A prominent representative of unsaturated hydrocarbons is ethene (ethylene). Physical properties: colorless flammable gas, explosive when mixed with oxygen and air. Ethylene is obtained in significant quantities from oil for the subsequent synthesis of valuable organic substances (monohydric and diatomic alcohols, polymers, acetic acid and other compounds).

ethylene, sp 2 hybridization

Hydrocarbons similar in structure and properties to ethene are called alkenes. Historically, another term for this group has been established - olefins. The general formula C n H 2n reflects the composition of the entire class of substances. Its first representative is ethylene, in the molecule of which the carbon atoms form not three, but only two x-bonds with hydrogen. Alkenes are unsaturated or unsaturated compounds, their formula is C 2 H 4. Only 2 p- and 1 s-electron clouds of the carbon atom are mixed in shape and energy; in total, three õ-bonds are formed. This condition is called sp2 hybridization. The fourth valence of carbon is retained, and a π bond appears in the molecule. The structural feature is reflected in the structural formula. But the symbols for designating different types of connections on diagrams are usually the same - dashes or dots. The structure of ethylene determines its active interaction with substances of different classes. The addition of water and other particles occurs due to the rupture of the weak π bond. The released valences are saturated by the electrons of oxygen, hydrogen, and halogens.

Ethylene: physical properties of the substance

Ethene under normal conditions (normal atmospheric pressure and temperature 18°C) is a colorless gas. It has a sweet (ethereal) odor, and its inhalation has a narcotic effect on humans. It hardens at -169.5°C and melts under 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 weak soot. Ethylene dissolves in ether and acetone, much less in water and alcohol. The rounded molar mass of the substance is 28 g/mol. The third and fourth representatives of the homologous series of ethene are also gaseous substances. The physical properties of the fifth and subsequent alkenes are different; they are liquids and solids.

Preparation and properties of ethylene

The German chemist Johann Becher accidentally used it in experiments with concentrated sulfuric acid. This is how ethene was first obtained in laboratory conditions (1680). In the middle of the 19th century A.M. Butlerov gave the compound the name ethylene. The physical properties were also described by the famous Russian chemist. Butlerov proposed a structural formula reflecting the structure of the substance. Methods for obtaining it in the laboratory:

1. Catalytic hydrogenation of acetylene.
2. Dehydrohalogenation of chloroethane in reaction with a concentrated alcohol solution of a strong base (alkali) when heated.
3. The elimination of water from ethyl molecules. The reaction takes place in the presence of sulfuric acid. Its equation: H2C-CH2-OH → H2C=CH2 + H2O

Industrial production:

• oil refining - cracking and pyrolysis of hydrocarbons;
• dehydrogenation of ethane in the presence of a catalyst. H 3 C-CH 3 → H 2 C=CH 2 + H 2

The structure of ethylene explains its typical chemical reactions - the addition of particles by C atoms that are in a multiple bond:

1. Halogenation and hydrohalogenation. The products of these reactions are halogen derivatives.
2. Hydrogenation (saturation of ethane.
3. Oxidation to dihydric alcohol ethylene glycol. Its formula is OH-H2C-CH2-OH.
4. Polymerization according to the scheme: n(H2C=CH2) → n(-H2C-CH2-).

Areas of application of ethylene

When fractionated in large volumes, the physical properties, structure, and chemical nature of the substance allow it to be used in the production of ethyl alcohol, halogen derivatives, alcohols, oxide, acetic acid and other compounds. Ethene is a monomer of polyethylene and also the parent compound for polystyrene.

Dichloroethane, which is produced from ethene and chlorine, is a good solvent used in the production of polyvinyl chloride (PVC). Film, pipes, dishes are made from low- and high-density polyethylene; cases for CDs and other parts are made from polystyrene. PVC is the basis of linoleum and waterproof raincoats. In agriculture, fruits are treated with ethene before harvesting to speed up ripening.

Characteristics and physical properties of ethene

DEFINITION

Ethene (ethylene)- a colorless flammable gas (the structure of the molecule is shown in Fig. 1), with a slight odor. Slightly soluble in water.

Ethene (ethylene) is a colorless flammable gas (the molecular structure is shown in Fig. 1) with a slight odor. Slightly soluble in water. It is highly soluble in diethyl ether and hydrocarbons.

Rice. 1. The structure of the ethylene molecule.

