, so they are not transported in ripe form. In order for banana peels to acquire their natural bright yellow color, many entrepreneurs place them in a special chamber that is filled with ethylene. The cycle of such treatment is on average 24 hours, after which bananas receive a kind of impetus to accelerated ripening. It is interesting that without such a procedure, the favorite fruit of many children and adults will remain in a semi-ripe state for a very long time. Therefore, “banana” gas is simply necessary in this case.

sent for ripening

Methods for creating the required gas concentration in the fruit storage chamber

It was already noted above that to ensure the required concentration of ethylene/acetylene in the storage room for vegetables and fruits, gas cylinders are usually used. In order to save money, some vegetable growers sometimes resort to another method. In the room with the fruits, a piece of calcium carbide is placed, onto which water drips at intervals of 2-3 drops/hour. As a result of the chemical reaction, acetylene is released, gradually filling the internal atmosphere.

This “old-fashioned” method, although attractive in its simplicity, is more typical for private households, since it does not allow achieving the exact concentration of gas in the room. Therefore, in medium and large enterprises, where it is important to calculate the required amount of “gas hormone” for each crop, balloon installations are often used.

The correct formation of the gas environment during the storage and production of food products plays a huge role, making it possible to improve the appearance of the product, its taste and increase its shelf life. Read more about methods of packaging and storing products in a series of articles about food gas mixtures, and you can order these products by selecting the required gas and, if desired, receiving advice on its proper use.

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Find

Meaning of the word ethylene

ethylene in the crossword dictionary

Explanatory dictionary of the Russian language. D.N. Ushakov

Explanatory dictionary of the Russian language. S.I.Ozhegov, N.Yu.Shvedova.

ethylene

A, m. Colorless gas is one of the main products of the petrochemical industry.

adj. ethylene, -aya, -oh.

New explanatory dictionary of the Russian language, T. F. Efremova.

ethylene

m. Colorless flammable gas, one of the main products of the petrochemical industry.

Encyclopedic Dictionary, 1998

ethylene

H2C=CH2, colorless gas, boiling point -103.7°C. Contains in large quantities (up to 20%) in oil refining gases; is part of coke oven gas. One of the main products of the petrochemical industry: used for the synthesis of vinyl chloride, ethylene oxide, ethyl alcohol, polyethylene, etc.

Ethylene

ethene, H2C=CH2, unsaturated hydrocarbon, the first member of the homologous series of olefins, colorless gas with a faint ethereal odor; tnл ≈ 169.5╟С, tkip ≈ 103.8╟С, density 0.570 g/cm3 (at tkip); practically insoluble in water, poorly ≈ in alcohol, better ≈ in ether, acetone. Ignition temperature 540╟С, burns with a low-smoking flame, forms explosive mixtures with air (3
--34 volume %). E. is very reactive. Its most typical addition is through a carbon-carbon double bond; for example, catalytic hydrogenation of ethane leads to ethane:

H2C = CH2 + H2 ╝ H3C≈CH3,

chlorination ≈ to dichloroethane:

H2C = CH2 + Cl2 ╝ ClH2C≈CH2Cl,

hypochlorination (addition of hypochlorous acid) ≈ to ethylene chlorohydrin:

H2C=CH2 + HOCl ╝ HOH2C≈CH2Cl.

Many E. reactions underlie industrial methods for producing a number of important products; Thus, ethyl alcohol is obtained by sulfuric acid or direct hydration from E., by catalytic oxidation ≈ ethylene oxide and acetaldehyde, by alkylation of benzene (according to the Friedel ≈ Crafts reaction) ≈ ethylbenzene, by polymerization, for example in the presence of Ziegler catalysts ≈ Natta, ≈ polyethylene, by oxidative chlorination ≈ vinyl chloride , combination with acetic acid ≈ vinyl acetate, addition of HCl ≈ ethyl chloride, interaction with sulfur chlorides ≈ mustard gas, etc. The main industrial methods for producing ethylene are high-temperature (700≈850╟C) pyrolysis and cracking of liquid petroleum distillates and lower paraffin hydrocarbons, mainly ethane and propane (see Refinery gases). Isolation and purification of E. is carried out by rectification, fractional absorption, and deep cooling. In laboratory conditions, E. can be obtained by dehydration of ethyl alcohol, for example, by heating with sulfuric or phosphoric acid.

