Ethylene bond. Chemical properties of ethylene

DEFINITION

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

Formula - C 2 H 4 (CH 2 \u003d CH 2). Molecular weight (mass of one mol) - 28 g / mol.

The hydrocarbon radical formed from ethylene is called vinyl (-CH = CH 2). The carbon atoms in the ethylene molecule are in sp 2 hybridization.

Chemical properties of ethylene

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

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.

Hydrohalogenation- the 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.

Hydration- interaction of ethylene with water in the presence of mineral acids (sulfuric, 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.

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

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.

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.

Ethylene enters 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 -.

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

Ethylene production

The main methods for producing ethylene:

— dehydrohalogenation of halogen derivatives of alkanes under the action of alcohol 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;

- dehydration of ethylene when it is heated with sulfuric acid (t > 150 C) or when its vapor is passed over the 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.

Application of ethylene

Ethylene is one of the most important compounds produced in huge industrial scale. It is used as a raw material for the production of a whole range of different organic compounds (ethanol, ethylene glycol, acetic acid, etc.). Ethylene serves as a feedstock for the production of polymers (polyethylene, etc.). It is used as a substance that accelerates the growth and ripening of vegetables and fruits.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Physical Properties

Ethan at n. y.- colorless gas, odorless. Molar mass - 30.07. Melting point -182.81 °C, boiling point -88.63 °C. . Density ρ gas. \u003d 0.001342 g / cm³ or 1.342 kg / m³ (n.a.), ρ fl. \u003d 0.561 g / cm³ (T \u003d -100 ° C). Dissociation constant 42 (in water, acc.) [ source?] . Vapor pressure at 0 ° C - 2.379 MPa.

Chemical properties

Chemical formula C 2 H 6 (rational CH 3 CH 3). The most characteristic reactions are the substitution of hydrogen by halogens, which proceed according to the free radical mechanism. Thermal dehydrogenation of ethane at 550-650 °C leads to ketene, at temperatures above 800 °C to catacetylene (benzolysis is also formed). Direct chlorination at 300-450 ° C - to ethyl chloride, nitration in the gas phase gives a mixture (3: 1) of nitroethane-nitromethane.

Receipt

In industry

In industry, it is obtained from petroleum and natural gases, where it is up to 10% by volume. In Russia, the content of ethane in petroleum 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 vitro

Obtained from iodomethane by the Wurtz reaction, from sodium acetate by electrolysis by the Kolbe reaction, by fusing 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) - class organic compound alkanes. In chemistry, the name is mainly used to refer to n-butane. The same name has a mixture of n-butane and its isomer isobutane CH(CH3)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 apparatus. Contained in natural gas, is formed when cracking oil products, when separating the associated petroleum gas, "fatty" natural gas. As a representative of hydrocarbon gases, it is flammable and explosive, has low toxicity, has a specific characteristic odor, and has narcotic properties. According to the degree of impact on the body, the gas belongs to substances of the 4th hazard class (low-hazardous) according to GOST 12.1.007-76. Harmful effect on nervous system .

isomerism

Bhutan 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, it dissolves much better 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. In the laboratory can be obtained from wurtz reactions.

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

Desulfurization (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 of cleaning the butane fraction from mercaptans consists in alkaline extraction of mercaptans from the hydrocarbon fraction and subsequent regeneration of alkali in the presence of homogeneous or heterogeneous catalysts with atmospheric oxygen with the release of disulfide oil.

Applications and reactions

With free radical chlorination, it forms a mixture of 1-chloro- and 2-chlorobutane. Their ratio is well explained by the difference in strength S-H ties in positions 1 and 2 (425 and 411 kJ/mol). Complete combustion in air forms carbon dioxide and water. Butane is used in combination 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. The calorific value of 1 kg is 45.7 MJ (12.72 kWh).

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

In the absence 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

firm dupont developed a method for obtaining maleic anhydride from n-butane during 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 applications. The performance of such systems is slightly lower than freon ones. Butane is environmentally friendly, unlike freon refrigerants.

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

Ethylene(on IUPAC: ethene) - organic chemical compound, described by the formula C 2 H 4 . Is the simplest alkene (olefin). Ethylene is practically not 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. Contains a double bond and is therefore classified as unsaturated or unsaturated hydrocarbons. Plays an extremely important role in the industry, and is also phytohormone. Ethylene is the most produced organic compound in the world ; total world production of ethylene 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 obtain 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 up to the mid-1980s in the USSR and the Middle East. Ethylene is phytohormone almost all plants , among others 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, less strong, is easily broken, and at the place of the bond breaking, the molecules are joined, oxidized, and polymerized.