Table 1. Physical properties of ethene.

Obtaining ethene

In industrial quantities, ethene is obtained from oil refining: cracking and dehydrogenation of ethane. Laboratory methods for producing ethylene are presented

— ethanol dehydration

CH 3 -CH 2 -OH →CH 2 =CH 2 + H 2 O (H 2 SO 4 (conc), t o = 170).

— dehydrohalogenation of monohaloethane

CH 3 -CH 2 -Br + NaOH alcohol →CH 2 =CH 2 + NaBr + H 2 O (t o).

— dehalogenation of dihaloethane

Cl-CH 2 -CH 2 -Cl + Zn(Mg) →CH 2 =CH 2 + ZnCl 2 (MgCl 2);

- incomplete hydrogenation of acetylene

CH≡CH + H 2 →CH 2 =CH 2 (Pd, t o).

Chemical properties of ethene

Ethene is a very reactive compound. All chemical transformations of ethylene proceed with splitting:

1. p-C-C bonds (addition, polymerization and oxidation)

• hydrogenation

CH 2 =CH 2 + H 2 → CH 3 -CH 3 (kat = Pt).

• halogenation

CH 2 =CH 2 + Br 2 → BrCH-CHBr.

• hydrohalogenation

CH 2 =CH 2 + H-Cl → H 2 C-CHCl.

• hydration

CH 2 =CH 2 + H-OH → CH 3 -CH 2 -OH (H + , t o).

• polymerization

nCH 2 =CH 2 → -[-CH 2 -CH 2 -]- n (kat, t o).

• oxidation

CH 2 =CH 2 + 2KMnO 4 + 2KOH → HO-CH 2 -CH 2 -OH + 2K 2 MnO 4;

2CH 2 =CH 2 + O 2 → 2C 2 OH 4 (epoxide) (kat = Ag,t o);

2CH 2 =CH 2 + O 2 → 2CH 3 -C(O)H (kat = PdCl 2, CuCl).

1. bonds C sp 3 -H (in the allylic position)

CH 2 =CH 2 + Cl 2 → CH 2 =CH-Cl + HCl (t o =400).

1. Breaking all ties

C 2 H 4 + 2O 2 → 2CO 2 + 2H 2 O.

Applications of ethene

The main use of ethylene is the industrial organic synthesis of compounds such as halogen derivatives, alcohols (ethanol, ethylene glycol), acetaldehyde, acetic acid, etc. In addition, this compound is used in the production of polymers.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

History of the discovery of ethylene

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

CH 3 -CH 2 -OH+H 2 SO 4 →CH 2 =CH 2 +H 2 O

At first it was identified with “flammable air,” i.e., hydrogen. Later, in 1795, ethylene was obtained in a similar way by the Dutch chemists Deyman, Potts van Truswyk, Bond and Lauerenburg and described it under the name “oil gas”, since they discovered the ability of ethylene to add chlorine to form an oily liquid - ethylene chloride (“Dutch oil”). chemists") (Prokhorov, 1978).

The study of the properties of ethylene, its derivatives and homologues began in the mid-19th century. The practical use of these compounds began with the classical studies of A.M. Butlerov and his students in the field of unsaturated compounds and especially Butlerov’s creation of the theory of chemical structure. In 1860, he prepared 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 sprouts, the top of which was bent with a hook and did not bend. In the greenhouse and in the fresh air, the seedlings were even, tall, and the top quickly straightened the hook in the light. Nelyubov proposed that the factor causing the physiological effect was in the air of the laboratory.

At that time, the premises were lit with gas. The same gas burned in the street lamps, and it had long been noticed that in the event of a gas pipeline accident, the trees standing next to the gas leak prematurely turned yellow and shed their leaves.

The illuminating gas contained a variety of organic substances. To remove gas impurities, Nelyubov passed it through a heated tube with copper oxide. In the “purified” air, the pea seedlings developed normally. In order to find out which substance causes the response of the seedlings, Nelyubov added various components of the illuminating gas in turn, and discovered that the addition of ethylene causes:

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

2) “non-bending” apical loop,

3) Changing the orientation of the seedling in space.