Ethylene in the body. E. is formed in small quantities in the tissues of plants and animals as an intermediate product of metabolism. Contained in various organs of higher plants (fruits, flowers, leaves, stems, roots), E. antagonistically interacts with plant hormones ≈ auxins (E. and auxins inhibit the biosynthesis and functioning of each other). A shift towards the predominant action of E. contributes to a slowdown in growth, accelerated aging, ripening and falling of fruits, accelerated shedding of flowers or only their corollas, ovaries, leaves, and in the direction of the predominant action of auxins, it slows down the aging, ripening and falling of fruits, etc. The pathways of E. biosynthesis and its metabolism in plant tissues have not been fully elucidated.

E. is used to accelerate the ripening of fruits (for example, tomatoes, melons, oranges, tangerines, lemons, bananas), defoliate plants, reduce pre-harvest fruit abscission, and to reduce the strength of fruit attachment to mother plants, which facilitates mechanized harvesting. In high concentrations, E. has a narcotic effect on humans and animals.

Lit.: Jensen Yu., Ethylene and polyacetylenes, in the book: Plant Biochemistry, trans. from English, M., 1968; Stimulation and inhibition of physiological processes in plants, in the collection: History and current state of plant physiology, M., 1967.

Yu. V. Rakitin.

Wikipedia

Ethylene

Ethylene(according to IUPAC: ethene) is an organic chemical compound described by the formula CH. It is the simplest alkene ( olefin), an isologist of ethane. Under normal conditions, it is a colorless flammable gas with a density of 1.178 kg/m³ and a slight odor. Partially soluble in water (25.6 ml in 100 ml of water at 0 °C), ethanol (359 ml in the same conditions). It is highly soluble in diethyl ether and hydrocarbons.
Contains a double bond and therefore belongs to unsaturated or unsaturated hydrocarbons. It plays an extremely important role in industry and is also a phytohormone. Ethylene is the most produced organic compound in the world; Total global ethylene production in 2008 was 113 million tons and continues to grow by 2-3% per year. Ethylene has a narcotic effect. Hazard class - fourth.

Examples of the use of the word ethylene in literature.

Including many new ones: oxide ethylene, butane, butylene, butadiene, isopropylene, vinyl acetate, methylstyrene, quinoline and cresol.

An engine running on gasoline emits relatively easily oxidized substances - ethyl and ethylene, and the gas engine is methane, which of all saturated hydrocarbons is the most resistant to oxidation.

To the right of the course - lake, liquid ethylene, - Tellur spoke into the microphone in an even voice.

Physical properties

Ethan under n. y is a colorless, odorless gas. Molar mass - 30.07. Melting point -182.81 °C, boiling point -88.63 °C. . Density ρ gas. =0.001342 g/cm³ or 1.342 kg/m³ (no.), ρ liquid. =0.561 g/cm³ (T=-100 °C). Dissociation constant 42 (in water, standard) [ source?] . Vapor pressure at 0 °C - 2.379 MPa.

Chemical properties

Chemical formula C 2 H 6 (rational CH 3 CH 3). The most typical reactions are the replacement of hydrogen with halogens, which occur via a free radical mechanism. Thermal dehydrogenation of ethane at 550-650 °C leads to ketene, at temperatures above 800 °C - cacetylene (benzolysate is also formed). Direct chlorination at 300-450 °C - ethyl chloride, nitration in the gas phase gives a mixture (3:1) of nitroethane and tromethane.

Receipt

In industry

In industry it is obtained from petroleum and natural gases, where it accounts for up to 10% by volume. In Russia, the ethane content in oil gases is very low. In the USA and Canada (where its content in oil and natural gases is high) it serves as the main raw material for the production of ethene.

In laboratory conditions

Obtained from iodomethane by the Wurtz reaction, from sodium acetate by electrolysis by the Kolbe reaction, by fusion of sodium propionate with alkali, from ethyl bromide by the Grignard reaction, by hydrogenation of ethene (over Pd) or acetylene (in the presence of Raney Nickel).

Application

The main use of ethane in industry is the production of ethylene.

