DEFINITION

Ethylene (ethene)- the first representative of the homologous series of alkenes (unsaturated hydrocarbons with one double bond).

Structural formula:

Gross formula: C 2 H 4 . Molar mass - 28 g/mol.

Ethylene is a colorless gas with a slight odor. Density 1.178 kg/m 3 (lighter than air). Combustible. Slightly soluble in water, but good in diethyl ether and hydrocarbons.

The electronic structure of the ethylene molecule

The carbon atoms in an alkene molecule are linked by a double bond. These atoms are in the state of sp 2 hybridization. The double bond between them is formed from two pairs of shared electrons, i.e. it is a four-electron bond. It is a combination of covalent σ-bonds and π-bonds. The σ bond is formed due to the axial overlap of the sp2 hybrid orbitals, and the π bond is due to the lateral overlap of the unhybridized p orbitals of two carbon atoms (Fig. 1).

Rice. 1. The structure of the ethylene molecule.

Five σ-bonds of two sp 2 -hybridized carbon atoms lie in the same plane at an angle of 120 o and make up the σ-skeleton of the molecule. Above and below this plane, the electron density of the π-bond is symmetrically located, which can also be depicted as a plane perpendicular to the σ-skeleton.

When a π-bond is formed, carbon atoms approach each other, because the internuclear space in a double bond is more saturated with electrons than in a σ-bond. This contracts the atomic nuclei and therefore the length of the double bond (0.133 nm) is less than the single bond (0.154 nm).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Physical properties of ethylene:
Ethylene is a colorless gas with a slight odor, slightly soluble in water, soluble in alcohol, and readily soluble in diethyl ether. Forms an explosive mixture when mixed with air.
Chemical properties of ethylene:
Ethylene is characterized by reactions proceeding by the mechanism of electrophilic, addition, radical substitution reactions, oxidation, reduction, and polymerization.

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

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

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:

CH2 = CH2 + Cl2 → CH2 = CH-Cl + HCl.

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

CH2 = CH2 + HCl → CH3-CH2-Cl.

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

CH2 \u003d CH2 + H2O → CH3-CH2-OH.

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

2ON-CH = CH2 + HCN → 2ON-CH2-CH2-CN.

In the course of ethylene oxidation reactions, the formation of various products is possible, and the composition is determined by the conditions of the oxidation. Thus, during the oxidation of ethylene under mild conditions (the oxidizing agent is potassium permanganate), the π-bond breaks and the formation of dihydric alcohol - ethylene glycol occurs:

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

During the hard oxidation of ethylene with a boiling solution of potassium permanganate in an acidic medium, the bond (σ-bond) is completely broken 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 \u003d CH2 + 1 / 2O2 \u003d CH3-CH \u003d O.

When ethylene is reduced, ethane, a representative of the alkane class, is formed. 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:

CH2 = CH2 + H2 = CH3-CH3.

Ethylene enters the 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).