This physiological response of seedlings was called the triple response to ethylene. Peas turned out to be so sensitive to ethylene that they began to be used in biotests to determine 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 able to synthesize ethylene, i.e. 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), its inhalation has a narcotic effect on humans. Ethylene dissolves in ether and acetone, much less in water and alcohol. Forms an explosive mixture when mixed with air

It hardens at –169.5°C and melts under 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 weak soot. The rounded molar mass of the substance is 28 g/mol. The third and fourth representatives of the homologous series of ethene are also gaseous substances. The physical properties of the fifth and subsequent alkenes are different; they are liquids and solids.

Ethylene production

The main methods for producing ethylene:

Dehydrohalogenation of halogenated alkanes under the influence 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 influence of active metals

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

Dehydration of ethylene by heating it with sulfuric acid (t >150˚ C) or passing its vapor over a catalyst

CH 3 -CH 2 -OH → CH 2 = CH 2 + H 2 O;

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

CH 3 -CH 3 → CH 2 = CH 2 + H 2.

Chemical properties of ethylene

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

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

CH 2 = CH 2 + Br 2 = Br-CH 2 -CH 2 Br.

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:

CH 2 = CH 2 + Cl 2 → CH 2 = CH-Cl + HCl.

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

CH 2 = CH 2 + HCl → CH 3 -CH 2 -Cl.

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

CH 2 = CH 2 + H 2 O → CH 3 -CH 2 -OH.

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

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

CH 2 = 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 = CH 2 + BH 3 → CH 3 -CH 2 -BH 2 (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,

2 ON-CH = CH 2 + HCN → 2 ON-CH 2 -CH 2 -CN.

4. 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. As a result, ethylene glycol is formed

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

At severe oxidation ethylene with a boiling solution of potassium permanganate in an acidic environment, a complete rupture of the bond (σ-bond) occurs 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 = CH 2 +1/2O 2 = CH 3 -CH = O.

5. hydrogenation. At restoration Ethylene produces 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 occur is the presence of catalysts (Ni, Pd, Pt), as well as heating of the reaction mixture:

CH 2 = CH 2 + H 2 = CH 3 -CH 3.

6. Ethylene enters 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):

n CH 2 = CH 2 = -(-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 =CH 2 →CH 2 =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 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 ( technical alcohol), ethylene oxide ( antifreeze, polyester fibers and films), acetaldehyde and vinyl chloride. In addition to these compounds, ethylene and benzene form 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 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. In addition, 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.

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

Hydrocarbons

Grade 10

Continuation. See the beginning in No. 9/2009.

Lecture 3.
Unsaturated hydrocarbons of the ethylene series, general composition formula. Electronic and spatial structure, chemical properties of ethylene

Unsaturated hydrocarbons of the ethylene series, or alkenes, are hydrocarbons with the general formula C n H 2 n, whose molecules contain one double bond. C atoms connected by a double bond are in the state sp

2-hybridization, the double bond is a combination of - and - bonds. By its nature, -connection is sharply different from -connection; - the bond is less strong due to the overlap of electron clouds outside the plane of the molecule. The simplest alkene is ethylene

. The structural and electronic formulas of ethylene are: In the ethylene molecule one undergoes hybridization s- and two C atoms connected by a double bond are in the state p s-orbitals of C atoms ( The structural and electronic formulas of ethylene are: 2 -hybridization). s Thus, each C atom has three hybrid orbitals and one non-hybrid

The ethylene molecule is symmetrical; the nuclei of all atoms are located in the same plane and bond angles are close to 120°; the distance between the centers of C atoms is 0.134 nm.

If atoms are connected by a double bond, then their rotation is impossible without the electron clouds opening the bonds.

Ethylene is the first member of the homologous series of alkenes.

But the butene-2 ​​molecule can be in the form of two spatial forms - cis- and trans-:

Cis- and trans-isomers, having different arrangements of atoms in space, differ in many physical and chemical properties.

Thus, two types are possible for alkenes structural isomerism: carbon chain isomerism and double bond position isomerism. It is also possible geometric isomerism.

Ethylene (ethene) is a colorless gas with a very faint sweetish odor, slightly lighter than air, slightly soluble in water.

By chemical The properties of ethylene differ sharply from ethane, which is due to the electronic structure of its molecule. Having a double bond in the molecule, consisting of - and - bonds, ethylene is capable of attaching two monovalent atoms or radicals due to the cleavage of the - bond.

Ability to react accession characteristic of all alkenes.

1. Hydrogen addition(hydrogenation reaction):

2. Addition of halogens(halogenation reaction):

When bromine (in the form of bromine water) is added to an alkene, the brown color of bromine quickly disappears. This reaction is qualitative for a double bond.

