Answer: Ethylene is the most important representative of a number of non saturated hydrocarbons with one double bond: formula - 
Gas, almost odorless, poorly soluble in water. In air, it burns with a luminous flame. Thanks to the presence
- bonds ethylene easily enters into addition reactions:
(dibromoethane)
(ethyl alcohol) Due to the presence of a double bond, ethylene molecules can combine with each other, forming chains of great length (from many thousands of initial molecules). This reaction is called the polymerization reaction:
Polyethylene is widely used in industry and in everyday life. It is very inactive, does not beat, is well processed. Examples: pipes, containers (barrels, boxes), insulating material, packaging film, glass, toys and much more. Other protozoa unsaturated hydrocarbon is polypropylene:
During its polymerization, polypropylene is formed - a polymer. The polymer is similar in its cumulative properties and application to polyethylene. 
Polypropylene is stronger than polyethylene, so many parts for a variety of machines are made from it, as well as many precision parts, for example, for escalators. Approximately 40% of polypropylene is processed into fibers.
T. 5. pp. 495-496
ETHYLENE (ethene) CH 2 \u003d CH 2, molecular mass 28.05; colorless gas with a slight odor; melting point -169.15°C, boiling point -103.71°C; d -104 4 0.566; t crit 9.2°C, p crit 5.042 MPa; η (liquids) 0.161 mPa s; γ (liquids) 16.4 mN/m; steam pressure (kPa): 4110 (0°C), 2200 (-25°C), 151 (-100°C); Cp 62.16 J/(mol K) (-193°C); ΔH 0 burned -1400 kJ / mol. Solubility (ml in 100 ml solvent at 0°C): water 25.6, ethanol 359; freely soluble in diethyl ether and hydrocarbons.
Ethylene is practically not found in nature. In small quantities, it is formed in the tissues of plants and animals as an intermediate product of metabolism. It has the properties of phytohormones - it slows down growth, accelerates cell aging, ripening and falling of fruits.
According to its chemical properties, it is a typical representative of olefins, it has a high reactivity, especially in electrophilic addition reactions. When ethylene reacts with chlorine, dichloroethane is formed, which, upon dehydrochlorination, turns into vinyl chloride; the latter can be obtained in one stage in the presence of silicon silicide at 450-550°C. Hydration of ethylene leads to ethyl alcohol, hydrohalogenation to ethyl chloride, interaction with SCl 2 or S 2 Cl 2 - to mustard gas S (CH 2 CH 2 Cl) 2, oxidation with oxygen or air in the presence of Ag oxide at 200-300 ° C - to ethylene oxide; liquid-phase oxidation with oxygen in aqueous solutions of PdCl 2 and CuCl 2 at 130°C and 0.3 MPa to acetaldehyde; under the same conditions, vinyl acetate is formed in the presence of CH 3 COOH.
Ethylene is an alkylating agent widely used for benzene alkylation; the reaction is carried out in the gas phase at 400-450°C and a pressure of 1.4 MPa in the presence of AlCl 3 in a stationary layer of diatomaceous earth impregnated with H 3 PO 4 (you can use BF 3 and zeolites).
Ethylene is the initial compound for the production of high and low pressure polyethylene and ethylene oligomers, which are the basis of a number of synthetic lubricating oils. Ethylene-propylene copolymerization on Ziegler-Natta catalysts produces ethylene-propylene rubber with increased resistance to oxidation and abrasion. In industry, copolymers of ethylene with styrene and vinyl acetate are also obtained.
The main method for producing ethylene is the pyrolysis of liquid petroleum distillates or lower paraffinic hydrocarbons. The reaction is usually carried out in tube furnaces at 750-900°C and a pressure of 0.3 MPa. In Russia, Western Europe and Japan, the raw material is straight-run gasoline; the yield of ethylene is about 30% with the simultaneous formation of a significant amount of liquid products, including aromatic hydrocarbons. During the pyrolysis of gas oil, the yield of ethylene is 15-25%. In the USA, the main raw materials are light alkanes (ethane, propane, butane), which is due to their high content in natural gas fields North America; ethylene yield is about 50%.
