aromatic hydrocarbons. Benzene and its homologues
Ways to get. one. Obtaining from aliphatic hydrocarbons. To obtain benzene and its homologues in industry, they use aromatization saturated hydrocarbons that are part of the oil. When alkanes with a straight chain consisting of at least six carbon atoms are passed over heated platinum or chromium oxide, dehydrogenation occurs with simultaneous ring closure ( dehydrocyclization). In this case, benzene is obtained from hexane, and toluene is obtained from heptane.
2. Dehydrogenation of cycloalkanes also leads to aromatic hydrocarbons; for this, a pair of cyclohexane and its homologues is passed over heated platinum.
3. Benzene can be obtained from acetylene trimerization, why acetylene is passed over activated carbon at 600 °C.
4. Benzene homologues are obtained from benzene by its interaction with alkyl halides in the presence of aluminum halides (alkylation reaction, or Friedel-Crafts reaction).
5. When fusion salts of aromatic acids with alkali, arenes are released in gaseous form.
Chemical properties. The aromatic nucleus, which has a mobile system of n-electrons, is a convenient object for attack by electrophilic reagents. This is also facilitated by the spatial arrangement of the n-electron cloud on both sides of the flat a-skeleton of the molecule (see Fig. 23.1, b).
For arenes, the most typical reactions proceed according to the mechanism electrophilic substitution, denoted by the symbol S E(from English, substitution, electrophilic).
Mechanism S E can be represented as follows:
At the first stage, the electrophilic particle X is attracted to the n-electron cloud and forms an n-complex with it. Then two of the six n-electrons of the ring form an a-bond between X and one of the carbon atoms. In this case, the aromaticity of the system is violated, since only four n-electrons remain in the ring, distributed among five carbon atoms (a-complex). To preserve aromaticity, the a-complex ejects a proton, and two C-H bond electrons pass into the n-electron system.
The following reactions of aromatic hydrocarbons proceed according to the mechanism of electrophilic substitution.
1. Halogenation. Benzene and its homologues react with chlorine or bromine in the presence of anhydrous A1C1 3 , FeCl 3 , A1Br 3 catalysts.
This reaction produces a mixture from toluene. ortho- and para-isomers (see below). The role of the catalyst is to polarize the neutral halogen molecule with the formation of an electrophilic particle from it.
2. Nitration. Benzene reacts very slowly with concentrated nitric acid, even when heated strongly. However, when acting nitrating mixture(mixtures of concentrated nitric and sulfuric acids), the nitration reaction proceeds quite easily.
3. Sulfonation. The reaction easily passes with "fuming" sulfuric acid (oleum).
- 4. Friedel-Crafts Alkylation- see above methods for obtaining benzene homologues.
- 5. Alkylation with alkenes. These reactions are widely used in industry to produce ethylbenzene and isopropylbenzene (cumene). Alkylation is carried out in the presence of a catalyst A1C1 3 . The reaction mechanism is similar to that of the previous reaction.
All the above reactions proceed according to the mechanism electrophilic substitution S E .
Along with substitution reactions, aromatic hydrocarbons can enter into addition reactions, however, these reactions lead to the destruction of the aromatic system and therefore require large amounts of energy and proceed only under severe conditions.
6. hydrogenation benzene goes under heating and high pressure in the presence of metal catalysts (Ni, Pt, Pd). Benzene is converted to cyclohexane.
Hydrogenation of benzene homologues gives cyclohexane derivatives.
7. Radical halogenation benzene occurs when its vapor interacts with chlorine only under the influence of hard ultraviolet radiation. At the same time, benzene joins three chlorine molecules and forms solid product hexachlorocyclohexane (hexachloran) C 6 H 6 C1 6 (hydrogen atoms are not indicated in the structural formulas).