3. (hydrohalogenation reaction):

If the starting alkene is unsymmetrical, then the reaction proceeds according to Markovnikov’s rule.

The addition of hydrogen halides to unsaturated compounds occurs according to ionic mechanism.

4. Water connection(hydration reaction):

This reaction is used to produce ethyl alcohol in industry.

Alkanes are characterized by reactions oxidation :

1. Ethylene is easily oxidized even at ordinary temperatures, for example, under the action of potassium permanganate. If ethylene is passed through an aqueous solution of potassium permanganate KMnO4, then the characteristic violet color of the latter disappears, and ethylene is oxidized (hydroxylation reaction) with potassium permanganate (qualitative reaction to a double bond):

2. Ethylene burns with a luminous flame to form carbon monoxide (IV) and water:

C 2 H 4 + 3O 2 -> 2CO 2 + 2H 2 O.

3. The partial oxidation of ethylene by atmospheric oxygen is of great industrial importance:

Ethylene, like all unsaturated hydrocarbons, is characterized by reactions polymerization .

Polymerization is the sequential combination of identical molecules into larger ones.

Thus, ethylene and its homologues are characterized by addition, oxidation and polymerization reactions.

Lecture 4.
Acetylene is a representative of hydrocarbons with a triple bond in the molecule.
Chemical properties, production and use of acetylene in organic synthesis

Alkynes are hydrocarbons with the general formula C n H 2 n–2, molecules of which contain one triple bond.

Acetylene– the first member of the homologous series of acetylene hydrocarbons, or alkynes.

The molecular formula of acetylene is C 2 H 2. = Structural formula of acetylene H–C

C–H.

Electronic formula: : H : : : H : WITH

N. C atoms connected by a double bond are in the state Acetylene carbon atoms linked by a triple bond are in the state The structural and electronic formulas of ethylene are:-hybridization. s When acetylene molecules are formed, one C atom hybridizes at each s- And The structural and electronic formulas of ethylene are:-orbitals. s As a result, each C atom acquires two hybrid orbitals, and two s-orbitals remain non-hybrid. The two hybrid orbitals overlap each other, and an -bond is formed between the C atoms.

The remaining two hybrid orbitals overlap with

-orbitals of H atoms, and -bonds are also formed between them and C atoms. Four non-hybrid

-orbitals are placed mutually perpendicular and perpendicular to the directions of -bonds. In these planes-orbitals mutually overlap, and two -bonds are formed, which are relatively weak and are easily broken in chemical reactions.

Thus, in an acetylene molecule there are three -bonds (one C–C bond and two C–H bonds) and two -bonds between two C atoms. The triple bond in alkynes is not a triple bond, but a combined bond, consisting of three bonds: one - and two - bonds.

The acetylene molecule has a linear structure. accession. The appearance of the third bond causes the C atoms to move further closer together: the distance between their centers is 0.120 nm.

1. Hydrogen addition Physical properties.

2. Addition of halogens Acetylene is a colorless gas, lighter than air, slightly soluble in water, and in its pure form almost odorless.

Bromine water becomes discolored.

3. Discoloration of bromine water is a qualitative reaction to acetylene, as well as to all unsaturated hydrocarbons. Addition of hydrogen halides

(hydrohalogenation reaction). The addition reaction of hydrogen chloride is important:

4. Water connection A polymer, polyvinyl chloride, is obtained from vinyl chloride.

(hydration reaction) occurs in the presence of mercury(II) salts - HgSO 4, Hg(NO 3) 2 - with the formation of acetaldehyde:

The acetylene molecule has a linear structure. oxidation This reaction is named after the Russian scientist Mikhail Grigorievich Kucherov (1881).

1. . Acetylene is very sensitive to oxidizing agents.

When passed through a solution of potassium permanganate, acetylene is easily oxidized, and the KMnO 4 solution becomes discolored:

Discoloration of potassium permanganate can be used as a qualitative reaction to the triple bond.

Oxidation usually involves the cleavage of the triple bond and the formation of carboxylic acids: = R–C

C–R " + 3[O] + H 2 O -> R–COOH + R " –COOH.

Acetylene upon complete combustion produces carbon monoxide (IV) and water:

2C 2 H 2 + 5O 2 -> 4CO 2 + 2H 2 O.

