Or ethene(IUPAC) - C 2 H 4, the simplest and most important representative of a number of unsaturated hydrocarbons with one double bond.

Since 1979, IUPAC rules have recommended that the name "ethylene" be used only for the divalent hydrocarbon substituent CH 2 CH 2 -, and the unsaturated hydrocarbon CH 2 \u003d CH 2 be called "ethene".

Physical Properties

Ethylene is a colorless gas with a slight pleasant odour. It is slightly lighter than air. Slightly soluble in water, but in alcohol and other organic solvents dissolves well.

Structure

Molecular formula C 2 H 4. Structural and electronic formula:

Structural formula of ethylene

Electronic formula of ethylene

Chemical properties

Unlike methane, ethylene is chemically quite active. It is characterized by addition reactions at the site of a double bond, polymerization reactions and oxidation reactions. In this case, one of the double bonds is broken and a simple single bond remains in its place, and due to the released valences, other atoms or atomic groups are attached. Let's look at some examples of reactions. When ethylene is passed into bromine water (an aqueous solution of bromine), the latter becomes colorless due to the interaction of ethylene with bromine to form dibromoethane (ethylene bromide) C 2 H 4 Br 2:

As can be seen from the scheme of this reaction, it is not the replacement of hydrogen atoms by halogen atoms, as in saturated hydrocarbons, but the addition of bromine atoms at the site of the double bond. Ethylene also discolors easily purple aqueous solution potassium permanganate KMnO 4 even at normal temperature. At the same time, ethylene itself is oxidized to ethylene glycol C 2 H 4 (OH) 2. This process can be represented by the following equations:

Reactions between ethylene and bromine and potassium permanganate serve to discover unsaturated hydrocarbons. Methane and other saturated hydrocarbons, as already noted, do not interact with potassium permanganate.

Ethylene reacts with hydrogen. So, when a mixture of ethylene and hydrogen is heated in the presence of a catalyst (nickel, platinum or palladium powder), they combine to form ethane:

Reactions in which hydrogen is added to a substance are called hydrogenation or hydrogenation reactions. Hydrogenation reactions are of great practical importance. they are quite often used in industry. Unlike methane, ethylene burns in air with a swirling flame, since it contains more carbon than methane. Therefore, not all carbon burns out immediately and its particles become very hot and glow. These carbon particles then burn in the outer part of the flame:

Ethylene, like methane, forms explosive mixtures with air.

Receipt

Ethylene does not occur naturally, except for minor impurities in natural gas. Under laboratory conditions, ethylene is usually produced by the action of concentrated sulfuric acid on ethanol when heated. This process can be represented by the following summary equation:

During the reaction, water elements are subtracted from the alcohol molecule, and the released two valences saturate each other with the formation of a double bond between carbon atoms. For industrial purposes, ethylene is produced in large quantities from petroleum cracking gases.

Application

In modern industry, ethylene is widely used for the synthesis of ethyl alcohol and the production of important polymer materials(polyethylene, etc.), as well as for the synthesis of other organic matter. A very interesting property of ethylene is to accelerate the ripening of many garden and garden fruits (tomatoes, melons, pears, lemons, etc.). Using this, the fruits can be transported while still green, and then brought to a ripe state already at the place of consumption, introducing into the air storage facilities small amounts of ethylene.

The history of the discovery of ethylene

Ethylene was first obtained by the German chemist Johann Becher in 1680 by the action of vitriol oil (H 2 SO 4) on wine (ethyl) alcohol (C 2 H 5 OH).

CH 3 -CH 2 -OH + H 2 SO 4 → CH 2 \u003d CH 2 + H 2 O

Initially, it was identified with "combustible air", i.e., with hydrogen. Later, in 1795, the Dutch chemists Deiman, Pots-van-Trusvik, Bond and Lauerenburg similarly obtained ethylene and described it under the name "oxygen gas", as they discovered the ability of ethylene to attach chlorine to form an oily liquid - ethylene chloride ("oil of Dutch chemists"), (Prokhorov, 1978).

The study of the properties of ethylene, its derivatives and homologues began in the middle of the 19th century. The beginning of the practical use of these compounds was laid by the classical studies of A.M. Butlerov and his students in the field of unsaturated compounds and especially the creation of Butlerov's theory chemical structure. In 1860, he obtained ethylene by the action of copper on methylene iodide, establishing the structure of ethylene.