8. Oxidation by atmospheric oxygen. In terms of resistance to the action of oxidizing agents, benzene resembles alkanes - the reaction requires harsh conditions. For example, the oxidation of benzene with atmospheric oxygen occurs only when its vapor is strongly heated (400 °C) in air in the presence of a V 2 0 5 catalyst; the products are a mixture of maleic acid and its anhydride.
Benzene homologues. The chemical properties of benzene homologues are different from those of benzene, which is due to the mutual influence of the alkyl radical and the benzene ring.
Reactions in the side chain. The chemical properties of alkyl substituents in the benzene ring are similar to alkanes. Hydrogen atoms in them are replaced by halogens by a radical mechanism (S R). That's why in the absence of a catalyst, when heated or UV irradiated, a radical substitution reaction occurs in the side chain. However, the influence of the benzene ring on alkyl substituents leads to the fact that, first of all, the hydrogen at the carbon atom directly bonded to the benzene ring is replaced (and -atom carbon).
Substitution on the benzene ring by mechanism S E Maybe only in the presence of a catalyst(A1C1 3 or FeCl 3). Substitution in the ring occurs in ortho- and para positions to the alkyl radical.
Under the action of potassium permanganate and other strong oxidizing agents on benzene homologues, the side chains are oxidized. No matter how complex the substituent chain is, it is destroyed, with the exception of the a-carbon atom, which is oxidized into a carboxyl group.
Homologues of benzene with one side chain give benzoic acid.
The main sources of production are oil and products of dry distillation (coking) of coal. The separation of aromatic hydrocarbons from coal tar is the oldest and until the 1950s the main method for their production. When heated above 1000 ºС without air access, coal decomposes with the formation of solid (coke), liquid (coal tar, ammonia water) and gaseous (coke oven gases) products of distillation.
Coke– mostly carbon; used in metallurgy.
coking gases- H 2 , CH 4 , CO, CO 2 , N 2 , ethylene hydrocarbons.
Coal tar- contains a large number of organic compounds of various nature. Resin yield about 3%. At the first stage, it is distilled into 4 fractions (Table 11).
Table 11
The main fractions of coal tar
The remainder of the distillation (60%) is called pitch. It is a hard, dark-colored mass that softens when heated.
Individual organic compounds are isolated from the listed fractions by various methods.
In some types of oil, the content of aromatic hydrocarbons reaches 60%. Nevertheless, their main amount is obtained from oil during chemical processing (oil aromatization) - pyrolysis and catalytic reforming, during which dehydrogenation (a) and dehydrocyclization (b) reactions occur:
(a) 
;
cyclohexane benzene
n-hexane benzene
A synthetic method for producing benzene is acetylene trimerization (see Section 5.2.5). Benzene homologues are obtained by alkylation according to the Friedel-Crafts method (Section 6.2.1) or the Wurtz-Fittig method:
bromobenzene butyl bromide butylbenzene
(R. Fittig in 1864 extended the reaction of S. Wurtz to aromatic hydrocarbons for the alkylation and acylation of benzene).
Arenas are extremely versatile.
Benzene, toluene, xylenes are widely used organic solvents and the basis of large-scale organic synthesis - dyes, explosives (TNT), plastics (polystyrene, lavsan), drugs, plant protection products, etc.
Bibliography
1. Nechaev A.P., Eremenko T.V. Organic Chemistry: Proc. for food. in–comrade. - M.: Higher School, 1985. - 463 p.
2. Nechaev A.P. Organic Chemistry: Proc. for avg. specialist. textbook food establishments. specialist. - 2nd ed., revised. and additional - M.: Higher School, 1988. - 318 p.
3. Artemenko A.I. Organic Chemistry: Proc. for building. specialist. universities. - 3rd ed., revised. and additional - M.: Higher school, 1994. - 500 p.
4. Grandberg I.I. Organic Chemistry: Proc. allowance for agricultural universities. - 2nd ed., revised. and additional - M.: Higher School, 1980. - 463 p.