Halogenation:

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

Bromine water becomes decolorized. it qualitative reaction for unrestricted connections.

Hydrogenation:

CH 2 \u003d CH 2 + H - H → CH 3 - CH 3 (under the action of Ni)

Hydrohalogenation:

CH 2 \u003d CH 2 + HBr → CH 3 - CH 2 Br

Hydration:

CH 2 \u003d CH 2 + HOH → CH 3 CH 2 OH (under the action of a catalyst)

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

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.

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

C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

Polymerization:

nCH 2 \u003d CH 2 → (-CH 2 -CH 2 -) n

Isoprene CH 2 \u003d C (CH 3) -CH \u003d CH 2, 2-methylbutadiene-1,3 - unsaturated hydrocarbon diene series (C n H 2n−2 ) . AT normal conditions colorless liquid. He is monomer for natural rubber and a structural unit for many other molecules natural compounds- isoprenoids, or terpenoids. . Soluble in alcohol. Isoprene polymerizes to give isoprene rubbers. Isoprene also reacts polymerization with vinyl connections.

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. It contains a few percent of other materials as impurities, such as squirrels, fatty acid, resin 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) The annual production of isoprene by vegetation is about 600 million tons, half of which is produced by tropical broadleaf trees, the rest is produced by shrubs. After exposure to the atmosphere, isoprene is converted by free radicals (such as the hydroxyl (OH) radical) and, to a lesser extent, ozone into various substances such as aldehydes, hydroxyperoxides, organic nitrates and epoxies, 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 commercially available as a product of thermal cracking naphtha or oils, as well as a by-product in the production ethylene. Approximately 20,000 tons per year are produced. 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 \u003d CH-CH \u003d CH 2 - 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 allowable concentration in air (MAC) 0.1 g/m³, density 0.650 g/cm³ at -6 °C.

We will slightly dissolve in water, we will well dissolve in alcohol, kerosene with air in an amount of 1.6-10.8%.

Chemical properties

Butadiene tends to polymerization, easily oxidized air with education peroxide compounds that accelerate polymerization.

Receipt

Butadiene is obtained by the reaction Lebedev 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 \u003d CH-CH 2 -CH 3 → CH 2 \u003d CH-CH \u003d CH 2 + H 2

Application

The polymerization of butadiene produces a synthetic rubber. Copolymerization with acrylonitrile and styrene receive ABS plastic.

Benzene (C 6 H 6 , Ph H) - organic chemical compound , colorless liquid with a pleasant sweetness smell. Protozoa aromatic hydrocarbon. Benzene is part of gasoline, widely used in industry, is the raw material for the production medicines, various plastics, synthetic rubber, dyes. Although benzene is part of 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 forms a lot of soot. Forms explosive mixtures with air, mixes well with ethers, gasoline and other organic solvents, with water forms an azeotropic mixture with a boiling point of 69.25 ° C (91% benzene). Solubility in water 1.79 g/l (at 25 °C).

Chemical properties

Substitution reactions are characteristic of benzene - benzene reacts with alkenes, chlorine alkanes, halogens, nitric and sulfuric acid. Benzene ring cleavage reactions take place under harsh conditions (temperature, pressure).

Interaction with chlorine in the presence of a catalyst:

C 6 H 6 + Cl 2 -(FeCl 3) → C 6 H 5 Cl + HCl forms chlorobenzene

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, when heated or illuminated, a radical substitution reaction occurs.

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

Interaction 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 classified as unsaturated hydrocarbons(homologous series C n H 2n-6), but unlike hydrocarbons of the series ethylene C 2 H 4 exhibits properties inherent in 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 idea 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

To date, there are three fundamentally different methods for the production of benzene.

Coking coal. This process was historically the first and served as the main source of benzene until World War II. At present, the proportion of benzene obtained 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 US. AT Western Europe, Russia and Japan in this way receive 40-60% of total substances. 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;

Pyrolysis gasoline and heavier oil 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 resulting benzene 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);

  about 10-15% benzene hydrogenate in cyclohexane;

  about 10% of benzene is used for production nitrobenzene;

  2-3% benzene is converted into linear alkylbenzenes;

  approximately 1% benzene is used for synthesis chlorobenzene.