In air, acetylene burns with a highly smoky flame. Reactions polymerization

1. . Under certain conditions, acetylene can polymerize into benzene and vinyl acetylene.

2. When acetylene is passed over activated carbon at 450–500 °C, acetylene trimerizes to form benzene (N.D. Zelinsky, 1927):

Under the influence of an aqueous solution of CuCl and NH 4 Cl, acetylene dimerizes, forming vinyl acetylene:

Vinylacetylene is highly reactive; By adding hydrogen chloride, it forms chloroprene, which is used to produce artificial rubber: Preparation of acetylene.

In the laboratory and in industry, acetylene is produced by reacting calcium carbide with water (carbide method):

Calcium carbide is produced in electric furnaces by heating coke with quicklime:

A lot of energy is spent on producing CaC 2, so the carbide method cannot meet the needs for acetylene.

In industry, acetylene is obtained as a result of high-temperature cracking of methane: Application of acetylene in organic synthesis.

Examples of industrial uses of acetylene:

Lecture 5.
Diene hydrocarbons, their structure, properties, preparation and practical significance

Diene hydrocarbons, or alkadienes, are hydrocarbons containing two double bonds in the carbon chain. Their composition can be expressed by the general formula C n H 2 n–2. They are isomeric to acetylene hydrocarbons.

Alkadienes, in whose molecules the double bonds are separated by a single bond (conjugated double bonds), are widely used - these are

which are the starting materials for the production of rubbers.

To form two double bonds in one molecule, at least three C atoms are required. The simplest representative of alkadienes is propadiene CH 2 =C=CH 2.

Diene hydrocarbons can differ in the position of the double bond in the carbon chain:

Isomerism of the carbon chain is also possible.

Butadiene-1,3 is the simplest conjugated alkadiene. In butadiene-1,3, all four C atoms are in the state C atoms connected by a double bond are in the state 2-hybridization. s They lie in the same plane and form the skeleton of the molecule. Non-hybrid s-orbitals of each C atom are perpendicular to the skeletal plane and parallel to each other, which creates conditions for their mutual overlap. Overlap occurs not only between the C 1 – C 2 and C 3 – C 4 atoms, but also partially between the C 2 – C 3 atoms.

-orbitals are placed mutually perpendicular and perpendicular to the directions of -bonds. In these planes When four overlap -orbitals, a single -electron cloud is formed, i.e. conjugation of two double bonds (, -conjugation). -orbitals, a single -electron cloud is formed, i.e. Butadiene-1,3 under normal conditions is a gas that liquefies when

Thus, in an acetylene molecule there are three -bonds (one C–C bond and two C–H bonds) and two -bonds between two C atoms. t

= 4.5 °C; 2-methylbutadiene-1,3 is a volatile liquid that boils at accession = 34.1 °C.

Diene hydrocarbons with conjugated double bonds are highly reactive.

They react easily

, reacting with hydrogen, halogens, hydrogen halides, etc.

Usually the addition occurs at the ends of diene molecules. Thus, when interacting with bromine, double bonds are broken, bromine atoms are added to the outermost C atoms, and free valences form a double bond, i.e. As a result of the addition, the double bond moves:

If there is an excess of bromine, another molecule can be added at the site of the remaining double bond.

In alkadienes, addition reactions can proceed in two directions:

Due to the presence of double bonds, diene hydrocarbons are quite easily polymerize .

The product of polymerization of 2-methylbutadiene-1,3 (isoprene) is polyisoprene - an analogue of natural rubber: Receipt.

The catalytic method for producing 1,3 butadiene from ethanol was discovered in 1932 by Sergei Vasilievich Lebedev. According to Lebedev's method, butadiene-1,3 is obtained as a result of simultaneous dehydrogenation and dehydration of ethanol in the presence of catalysts based on ZnO and Al 2 O 3: -orbitals, a single -electron cloud is formed, i.e. But a more promising method for producing butadiene is the dehydrogenation of butane contained in petroleum gases. At

= 600 °C, stepwise dehydrogenation of butane occurs in the presence of a catalyst:

The catalytic dehydrogenation of isopentane produces isoprene: Practical significance.

Diene hydrocarbons are mainly used for the synthesis of rubbers:

Polymerization reaction of butadiene-1,3:

Reprinted with continuation

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 sweet, 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 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 especially in large quantities 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 useful 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.