In 1901, Dmitry Nikolaevich Nelyubov grew peas in a laboratory in St. Petersburg, but the seeds produced twisted, shortened seedlings, in which the top was bent with a hook and did not bend. In the greenhouse and fresh air the seedlings were even, tall, and the top quickly straightened the hook in the light. Nelyubov suggested that the factor causing the physiological effect is in the laboratory air.

At that time, the premises were lit with gas. The same gas burned in the street lamps, and it has long been noticed that in the event of an accident in a gas pipeline, trees standing near the site of a gas leak turn yellow prematurely and shed their leaves.

The lighting gas contained a variety of organic substances. To remove the admixture of gas, Nelyubov passed it through a heated tube with copper oxide. Pea seedlings developed normally in "purified" air. In order to find out exactly which substance causes the response of seedlings, Nelyubov added various components of the lighting gas in turn, and found that the addition of ethylene causes:

1) slow growth in length and thickening of the seedling,

2) "non-bending" apical loop,

3) Changing the orientation of the seedling in space.

This physiological reaction of seedlings has been called the triple response to ethylene. Peas were so sensitive to ethylene that they began to use them in bioassays to detect low concentrations of this gas. It was soon discovered that ethylene also causes other effects: leaf fall, fruit ripening, etc. It turned out that plants themselves are capable of synthesizing ethylene; ethylene is a phytohormone (Petushkova, 1986).

Physical properties of ethylene

Ethylene- an organic chemical compound described by the formula C 2 H 4 . It is the simplest alkene ( olefin).

Ethylene is a colorless gas with a faint sweet odor, with a density of 1.178 kg/m³ (lighter than air), and its inhalation has a narcotic effect on humans. Ethylene is soluble in ether and acetone, much less in water and alcohol. Forms an explosive mixture when mixed with air

Solidifies at -169.5°C, melts at the same temperature conditions. Ethene boils at –103.8°C. Ignites when heated to 540°C. The gas burns well, the flame is luminous, with a weak soot. rounded molar mass substances - 28 g / mol. The third and fourth representatives of the ethene homologous series are also gaseous substances. The physical properties of the fifth and following alkenes are different, they are liquids and solids.

Ethylene production

The main methods for producing ethylene:

Dehydrohalogenation of halogen derivatives of alkanes under the action of alcoholic solutions of alkalis

CH 3 -CH 2 -Br + KOH → CH 2 = CH 2 + KBr + H 2 O;

Dehalogenation of dihalogenated alkanes under the action of active metals

Cl-CH 2 -CH 2 -Cl + Zn → ZnCl 2 + CH 2 = CH 2;

Ethylene dehydration when it is heated with sulfuric acid (t>150˚ C) or when its vapor is passed over a catalyst

CH 3 -CH 2 -OH → CH 2 = CH 2 + H 2 O;

Dehydrogenation of ethane on heating (500C) in the presence of a catalyst (Ni, Pt, Pd)

CH 3 -CH 3 → CH 2 \u003d CH 2 + H 2.

Chemical properties of ethylene

Ethylene is characterized by reactions proceeding by the mechanism of electrophilic, addition, radical substitution reactions, oxidation, reduction, and polymerization.

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

CH 2 \u003d CH 2 + Br 2 \u003d Br-CH 2 -CH 2 Br.

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

CH 2 \u003d CH 2 + Cl 2 → CH 2 \u003d CH-Cl + HCl.

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

CH 2 \u003d CH 2 + HCl → CH 3 -CH 2 -Cl.

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

CH 2 \u003d CH 2 + H 2 O → CH 3 -CH 2 -OH.

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

CH 2 \u003d CH 2 + HClO → CH 2 (OH) -CH 2 -Cl (1);

CH 2 \u003d CH 2 + (CH 3 COO) 2 Hg + H 2 O → CH 2 (OH) -CH 2 -Hg-OCOCH 3 + CH 3 COOH (2);

CH 2 = CH 2 + (CH 3 COO) 2 Hg + R-OH → R-CH 2 (OCH 3) -CH 2 -Hg-OCOCH 3 + CH 3 COOH (3);

CH 2 \u003d CH 2 + BH 3 → CH 3 -CH 2 -BH 2 (4).