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

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

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

general characteristics

Colorless mobile volatile liquid with a pungent odor, exhibits a weak narcotic effect. Miscible to an unlimited extent with hydrocarbons, many alcohols and ethers, not miscible with water. Refractive index light 1.4969 at 20 °C. Combustible, burns with a smoky flame.

Chemical properties

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

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

In addition to substitution reactions, toluene enters into addition reactions (hydrogenation), ozonolysis. Some oxidizing agents (an alkaline solution of potassium permanganate, dilute nitric acid) oxidize the methyl group to a carboxyl group. Auto-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:

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

Receiving and cleaning

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

Toluene can be obtained from benzene 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 a component of various commercial solvents for varnishes and colors. 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 a characteristic smell. It does not dissolve in water, but it is good - in benzene, broadcast, alcohol, chloroform.

Chemical properties

Naphthalene is chemically similar to benzene: easily nitrated, 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 about 30 mg/l, flash point 79 - 87 °C, autoignition point 525 °C, molar mass 128.17052 g/mol.

Receipt

Get naphthalene from coal tar. Also, naphthalene can be isolated from heavy pyrolysis tar (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 the synthesis phthalic anhydride, tetralin, decalina, various derivatives of naphthalene.

Naphthalene derivatives are used to obtain dyes and explosives, in medicine, how insecticide.

Or ethene(IUPAC) - C 2 H 4, the simplest and most important representative 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 soluble in alcohol and other organic solvents.

Structure

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

Structural formula of ethylene

Electronic formula of ethylene

Chemical properties

Unlike methane, ethylene is chemically rather 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 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 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 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, 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.

Encyclopedic YouTube

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  Ethylene began to be widely used as a monomer before the Second World War due to the need to obtain a high-quality insulating material that could replace polyvinyl chloride. After the development of a method for the polymerization of ethylene under high pressure and studying the dielectric properties of the resulting polyethylene, its production began, first in the UK, and later in other countries.

  Main industrial method Ethylene production is the pyrolysis of liquid distillates of petroleum or lower saturated hydrocarbons. The reaction is carried out in tube furnaces at +800-950 °C and a pressure of 0.3 MPa. When straight-run gasoline is used as a raw material, the ethylene yield is approximately 30%. Simultaneously with ethylene, a significant amount of liquid hydrocarbons, including aromatic ones, is also formed. During the pyrolysis of gas oil, the yield of ethylene is approximately 15-25%. The highest yield of ethylene - up to 50% - is achieved when saturated hydrocarbons are used as raw materials: ethane, propane and butane. Their pyrolysis is carried out in the presence of steam.

  When released from production, during commodity accounting operations, when checking it for compliance with regulatory and technical documentation, ethylene samples are taken according to the procedure described in GOST 24975.0-89 “Ethylene and propylene. Sampling methods". Ethylene sampling can be carried out both in gaseous and liquefied form in special samplers in accordance with GOST 14921.

  Ethylene produced industrially in Russia must comply with the requirements set forth in GOST 25070-2013 “Ethylene. Specifications".

  Production structure

  Currently, in the structure of ethylene production, 64% falls on large-tonnage pyrolysis plants, ~17% - on small-tonnage gas pyrolysis plants, ~11% is gasoline pyrolysis, and 8% falls on ethane pyrolysis.

  Application

  Ethylene is the leading product of the main organic synthesis and is used to obtain the following compounds (listed in alphabetical order):

  • 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);

  Ethylene mixed with oxygen was used in medicine for anesthesia until the mid-1980s in the USSR and the Middle East. Ethylene is a phytohormone in almost all plants, among other things, it is responsible for the fall of needles in conifers.

  Electronic and spatial structure of the molecule

  The carbon atoms are in the second valence state(sp 2 hybridization). As a result, three hybrid clouds are formed on the plane at an angle of 120°, which form three σ-bonds with carbon and two hydrogen atoms; p-electron, which did not participate in hybridization, forms a π-bond with the p-electron of the neighboring carbon atom in the perpendicular plane. This forms a double bond between carbon atoms. The molecule has a planar structure.

  CH 2 \u003d CH 2

  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, less strong, is easily broken, and at the place of the bond breaking, the molecules are joined, oxidized, and polymerized.