To the question, tell me the formula of ethene and ethylene given by the author Elena Dmitrieva the best answer is Ethylene - С2Н4
You can get it from glucose like this.
1. Fermentation of glucose leads to the formation of ethyl alcohol.
2. Ethylene is obtained by dehydration of ethyl alcohol.
Ethylene (another name is ethene) is a chemical compound described by the formula C2H4. Ethylene is almost never found in nature. It is a colorless flammable gas with a slight odor. Partially soluble in water (25.6 ml in 100 ml of water at 0°C), ethanol (359 ml under the same conditions). It dissolves well in diethyl ether and hydrocarbons.
Ethylene is the simplest alkene (olefin). It contains a double bond and therefore belongs to unsaturated compounds. It plays an extremely important role in industry, and is also a phytohormone.
Raw materials for polyethylene and more
Ethylene is the most produced organic compound in the world; the total world production of ethylene in 2005 was 107 million tons and continues to grow by 4–6% per year. The source of industrial production of ethylene is the pyrolysis of various hydrocarbon raw materials, for example, ethane, propane, butane, contained in the associated gases of oil production; from liquid hydrocarbons - low-octane fractions of direct distillation of oil. Ethylene yield is about 30%. Simultaneously, propylene and a number of liquid products (including aromatic hydrocarbons) are formed.
Ethylene chlorination produces 1,2-dichloroethane, hydration leads to ethyl alcohol, interaction with HCl leads to ethyl chloride. When ethylene is oxidized with atmospheric oxygen in the presence of a catalyst, ethylene oxide is formed. In liquid-phase catalytic oxidation with oxygen, acetaldehyde is obtained, under the same conditions in the presence of acetic acid, vinyl acetate is obtained. Ethylene is an alkylating agent, for example, under Friedel-Crafts reaction conditions, it is able to alkylate benzene and other aromatic compounds. Ethylene is able to polymerize in the presence of catalysts both independently and act as a comonomer, forming a wide range of polymers with different properties.
Application
Ethylene is one of the basic products of industrial chemistry and is at the base of a number of synthesis chains. The main use of ethylene is as a monomer in the production of polyethylene (the largest polymer in the world production). Depending on the polymerization conditions, low-pressure polyethylene and high-pressure polyethylene are obtained.
Polyethylene is also used for the production of a number of copolymers, including those with propylene, styrene, vinyl acetate, and others. Ethylene is the raw material for the production of ethylene oxide; as an alkylating agent - in the production of ethylbenzene, diethylbenzene, triethylbenzene.
Ethylene is used as a starting material for the production of acetaldehyde and synthetic ethyl alcohol. It is also used for the synthesis of ethyl acetate, styrene, vinyl acetate, vinyl chloride; in the production of 1,2-dichloroethane, ethyl chloride.
Ethylene is used to accelerate the ripening of fruits - for example, tomatoes, melons, oranges, tangerines, lemons, bananas; defoliation of plants, reducing pre-harvest abscission of fruits, to reduce the strength of attachment of fruits to mother plants, which facilitates mechanized harvesting.
In high concentrations, ethylene has a narcotic effect on humans and animals.

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

Unsaturated hydrocarbons with a double chemical bond in molecules belong to the group of alkenes. The first representative of the homologous series is ethene, or ethylene, whose formula is: C 2 H 4 . Alkenes are often referred to as olefins. The name is historical and originated in the 18th century, after obtaining the product of the interaction of ethylene with chlorine - ethyl chloride, which looks like an oily liquid. Then ethene was called oil-producing gas. In our article, we will study its chemical properties, as well as its production and application in industry.

The relationship between the structure of the molecule and the properties of the substance

According to the theory of the structure of organic substances proposed by M. Butlerov, the characteristic of a compound depends entirely on the structural formula and the type of bonds of its molecule. The chemical properties of ethylene are also determined by the spatial configuration of atoms, the hybridization of electron clouds, and the presence of a pi bond in its molecule. Two unhybridized p-electrons of carbon atoms overlap in a plane perpendicular to the plane of the molecule itself. A double bond is formed, the rupture of which determines the ability of alkenes to undergo addition and polymerization reactions.

Physical Properties

Ethene is a gaseous substance with a subtle peculiar smell. It is poorly soluble in water, but readily soluble in benzene, carbon tetrachloride, gasoline and other organic solvents. Based on the formula of ethylene C 2 H 4, its molecular weight is 28, that is, ethene is slightly lighter than air. In the homologous series of alkenes, with an increase in their mass, the aggregate state of substances changes according to the scheme: gas - liquid - solid compound.

Gas production in laboratory and industry

By heating ethyl alcohol to 140°C in the presence of concentrated sulfuric acid, ethylene can be obtained in the laboratory. Another way is the splitting off of hydrogen atoms from alkane molecules. By acting with caustic sodium or potassium on halogen-substituted compounds of saturated hydrocarbons, for example, on chloroethane, ethylene is produced. In industry, the most promising way to obtain it is the processing of natural gas, as well as the pyrolysis and cracking of oil. All chemical properties of ethylene - reactions of hydration, polymerization, addition, oxidation - are explained by the presence of a double bond in its molecule.