5. Karrer P. Course of organic chemistry. 2nd ed. - L .: Goshimizdat, 1962. - 1216 p.
6. Roberts J., Caserio M. Fundamentals of organic chemistry. - M.: Mir, 1968. - Part 1. - 592 p.; 1968. - Part 2. - 550 p.
7. Kahn R., Dermer O. Introduction to chemical nomenclature. - M.: Chemistry, 1983. - 224 p.
8. Volkov V.A. Vonsky E.V., Kuznetsova G.I. Outstanding Chemists of the World: A Biographical Guide. - M .: Higher school, 1991.
9. Brief chemical encyclopedia. – M.: Sov. Encyclopedia, 1961. - T. 1. - 1262 p.; 1963. - T. 2. - 1086 p.; 1964. - T. 3. - 1112 p.; 1965. - T. 4. - 1182 p.; 1967. - T. 5. - 1184 p.
10. Chmutov K.V. Chromatography. - M.: Chemistry, 1978. - 128 p.
11. Azimov A. The world of carbon. - M.: Chemistry, 1978. - 208 p.
12. Shulpin G.B. This fascinating chemistry. - M.: Chemistry, 1984. - 184 p.
13. Emmanuel N.M., Zaikov G.E. Chemistry and food. – M.: Nauka, 1986. – 173 p.
BUTRENA
Aromatic hydrocarbons (arenes) - cyclic hydrocarbons, united by the concept of aromaticity, which determines common features in the structure and chemical properties.
Classification
According to the number of benzene rings in the molecule, arenas are subdivided on:
mononuclear
multi-core
Nomenclature and isomerism
The structural ancestor of the hydrocarbons of the benzene series is benzene C 6 H 6 from which the systematic names of homologues are built.
For monocyclic compounds, the following non-systematic (trivial) names are retained:
The position of the substituents is indicated by the smallest digits (the direction of the numbering does not matter),
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and for disubstituted compounds, the notation can be used ortho, meta, pair.
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If there are three substituents in the ring, then they should receive the smallest numbers, i.e. the series "1,2,4" takes precedence over "1,3,4".
1,2-dimethyl-4-ethylbenzene (correct) 3,4-dimethyl-1-ethylbenzene (incorrect)
The isomerism of monosubstituted arenes is due to the structure of the carbon skeleton of the substituent; for di- and polysubstituted benzene homologues, more isomerism is added, caused by the different arrangement of substituents in the nucleus.
Isomerism of aromatic hydrocarbons of the composition C 9 H 12:
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Physical properties
The boiling and melting points of arenes are higher than those of alkanes, alkenes, alkynes, they are low-polar, insoluble in water and readily soluble in non-polar organic solvents. Arenas are liquids or solids that have specific odors. Benzenes and many condensed arenes are toxic, some of them exhibit carcinogenic properties. Intermediate products of the oxidation of condensed arenes in the body are epoxides, which either directly cause cancer themselves or are precursors of carcinogens.
Getting arenas
Many aromatic hydrocarbons are of great practical importance and are produced on a large industrial scale. A number of industrial methods are based on the processing of coal and oil.
Oil consists mainly of aliphatic and alicyclic hydrocarbons; for the conversion of aliphatic or acyclic hydrocarbons into aromatic, oil aromatization methods have been developed, the chemical bases of which have been developed by N.D. Zelinsky, B.A. Kazansky.
1. Cyclization and dehydrogenation:
2. Hydrodesmethylation:
3. Benzene homologues are obtained by alkylation or acylation followed by reduction of the carbonyl group.
a) Alkylation according to Friedel-Crafts:
b) Friedel-Crafts acylation:
4. Obtaining biphenyl by the Wurtz-Fitting reaction:
5. Obtaining diphenylmethane by the Friedel-Crafts reaction:
Structure and chemical properties.