Butane(C 4 H 10) - organic compound of the class alkanes. In chemistry, the name is used primarily to refer to n-butane. The mixture of n-butane and its isomer isobutane CH(CH 3) 3 . The name comes from the root "but-" (English name butyric acid - butyric acid) and the suffix “-an” (belonging to alkanes). In high concentrations it is poisonous; inhalation of butane causes dysfunction of the pulmonary-respiratory system. Contained in natural gas, is formed when cracking petroleum products, when dividing the passing oil gas, "fat" natural gas. As a representative of hydrocarbon gases, it is fire and explosive, low-toxic, has a specific characteristic odor, and has narcotic properties. In terms of the degree of impact on the body, the gas belongs to substances of the 4th hazard class (low-hazard) according to GOST 12.1.007-76. Harmful effects on the nervous system .

Isomerism

Butane has two isomer:

Physical properties

Butane is a colorless flammable gas, with a specific odor, easily liquefied (below 0 °C and normal pressure or at elevated pressure and normal temperature - a highly volatile liquid). Freezing point -138°C (at normal pressure). Solubility in water - 6.1 mg in 100 ml of water (for n-butane, at 20 °C, much better soluble in organic solvents ). Can form azeotropic mixture with water at a temperature of about 100 °C and a pressure of 10 atm.

Finding and receiving

Contained in gas condensate and petroleum gas (up to 12%). It is a product of catalytic and hydrocatalytic cracking oil fractions. Can be obtained in the laboratory by Wurtz reactions.

2 C 2 H 5 Br + 2Na → CH 3 -CH 2 -CH 2 -CH 3 + 2NaBr

Desulphurization (demercaptanization) of butane fraction

The straight-run butane fraction must be purified from sulfur compounds, which are mainly represented by methyl and ethyl mercaptans. The method for purifying the butane fraction from mercaptans consists of alkaline extraction of mercaptans from the hydrocarbon fraction and subsequent regeneration of the alkali in the presence of homogeneous or heterogeneous catalysts with atmospheric oxygen with the release of disulfide oil.

Applications and reactions

During free radical chlorination it forms a mixture of 1-chloro- and 2-chlorobutane. Their ratio is well explained by the difference in the strength of C-H bonds in positions 1 and 2 (425 and 411 kJ/mol). Upon complete combustion in air it forms carbon dioxide and water. Butane is used in a mixture with propane in lighters, in gas cylinders in a liquefied state, where it has an odor, as it contains specially added odorants. In this case, “winter” and “summer” mixtures with different compositions are used. Heat of combustion 1 kg - 45.7 MJ (12.72 kWh).

2C 4 H 10 + 13 O 2 → 8 CO 2 + 10 H 2 O

When there is a lack of oxygen, it forms soot or carbon monoxide or both together.

2C 4 H 10 + 5 O 2 → 8 C + 10 H 2 O

2C 4 H 10 + 9 O 2 → 8 CO + 10 H 2 O

By company DuPont a method has been developed for obtaining maleic anhydride from n-butane by catalytic oxidation.

2 CH 3 CH 2 CH 2 CH 3 + 7 O 2 → 2 C 2 H 2 (CO) 2 O + 8 H 2 O

n-Butane - raw material for production butene, 1,3-butadiene, a component of high octane gasolines. High purity butane and especially isobutane can be used as a refrigerant in refrigeration units. The performance of such systems is slightly lower than that of freon systems. Butane is environmentally friendly, unlike freon refrigerants.

In the food industry, butane is registered as food additives E943a, and isobutane - E943b, How propellant, for example, in deodorants.

Ethylene(By IUPAC: ethene) - organic chemical compound, described by the formula C 2 H 4. Is the simplest alkene (olefin). Ethylene practically does not occur in nature. It is a colorless, flammable gas with a faint odor. Partially soluble in water (25.6 ml in 100 ml of water at 0°C), ethanol (359 ml in the same conditions). It is highly soluble in diethyl ether and hydrocarbons. Contains a double bond and is therefore classified as unsaturated or unsaturated hydrocarbons. Plays an extremely important role in industry and is also phytohormone. Ethylene is the most produced organic compound in the world ; total world ethylene production in 2008 amounted to 113 million tons and continues to grow by 2-3% per year .