Interaction of olefins with elements of the main subgroup of the seventh group

All members of the ethene homologous series attach halogen atoms at the site of the pi-bond break in their molecule. So, an aqueous solution of red-brown bromine becomes colorless, resulting in the formation of the equation ethylene - dibromoethane:

C 2 H 4 + Br 2 \u003d C 2 H 4 Br 2

The reaction with chlorine and iodine proceeds similarly, in which the addition of halogen atoms also occurs at the site of the destruction of the double bond. All compounds - olefins can interact with hydrogen halides: hydrogen chloride, hydrogen fluoride, etc. As a result of the addition reaction proceeding according to the ionic mechanism, substances are formed - halogen derivatives of saturated hydrocarbons: chloroethane, fluoroethane.

Industrial production of ethanol

The chemical properties of ethylene are often used to obtain important substances widely used in industry and everyday life. For example, by heating ethene with water in the presence of phosphoric or sulfuric acids, a hydration process occurs under the action of a catalyst. It goes with the formation of ethyl alcohol - a large-tonnage product obtained at chemical enterprises of organic synthesis. The mechanism of the hydration reaction proceeds by analogy with other addition reactions. In addition, the interaction of ethylene with water also occurs as a result of breaking the pi bond. Hydrogen atoms and a hydroxo group, which are part of the water molecule, are added to the free valences of the carbon atoms of ethene.

Hydrogenation and combustion of ethylene

Despite all of the above, the hydrogen compound reaction is of little practical importance. However, it shows the genetic relationship between different classes of organic compounds, in this case alkanes and olefins. By adding hydrogen, ethene is converted to ethane. The opposite process - the splitting off of hydrogen atoms from saturated hydrocarbons leads to the formation of a representative of alkenes - ethene. Rigid oxidation of olefins, called combustion, is accompanied by the release of a large amount of heat, the reaction is exothermic. Combustion products are the same for substances of all classes of hydrocarbons: alkanes, unsaturated compounds of the ethylene and acetylene series, aromatic substances. These include carbon dioxide and water. Air reacts with ethylene to form an explosive mixture.

Oxidation reactions

Ethene can be oxidized with potassium permanganate solution. This is one of the qualitative reactions, with the help of which they prove the presence of a double bond in the composition of the analyte. The violet color of the solution disappears due to the rupture of the double bond and the formation of a dihydric saturated alcohol - ethylene glycol. The reaction product has a wide range of applications in industry as a raw material for the production of synthetic fibers, such as lavsan, explosives and antifreeze. As you can see, the chemical properties of ethylene are used to obtain valuable compounds and materials.

Olefin polymerization

An increase in temperature, an increase in pressure and the use of catalysts are necessary conditions for carrying out the polymerization process. Its mechanism is different from addition or oxidation reactions. It represents the sequential binding of many ethylene molecules at the sites of double bond breakage. The reaction product is polyethylene, the physical characteristics of which depend on the value of n - the degree of polymerization. If it is small, then the substance is in a liquid state of aggregation. If the indicator approaches 1000 links, then polyethylene film and flexible hoses are made from such a polymer. If the degree of polymerization exceeds 1500 links in the chain, then the material is a white solid, oily to the touch.

It goes to the manufacture of solid products and plastic pipes. Teflon, a halogenated compound of ethylene, has non-stick properties and is a widely used polymer that is in demand in the manufacture of multicookers, frying pans, and braziers. Its high ability to resist abrasion is used in the production of lubricants for automobile engines, and its low toxicity and tolerance to human tissues have made it possible to use Teflon prostheses in surgery.

In our article, we considered such chemical properties of olefins as ethylene combustion, addition reactions, oxidation and polymerization.