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

2 ON-CH \u003d CH 2 + HCN → 2 ON-CH 2 -CH 2 -CN.

4. oxidation. Ethylene is easily oxidized. If ethylene is passed through a solution of potassium permanganate, it will become colorless. This reaction is used to distinguish between saturated and unsaturated compounds. The result is ethylene glycol.

3CH 2 \u003d CH 2 + 2KMnO 4 + 4H 2 O \u003d 3CH 2 (OH) -CH 2 (OH) + 2MnO 2 + 2KOH.

At hard oxidation ethylene with a boiling solution of potassium permanganate in acidic environment there is a complete rupture of the bond (σ-bond) with the formation of formic acid and carbon dioxide:

Oxidation ethylene oxygen at 200C in the presence of CuCl 2 and PdCl 2 leads to the formation of acetaldehyde:

CH 2 \u003d CH 2 + 1 / 2O 2 \u003d CH 3 -CH \u003d O.

5. hydrogenation. At recovery ethylene is the formation of ethane, a representative of the class of alkanes. The reduction reaction (hydrogenation reaction) of ethylene proceeds by a radical mechanism. The condition for the reaction to proceed is the presence of catalysts (Ni, Pd, Pt), as well as heating the reaction mixture:

CH 2 \u003d CH 2 + H 2 \u003d CH 3 -CH 3.

6. Ethylene enters into polymerization reaction. Polymerization - the process of formation of a high molecular weight compound - a polymer - by combining with each other using the main valences of the molecules of the original low molecular weight substance - a monomer. Ethylene polymerization occurs under the action of acids (cationic mechanism) or radicals (radical mechanism):

n CH 2 \u003d CH 2 \u003d - (-CH 2 -CH 2 -) n -.

7. Combustion:

C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

8. Dimerization. Dimerization- the process of formation of a new substance by combining two structural elements(molecules, including proteins, or particles) into a complex (dimer) stabilized by weak and/or covalent bonds.

2CH 2 \u003d CH 2 → CH 2 \u003d CH-CH 2 -CH 3

Application

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 repeated combinations of many small ethylene molecules into larger ones. This process takes place at high pressures and temperatures. The applications for ethylene are numerous. Polyethylene is a polymer that is used especially in large quantities in the production of packaging films, wire coatings 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), ethylene oxide ( antifreeze, polyester fibers and films), acetaldehyde and vinyl chloride. In addition to these compounds, ethylene with benzene forms ethylbenzene, which is used in the production of plastics and synthetic rubber. The substance in question is one of the simplest hydrocarbons. However, the properties of ethylene make it biologically and economically significant.

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

Ethylene is used in glass production special purpose for the automotive industry.

With a friend double bond.

1. Physical properties

Ethylene is a colorless gas with a slight pleasant odour. It is slightly lighter than air. Slightly soluble in water, but soluble in alcohol and other organic solvents.

2. Structure

Molecular formula C 2 H 4. Structural and electronic formulas:

3. Chemical properties

Unlike methane, ethylene is chemically quite active. It is characterized by addition reactions at the site of a double bond, polymerization reactions and oxidation reactions. In this case, one of the double bonds is broken and a simple single bond remains in its place, and due to the dismissed valences, other atoms or atomic groups are attached. Let's look at some examples of reactions. When ethylene is passed into bromine water (an aqueous solution of bromine), the latter becomes colorless as a result of the interaction of ethylene with bromine to form dibromoethane (ethylene bromide) C 2 H 4 Br 2:

As can be seen from the scheme of this reaction, it is not the replacement of hydrogen atoms by halogen atoms, as in saturated hydrocarbons, but the addition of bromine atoms at the site of the double bond. Ethylene also easily discolors the violet color of an aqueous solution with potassium manganate KMnO 4 even at ordinary temperature. At the same time, ethylene itself is oxidized to ethylene glycol C 2 H 4 (OH) 2. This process can be represented by the following equation:

• 2KMnO 4 -> K 2 MnO 4 + MnO 2 + 2O

Reactions between ethylene and bromine and potassium manganate serve to discover unsaturated hydrocarbons. Methane and other saturated hydrocarbons, as already noted, do not interact with potassium manganate.