Application

Ethylene is the leading product basic organic synthesis and is used to produce the following compounds (listed in alphabetical order):

Vinyl acetate;

Dichloroethane / vinyl chloride(3rd place, 12% of the total volume);

Ethylene oxide(2nd place, 14-15% of the total volume);

Polyethylene(1st place, up to 60% of the total volume);

Styrene;

Acetic acid;

Ethylbenzene;

Ethylene glycol;

Ethanol.

Ethylene mixed with oxygen has been used in medicine for anesthesia until the mid-80s of the twentieth century in the USSR and the Middle East. Ethylene is phytohormone in almost all plants , among other things is responsible for the fall of needles in conifers.

Basic chemical properties

Ethylene is a chemically active substance. Since there is a double bond between the carbon atoms in the molecule, one of them, which is less strong, is easily broken, and at the site of the bond break the attachment, oxidation, and polymerization of molecules occurs.

Halogenation:

CH 2 =CH 2 + Cl 2 → CH 2 Cl-CH 2 Cl

Bromine water becomes discolored. This is a qualitative reaction to unsaturated compounds.

Hydrogenation:

CH 2 =CH 2 + H - H → CH 3 - CH 3 (under the influence of Ni)

Hydrohalogenation:

CH 2 =CH 2 + HBr → CH 3 - CH 2 Br

Hydration:

CH 2 =CH 2 + HOH → CH 3 CH 2 OH (under the influence of a catalyst)

This reaction was discovered by A.M. Butlerov, and it is used for the industrial production of ethyl alcohol.

Oxidation:

Ethylene oxidizes easily. If ethylene is passed through a solution of potassium permanganate, it will become discolored. This reaction is used to distinguish between saturated and unsaturated compounds.

Ethylene oxide is a fragile substance; the oxygen bridge breaks and water joins, resulting in the formation ethylene glycol:

C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

Polymerization:

nCH 2 =CH 2 → (-CH 2 -CH 2 -) n

Isoprene CH 2 =C(CH3)-CH=CH2, 2-methylbutadiene-1,3 - unsaturated hydrocarbon diene series (C n H 2n−2 ) . Under normal conditions, colorless liquid. He is monomer For natural rubber and a structural unit for many molecules of other natural compounds - isoprenoids, or terpenoids. . Soluble in alcohol. Isoprene polymerizes to give isoprene rubbers. Isoprene also reacts polymerization with vinyl compounds.

Finding and receiving

Natural rubber is a polymer of isoprene - most commonly cis-1,4-polyisoprene with a molecular weight of 100,000 to 1,000,000. Contains several percent of other materials as impurities, such as squirrels, fatty acid, resins and inorganic substances. Some sources of natural rubber are called gutta-percha and consists of trans-1,4-polyisoprene, structural isomer, which has similar but not identical properties. Isoprene is produced and released into the atmosphere by many types of trees (the main one is oak) Annual production of isoprene by vegetation is about 600 million tons, with half produced by tropical broadleaf trees, the rest produced by shrubs. Once released into the atmosphere, isoprene is converted by free radicals (such as hydroxyl (OH) radicals) and, to a lesser extent, by ozone into various substances such as aldehydes, hydroxyperoxides, organic nitrates and epoxides, which mix with water droplets to form aerosols or haze. Trees use this mechanism not only to avoid overheating of the leaves by the Sun, but also to protect against free radicals, especially ozone. Isoprene was first obtained by heat treatment of natural rubber. Most industrially available as a thermal product cracking naphtha or oils, and also as a by-product in the production ethylene. Produced around 20,000 tons per year. About 95% of isoprene production is used to make cis-1,4-polyisoprene, a synthetic version of natural rubber.

Butadiene-1.3(divinyl) CH 2 =CH-CH=CH2 - unsaturated hydrocarbon, the simplest representative diene hydrocarbons.

Physical properties

Butadiene - colorless gas with a characteristic odor, boiling temperature−4.5 °C, melting temperature−108.9 °C, flash point−40 °C, maximum permissible concentration in air (maximum permissible concentration) 0.1 g/m³, density 0.650 g/cm³ at −6 °C.

Slightly soluble in water, highly soluble in alcohol, kerosene with air in an amount of 1.6-10.8%.

Chemical properties

Butadiene is prone to polymerization, easily oxidizes air with education peroxide compounds that accelerate polymerization.