  • Halogenation:
  CH 2 \u003d CH 2 + Br 2 → CH 2 Br-CH 2 Br Bromine water becomes decolorized. This is a qualitative reaction to unsaturated compounds.
  • Hydrogenation:
  CH 2 \u003d CH 2 + H - H → CH 3 - CH 3 (under the action of Ni)
  • Hydrohalogenation:
  CH 2 \u003d CH 2 + HBr → CH 3 - CH 2 Br
  • Hydration:
  CH 2 \u003d CH 2 + HOH → CH 3 CH 2 OH (under the action of a catalyst) This reaction was discovered by A.M. Butlerov, and it is used for the industrial production of ethyl alcohol.
  • 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. Reaction equation: 3CH 2 \u003d CH 2 + 2KMnO 4 + 4H 2 O → 3HOH 2 C - CH 2 OH + 2MnO 2 + 2KOH
  • Combustion:
  C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O
  • Polymerization (obtaining polyethylene):
  nCH 2 \u003d CH 2 → (-CH 2 -CH 2 -) n
  • Dimerization (V. Sh. Feldblum. Dimerization and disproportionation of olefins. M.: Chemistry, 1978)
  2CH 2 \u003d CH 2 → CH 2 \u003d CH-CH 2 -CH 3

  Biological role

  Ethylene is the first of the discovered gaseous plant hormones, which has a very a wide range biological effects. Ethylene performs in life cycle plants have a variety of functions, including control of seedling development, ripening of fruits (in particular, fruits), blooming of buds (flowering process), aging and falling of leaves and flowers. Ethylene is also called the stress hormone, since it is involved in the response of plants to biotic and abiotic stress, and its synthesis in plant organs is enhanced in response to different kind damage. In addition, being a volatile gaseous substance, ethylene carries out fast communication between different plant organs and between plants in a population, which is important. in particular, with the development of stress resistance.

  Among the best known functions of ethylene is the development of the so-called triple response in etiolated (grown in the dark) seedlings upon treatment with this hormone. The triple response includes three reactions: shortening and thickening of the hypocotyl, shortening of the root, and strengthening of the apical hook (a sharp bend in the upper part of the hypocotyl). The response of seedlings to ethylene is extremely important at the first stages of their development, as it facilitates the penetration of seedlings towards the light.

  In the commercial harvesting of fruits and fruits, special rooms or chambers are used for ripening fruits, into the atmosphere of which ethylene is injected from special catalytic generators that produce gaseous ethylene from liquid ethanol. Usually, to stimulate fruit ripening, the concentration of gaseous ethylene in the atmosphere of the chamber is from 500 to 2000 ppm for 24-48 hours. With more high temperature air and a higher concentration of ethylene in the air, fruit ripening is faster. It is important, however, to ensure control of the carbon dioxide content in the atmosphere of the chamber, since high-temperature ripening (at temperatures above 20 degrees Celsius) or ripening at a high concentration of ethylene in the air of the chamber leads to a sharp increase in the release of carbon dioxide by rapidly ripening fruits, sometimes up to 10%. carbon dioxide in the air after 24 hours from the start of ripening, which can lead to carbon dioxide poisoning of both workers who harvest already ripened fruits, and the fruits themselves.

  Ethylene has been used to stimulate fruit ripening since Ancient Egypt. The ancient Egyptians intentionally scratched or slightly crushed, beat off dates, figs and other fruits in order to stimulate their ripening (tissue damage stimulates the formation of ethylene by plant tissues). The ancient Chinese burned wooden incense sticks or scented candles indoors to stimulate the ripening of peaches (when burning candles or wood, not only carbon dioxide is released, but also incompletely oxidized intermediate combustion products, including ethylene). In 1864 it was discovered that a leak natural gas from street lamps causes inhibition of the growth of nearby plants in length, their twisting, abnormal thickening of stems and roots, and accelerated maturation fruits. In 1901, the Russian scientist Dmitry Nelyubov showed that the active component of natural gas that causes these changes is not its main component, methane, but the ethylene present in it in small quantities. Later in 1917, Sarah Dubt proved that ethylene stimulates premature leaf drop. However, it was not until 1934 that Gein discovered that plants themselves synthesize endogenous ethylene. In 1935, Crocker suggested that ethylene is a plant hormone responsible for the physiological regulation of fruit ripening, as well as for the aging of plant vegetative tissues, leaf drop, and growth inhibition.