Ethylene reacts with hydrogen. So, when a mixture of ethylene and hydrogen is heated in the presence of a catalyst (nickel, platinum or palladium powder), they combine to form ethane:

Reactions in which hydrogen is added to a substance are called hydrogenation or hydrogenation reactions. Hydrogenation reactions are of great practical importance. they are quite often used in industry. Unlike methane, ethylene burns in air with a swirling flame, since it contains more carbon than methane. Therefore, not all carbon burns out immediately and its particles become very hot and glow. These carbon particles are then burned in the outer part of the flame:

• C 2 H 4 + 3O 2 \u003d 2CO 2 + 2H 2 O

Ethylene, like methane, forms explosive mixtures with air.

4. Receipt

Ethylene does not occur naturally, except for minor impurities in natural gas. Under laboratory conditions, ethylene is usually obtained by the action of concentrated sulfuric acid on ethyl alcohol when heated. This process can be represented by the following summary equation:

During the reaction, water elements are subtracted from the alcohol molecule, and the two valences saturate each other with the formation of a double bond between carbon atoms. For industrial purposes, ethylene is obtained in large quantities from petroleum cracking gases.

5. Application

In modern industry, ethylene is widely used for the synthesis of ethyl alcohol and the production of important polymeric materials (polyethylene, etc.), as well as for the synthesis of other organic substances. A very interesting property of ethylene is to accelerate the ripening of many garden and garden fruits (tomatoes, melons, pears, lemons, etc.). Using this, fruits can be transported while still green, and then brought to a ripe state already at the place of consumption, introducing small amounts of ethylene into the air of storage rooms.

Ethylene is used to produce vinyl chloride and polyvinyl chloride, butadiene and synthetic rubbers, ethylene oxide and polymers based on it, ethylene glycol, etc.

Notes

Sources

• F. A. Derkach "Chemistry" L. 1968

Answer: Ethylene - key representative a number of unsaturated hydrocarbons with one double bond: formula -
Gas, almost odorless, poorly soluble in water. In air, it burns with a luminous flame. Thanks to the presence
- bonds ethylene easily enters into addition reactions:
(dibromoethane)
(ethyl alcohol) Due to the presence of a double bond, ethylene molecules can combine with each other, forming chains of great length (from many thousands of initial molecules). This reaction is called the polymerization reaction:
Polyethylene is widely used in industry and in everyday life. It is very inactive, does not beat, is well processed. Examples: pipes, containers (barrels, boxes), insulating material, packaging film, glass, toys and much more. Another simple unsaturated hydrocarbon is polypropylene:
During its polymerization, polypropylene is formed - a polymer. The polymer is similar in its cumulative properties and application to polyethylene.

Polypropylene is more durable than polyethylene, so it is used to make many parts for a variety of machines, as well as many precision parts, for example, for escalators. Approximately 40% of polypropylene is processed into fibers.

Ethylene, properties, production, application

Ethylene is a chemical compound described by the formula C2H4. It is the simplest alkene (olefin). It contains a double bond and therefore belongs to unsaturated compounds. Ethene (ethylene) CH2 \u003d CH2, is a colorless gas with a slight odor; Let's well dissolve in diethyl ether and hydrocarbons. The main use of ethylene is as a monomer in the production of polyethylene. Ethylene does not occur in natural gases (with the exception of volcanic gases). It is formed during the pyrogenetic decomposition of many natural compounds containing substances.

Alkynes, structure, properties, preparation. Application

Alkymnes are hydrocarbons containing a triple bond between carbon atoms, with general formula CnH2n-2. Acetylene (Ethine) is the most important chemical raw material. It is used for cutting and welding metals, and for the synthesis of many important products (ethanol, benzene, acetaldehyde, etc.) Alkynes in their physical properties resemble the corresponding alkenes. Lower (up to C4) - gases without color and odor, having more high temperatures boiling points than their counterparts in alkenes. Alkynes are poorly soluble in water, better in organic solvents. The main industrial method for producing acetylene is the electro- or thermal cracking of methane, pyrolysis natural gas and carbide method. The first and main representative of the homologous series of alkynes is acetylene (ethyne).