A method has been developed for producing ethylene from methane: 2CH 4 → C 2 H 4 + H 2 ; the reaction is carried out on the oxides of Mn, Tl, Cd or Pb at 500-900°C in the presence of oxygen. Pyrolysis gases are separated by fractional absorption, deep cooling and distillation under pressure. The purest ethylene is obtained by dehydration of ethanol at 400-450°C over Al 2 O 3 , this method is suitable for laboratory production of ethylene.
Ethylene is used in industrial organic synthesis (in a number of processes it displaces acetylene), as well as a plant growth regulator, to accelerate fruit ripening, plant defoliation and reduce premature fruit drop.
Ethylene is explosive, CPV 3-34% (by volume), flash point 136.1°С, autoignition temperature 540°С, MPC in atmospheric air 3 mg/m 3 in air working area 100 mg/m3.
World production 50 million tons per year (1988).
Lit.: Kirk-Othmer encyclopedia, 3rd ed., v. 9, N. Y., 1980, p. 393-431.
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 combustible 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 relationship is well explained by the difference in strength S-N bonds 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, 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, as 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. 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 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 molecules of other 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. In Western Europe, Russia and Japan, 40-60% of the total amount of the substance is obtained in this way. 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 an 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 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, as insecticide.
The industrial method of obtaining cracking alkan alkan alkan + alken with a longer with a longer carbon carbon carbon carbon carbon carbon with a chain chain with a chain chain example: t = C T = C 10 H 22 C 5 H 12 + C 5 H 10 C 10 H 22 C 5 H 12 + C 5 H 10 decane pentane pentene decane pentane pentene
LABORATORY METHOD OF OBTAINING DEHYDROHALOGENATION REMOVE HYDROGEN HALOGEN ACTION REMOVE HYDROGEN HALOGEN ACTION EXAMPLE: alcoholic alcohol H H solution H H solution H-C-C-H+KOHH 2 C=CH 2 +KCl+H 2 O H Cl ethene H Cl ethene chloroethane (ethylene) chloroethane (ethylene)
POLYMERIZATION REACTION This is the process of combining identical molecules into larger ones. EXAMPLE: n CH 2 \u003d CH 2 (-CH 2 -CH 2 -) n ethylene polyethylene (monomer) (polymer) n - degree of polymerization, shows the number of molecules that have reacted -CH 2 -CH 2 - structural unit
Ethylene application Property Application Example 1. PolymerizationProduction of polyethylene, plastics 2. Halogenation Solvent production 3. Hydrohalogenation For: local anesthesia, solvent production, in agriculture for decontamination of granaries
Property Application Example 4. Hydration Preparation of ethyl alcohol used as a solvent, anti-septic agent in medicine, in the production of synthetic rubber 5. Oxidation with KMnO 4 solution Preparation of antifreeze, brake fluids, in the production of plastics 6. Special property of ethylene: Ethylene accelerates the ripening of fruits
Unsaturated hydrocarbons with 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 the compound depends entirely on structural formula and the type of bonds of its molecule. Chemical properties ethylene is 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
Eten is gaseous substance, with a barely perceptible 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 state of aggregation 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 processing natural gas, as well as 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 homologous series of ethene attach halogen atoms at the site of the break of the pi bond in their molecule. So, an aqueous solution of bromine red-brown 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 through 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 does not have much practical value. However, it shows a genetic link 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
Increasing the temperature, increasing the pressure and using catalysts are the necessary conditions for 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, physical characteristics which depend on the value of n - the degree of polymerization. If it is small, then the substance is in liquid state of aggregation. If the indicator approaches 1000 links, then such a polymer is used to make polyethylene film, flexible hoses. If the degree of polymerization exceeds 1500 links in the chain, then the material is a solid white color 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 abrasion resistance is used in the manufacture of automotive engine lubricants, while its low toxicity and tissue tolerance human body allowed the use of Teflon prostheses in surgery.
In our article, we considered such chemical properties of olefins as ethylene combustion, addition reactions, oxidation and polymerization.