Receipt

Butadiene is produced by the reaction Lebedeva transmission ethyl alcohol through catalyst:

2CH 3 CH 2 OH → C 4 H 6 + 2H 2 O + H 2

Or dehydrogenation of normal butylene:

CH 2 =CH-CH 2 -CH 3 → CH 2 =CH-CH=CH 2 + H 2

Application

The polymerization of butadiene produces synthetic rubber. Copolymerization with acrylonitrile And styrene get ABS plastic.

Benzene (C 6 H 6 , Ph H) - organic chemical compound, colorless liquid with a pleasant sweetish smell. simplest aromatic hydrocarbon. Benzene is included in gasoline, widely used in industry, is the raw material for production medications, various plastics, synthetic rubber, dyes. Although benzene is included crude oil, on an industrial scale it is synthesized from its other components. Toxic, carcinogenic.

Physical properties

Colorless liquid with a peculiar pungent odor. Melting point = 5.5 °C, boiling point = 80.1 °C, density = 0.879 g/cm³, molar mass = 78.11 g/mol. Like all hydrocarbons, benzene burns and produces a lot of soot. Forms explosive mixtures with air, mixes well with ethers, gasoline and other organic solvents, forms an azeotropic mixture with water with a boiling point of 69.25 °C (91% benzene). Solubility in water 1.79 g/l (at 25 °C).

Chemical properties

Benzene is characterized by substitution reactions - benzene reacts with alkenes, chlorine alkanes, halogens, nitrogen And sulfuric acids. Reactions of cleavage of the benzene ring take place under harsh conditions (temperature, pressure).

Interaction with chlorine in the presence of a catalyst:

From 6 H 6 + Cl 2 -(FeCl 3) → From 6 H 5 Cl + HCl chlorobenzene is formed

Catalysts promote the creation of an active electrophilic species by polarization between halogen atoms.

Cl-Cl + FeCl 3 → Cl ઠ - ઠ +

C 6 H 6 + Cl ઠ - -Cl ઠ + + FeCl 3 → [C 6 H 5 Cl + FeCl 4 ] → C 6 H 5 Cl + FeCl 3 + HCl

In the absence of a catalyst, a radical substitution reaction occurs when heated or illuminated.

With 6 H 6 + 3Cl 2 - (lighting) → C 6 H 6 Cl 6 a mixture of hexachlorocyclohexane isomers is formed video

Reaction with bromine (pure):

Interaction with halogen derivatives of alkanes ( Friedel-Crafts reaction):

C 6 H 6 + C 2 H 5 Cl -(AlCl 3) → C 6 H 5 C 2 H 5 + HCl ethylbenzene is formed

C 6 H 6 + HNO 3 -(H 2 SO 4) → C 6 H 5 NO 2 + H 2 O

Structure

Benzene is unsaturated in composition. hydrocarbons(homologous series C n H 2n-6), but unlike hydrocarbons of the series ethylene C 2 H 4 exhibits properties inherent to unsaturated hydrocarbons (they are characterized by addition reactions) only under harsh conditions, but benzene is more prone to substitution reactions. This “behavior” of benzene is explained by its special structure: the location of all bonds and molecules on the same plane and the presence of a conjugated 6π-electron cloud in the structure. The modern understanding of the electronic nature of bonds in benzene is based on the hypothesis Linus Pauling, who proposed to depict the benzene molecule as a hexagon with an inscribed circle, thereby emphasizing the absence of fixed double bonds and the presence of a single electron cloud covering all six carbon atoms of the cycle.

Production

Today, there are three fundamentally different methods for producing benzene.

Coking coal. This process was historically the first and served as the main source of benzene until World War II. Currently, the share of benzene produced by this method is less than 1%. It should be added that benzene obtained from coal tar contains a significant amount of thiophene, which makes such benzene a raw material unsuitable for a number of technological processes.

Catalytic reforming(aromaizing) gasoline fractions of oil. This process is the main source of benzene in the United States. In Western Europe, Russia and Japan, 40-60% of the total amount of the substance is obtained using this method. In this process, in addition to benzene, toluene And xylenes. Due to the fact that toluene is produced in quantities exceeding the demand for it, it is also partially processed into:

benzene - by hydrodealkylation method;

a mixture of benzene and xylenes - by disproportionation method;

Pyrolysis gasoline and heavier petroleum fractions. Up to 50% of benzene is produced by this method. Along with benzene, toluene and xylenes are formed. In some cases, this entire fraction is sent to the dealkylation stage, where both toluene and xylenes are converted to benzene.