  The ethylene biosynthetic cycle begins with the conversion of the amino acid methionine to S-adenosyl methionine (SAMe) by the enzyme methionine adenosyl transferase. Then S-adenosyl-methionine is converted to 1-aminocyclopropane-1-carboxylic acid (ACA, ACC) using the enzyme 1-aminocyclopropane-1-carboxylate synthetase (ACC synthetase). The activity of ACC synthetase limits the rate of the entire cycle; therefore, the regulation of the activity of this enzyme is key in the regulation of ethylene biosynthesis in plants. Last stage The biosynthesis of ethylene requires the presence of oxygen and occurs through the action of the enzyme aminocyclopropane carboxylate oxidase (ACC oxidase), formerly known as the ethylene-forming enzyme. Ethylene biosynthesis in plants is induced by both exogenous and endogenous ethylene (positive Feedback). The activity of ACC synthetase and, accordingly, the formation of ethylene also increases with high levels auxins, especially indoleacetic acid, and cytokinins.

  The ethylene signal in plants is perceived by at least five different families of transmembrane receptors, which are protein dimers. Known, in particular, the ethylene receptor ETR 1 in Arabidopsis ( Arabidopsis). The genes encoding ethylene receptors have been cloned in Arabidopsis and then in tomato. Ethylene receptors are encoded by multiple genes in both Arabidopsis and tomato genomes. Mutations in any of the gene family, which consists of five types of ethylene receptors in Arabidopsis and at least six types of receptors in tomato, can lead to plant insensitivity to ethylene and disruption of the processes of maturation, growth and wilting. DNA sequences characteristic of ethylene receptor genes have also been found in many other plant species. Moreover, ethylene-binding protein has even been found in cyanobacteria.

  Adverse external factors, such as insufficient oxygen content in the atmosphere, flood, drought, frost, mechanical damage (injury) of the plant, attack by pathogenic microorganisms, fungi or insects, can cause increased production of ethylene in plant tissues. So, for example, during a flood, the roots of a plant suffer from an excess of water and a lack of oxygen (hypoxia), which leads to the biosynthesis of 1-aminocyclopropane-1-carboxylic acid in them. ACC is then transported along pathways in the stems up to the leaves and oxidized to ethylene in the leaves. The resulting ethylene promotes epinastic movements, leading to mechanical shaking of water from the leaves, as well as wilting and falling of leaves, flower petals and fruits, which allows the plant to simultaneously get rid of excess water in the body and reduce the need for oxygen by reducing total mass fabrics.

  Small amounts of endogenous ethylene are also formed in animal cells, including humans, during lipid peroxidation. Some endogenous ethylene is then oxidized to ethylene oxide, which has the ability to alkylate DNA and proteins, including hemoglobin (forming a specific adduct with hemoglobin's N-terminal valine, N-hydroxyethyl-valine). Endogenous ethylene oxide can also alkylate the guanine bases of DNA, which leads to the formation of the 7-(2-hydroxyethyl)-guanine adduct, and is one of the reasons for the inherent risk of endogenous carcinogenesis in all living beings. Endogenous ethylene oxide is also a mutagen. On the other hand, there is a hypothesis that if it were not for the formation of small amounts of endogenous ethylene and, accordingly, ethylene oxide in the body, the rate of spontaneous mutations and, accordingly, the rate of evolution would be much lower.