Application

Benzene is one of the ten most important substances in the chemical industry. [ source not specified 232 days ] Most of the benzene produced is used for the synthesis of other products:

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

  about 25% of benzene is converted into cumene (alkylation benzene propylene);

  approximately 10-15% benzene hydrogenate V cyclohexane;

  about 10% of benzene is spent on production nitrobenzene;

  2-3% benzene is converted into linear alkylbenzenes;

  approximately 1% benzene is used for synthesis chlorobenzene.

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

Toluene(from Spanish Tolu, Tolu balsam) - methylbenzene, a colorless liquid with a characteristic odor, belongs to the arenes.

Toluene was first obtained by P. Peltier in 1835 during the distillation of pine resin. In 1838, A. Deville isolated it from a balsam brought from the city of Tolu in Colombia, after which it received its name.

general characteristics

A colorless, mobile, volatile liquid with a pungent odor, exhibits a weak narcotic effect. Miscible within unlimited limits with hydrocarbons, many alcohols And ethers, does not mix with water. Refractive index light 1.4969 at 20 °C. It is flammable and burns with a smoky flame.

Chemical properties

Toluene is characterized by electrophilic substitution reactions in the aromatic ring and substitution in the methyl group according to the radical mechanism.

Electrophilic substitution in the aromatic ring it occurs predominantly in the ortho- and para-positions relative to the methyl group.

In addition to substitution reactions, toluene undergoes addition reactions (hydrogenation) and ozonolysis. Some oxidizing agents (alkaline solution of potassium permanganate, dilute nitric acid) oxidize the methyl group to a carboxyl group. Self-ignition temperature 535 °C. Concentration limit of flame propagation, %vol. Temperature limit of flame propagation, °C. Flash point 4 °C.

Interaction with potassium permanganate in an acidic environment:

5C 6 H 5 CH 3 + 6KMnO 4 + 9H 2 SO 4 → 5C 6 H 5 COOH + 6MnSO 4 + 3K 2 SO 4 + 14H 2 O formation of benzoic acid

Preparation and purification

Product catalytic reforming gasoline factions oil. Isolated by selective extraction and subsequent rectification.Also good yields are achieved with catalytic dehydrogenation heptane through methylcyclohexane. Toluene is purified in the same way benzene, only if used concentrated sulfuric acid We must not forget that toluene sulfonated lighter than benzene, which means it is necessary to maintain a lower temperature reaction mixture(less than 30 °C). Toluene also forms an azeotrope with water .

Toluene can be obtained from benzene by Friedel-Crafts reactions:

Application

Raw materials for production benzene, benzoic acid, nitrotoluenes(including trinitrotoluene), toluene diisocyanates(via dinitrotoluene and toluene diamine) benzyl chloride and other organic substances.

Is solvent for many polymers, is part of various commercial solvents for varnishes And paints. Included in solvents: R-40, R-4, 645, 646 , 647 , 648. Used as a solvent in chemical synthesis.

Naphthalene- C 10 H 8 solid crystalline substance with characteristic smell. It does not dissolve in water, but it does well in benzene, on air, alcohol, chloroform.

Chemical properties

Naphthalene is similar in chemical properties to benzene: easily nitrates, sulfonated, interacts with halogens. It differs from benzene in that it reacts even more easily.

Physical properties

Density 1.14 g/cm³, melting point 80.26 °C, boiling point 218 °C, solubility in water approximately 30 mg/l, flash point 79 - 87 °C, auto-ignition temperature 525 °C, molar mass 128.17052 g/mol.

Receipt

Naphthalene is obtained from coal tar. Naphthalene can also be isolated from heavy pyrolysis resin (quenching oil), which is used in the pyrolysis process in ethylene plants.

Termites also produce naphthalene. Coptotermes formosanus to protect their nests from ants, fungi and nematodes .

Application

Important raw material of the chemical industry: used for synthesis phthalic anhydride, tetralin, decalin, various naphthalene derivatives.

Naphthalene derivatives are used to produce dyes And explosives, V medicine, How insecticide.