  Notes

  1. DevanneyMichael T. Ethylene (English) . SRI Consulting (September 2009). Archived from the original on August 21, 2011.
  2. Ethylene (English) . WP Report. SRI Consulting (January 2010). Archived from the original on August 21, 2011.
  3. Gas chromatographic measurement of mass concentrations of hydrocarbons: methane, ethane, ethylene, propane, propylene, butane, alpha-butylene, isopentane in the air of the working area. Methodological instructions. MUK 4.1.1306-03  (Approved by the chief state sanitary doctor of the Russian Federation on March 30, 2003)
  4. "Growth and development of plants" V. V. Chub
  5. "Delaying Christmas tree needle loss"
  6. Khomchenko G.P. §16.6. Ethylene and its homologues// Chemistry for applicants to universities. - 2nd ed. - M.: Higher school, 1993. - S. 345. - 447 p. - ISBN 5-06-002965-4.
  7. Lin, Z.; Zhong, S.; Grierson, D. (2009). "Recent advances in ethylene research". J. Exp. bot. 60 (12): 3311-36. DOI:10.1093/jxb/erp204. PMID.
  8. Ethylene and Fruit Ripening / J Plant Growth Regul (2007) 26:143-159 doi:10.1007/s00344-007-9002-y
  9. Lutova L.A. Genetics of plant development / ed. S.G. Inge-Vechtomov. - 2nd ed. - St. Petersburg: N-L, 2010. - S. 432.
  10. . ne-postharvest.com (unavailable link since 06-06-2015 )
  11. Neljubov D. (1901). "Uber die horizontale Nutation der Stengel von Pisum sativum und einiger anderen Pflanzen". Beih Bot Zentralbl. 10 : 128-139.
  12. Doubt, Sarah L. (1917). "The Response of Plants to Illuminating Gas". Botanical Gazette. 63 (3): 209-224.
  
  
  

  Plan:

  Introduction
  
  • 1 Application
  • 2 Electronic and spatial structure of the molecule
  • 3 Basic chemical properties
  Notes
  
  
  

  Introduction

  Ethylene(according to IUPAC: ethene) is an organic chemical compound described by the formula C 2 H 4 . It is the simplest alkene ( olefin). Ethylene is practically not 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. Contains a double bond and therefore refers to unsaturated or unsaturated hydrocarbons. It plays an extremely important role in industry, and is also a phytohormone. Ethylene is the world's most produced organic compound; the total world production of ethylene in 2008 amounted to 113 million tons and continues to grow by 2-3% per year. Drug. Hazard class - the fourth. .

  
  

  1. Application

  Ethylene is the leading product of basic organic synthesis and is used to obtain 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 was used in medicine for anesthesia until the mid-1980s in the USSR and the Middle East. Ethylene is a phytohormone in almost all plants, among other things, it is responsible for the fall of needles in conifers.

  
  

  2. Electronic and spatial structure of the molecule

  The carbon atoms are in the second valence state (sp2 hybridization). As a result, three hybrid clouds are formed on the plane at an angle of 120°, which form three sigma bonds with carbon and two hydrogen atoms. The p-electron, which did not participate in hybridization, forms a bond in the perpendicular plane with the p-electron of the neighboring carbon atom. This forms a double bond between carbon atoms. The molecule has a planar structure.

  
  

  3. 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, less strong, is easily broken, and at the place of the bond breaking, the molecules are joined, oxidized, and polymerized.

  • Halogenation:

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

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

  • Hydrogenation:

  CH 2 \u003d CH 2 + H - H → CH 3 - CH 3 (under the action of Ni)

  • Hydrohalogenation:

  CH 2 \u003d CH 2 + HBr → CH 3 - CH 2 Br

  • Hydration:

  CH 2 \u003d CH 2 + HOH → CH 3 CH 2 OH (under the action of a catalyst)

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

  • 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.

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

  • Combustion:

  C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

  • Polymerization:

  nCH 2 \u003d CH 2 → (-CH 2 -CH 2 -)

  
  

  Notes

  1. DevanneyMichael T. Ethylene - www.sriconsulting.com/CEH/Public/Reports/432.0000/ (English) . SRI Consulting (September 2009).
  2. Ethylene - www.sriconsulting.com/WP/Public/Reports/ethylene/ (English) . WP Report. SRI Consulting (January 2010).
  3. Gas chromatographic measurement of mass concentrations of hydrocarbons: methane, ethane, ethylene, propane, propylene, nbutane, alpha-butylene, isopentane in air working area. Guidelines. MUK 4.1.1306-03 (APPROVED BY THE CHIEF STATE SANITARY PHYSICIAN OF THE RF 30.03.2003) - www.bestpravo.ru/fed2003/data07/tex22892.htm
  4. "GROWTH AND DEVELOPMENT OF PLANTS" V.V. Chub - herba.msu.ru/russian/departments/physiology/spezkursi/chub/index_7.html
  5. "Delaying Christmas tree needle loss" - www.nserc-crsng.gc.ca/Media-Media/ImpactStory-ArticlesPercutant_eng.asp?ID=1052
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  This abstract based on an article from the Russian Wikipedia. Synchronization completed on 07/09/11 21:40:46
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