Aromaticity Criteria:
Based on theoretical calculations and experimental study of cyclic conjugated systems, it was found that a compound is aromatic if it has:
- Flat cyclic σ-skeleton;
- A conjugated closed π-electron system, covering all atoms of the cycle and containing 4n + 2, where n = 0, 1, 2, 3, etc. This formulation is known as Hückel's rule. Aromaticity criteria make it possible to distinguish conjugated aromatic systems from all others. Benzene contains a sextet of π electrons and follows Hückel's rule at n = 1.
What gives aromaticity:
Despite the high degree of unsaturation, aromatic compounds are resistant to oxidizing agents and temperature, they are more likely to enter into substitution reactions rather than addition. These compounds have increased thermodynamic stability, which is ensured by the high conjugation energy of the aromatic system of the ring (150 kJ/mol); therefore, arenes preferentially enter into substitution reactions, as a result of which they retain aromaticity.
The mechanism of electrophilic substitution reactions in the aromatic ring:
The electron density of the π-conjugated system of the benzene ring is a convenient target for attack by electrophilic reagents.
As a rule, electrophilic reagents are generated during the reaction with the help of catalysts and appropriate conditions.
E - Y → E δ + - Y δ - → E + + Y -
Formation of a π-complex. The initial attack by the electrophile on the π-electron cloud of the ring leads to the coordination of the reactant with the π-system and the formation of a donor-acceptor type complex called π-complex. The aromatic system is not disturbed:
Formation of a σ-complex. The limiting stage, at which the electrophile forms a covalent bond with a carbon atom due to two electrons of the π-system of the ring, which is accompanied by the transition of this carbon atom from sp2- in sp3- hybrid state and disruption of the aromatic, the molecule turns into a carbocation.
Stabilization of the σ-complex. It is carried out by splitting off a proton from the σ-complex with the help of a base. In this case, the closed π-system of the ring is restored due to two electrons of the breaking C – H covalent bond, i.e. the molecule returns to the aromatic state:
Effect of substituents on the reactivity and orientation of electrophilic substitution
Substituents in the benzene ring break the uniformity in the distribution π- electron cloud of the ring and thereby affect the reactivity of the ring.
- Electron donor substituents (D) increase the electron density of the ring and increase the rate of electrophilic substitution, such substituents are called activating.
- Electron-withdrawing substituents (A) lower the electron density of the ring and reduce the reaction rate, called deactivating.
Physical properties
Benzene and its closest homologues are colorless liquids with a specific odor. Aromatic hydrocarbons are lighter than water and do not dissolve in it, but they easily dissolve in organic solvents - alcohol, ether, acetone.
Benzene and its homologues are themselves good solvents for many organic substances. All arenas burn with a smoky flame due to the high carbon content of their molecules.
The physical properties of some arenes are presented in the table.
Table. Physical properties of some arenas
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Name |
Formula |
t°.pl., |
t°.bp., |
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Benzene |
C 6 H 6 |
5,5 |
80,1 |
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Toluene (methylbenzene) |
C 6 H 5 CH 3 |
95,0 |
110,6 |
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Ethylbenzene |
C 6 H 5 C 2 H 5 |
95,0 |
136,2 |
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Xylene (dimethylbenzene) |
C 6 H 4 (CH 3) 2 |
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ortho- |
25,18 |
144,41 |
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meta- |
47,87 |
139,10 |
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pair- |
13,26 |
138,35 |
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Propylbenzene |
C 6 H 5 (CH 2) 2 CH 3 |
99,0 |
159,20 |
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Cumene (isopropylbenzene) |
C 6 H 5 CH(CH 3) 2 |
96,0 |
152,39 |
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Styrene (vinylbenzene) |
C 6 H 5 CH \u003d CH 2 |
30,6 |
145,2 |
Benzene - low-boiling ( tkip= 80.1°C), colorless liquid, insoluble in water
Attention! Benzene - poison, acts on the kidneys, changes the blood formula (with prolonged exposure), can disrupt the structure of chromosomes.
Most aromatic hydrocarbons are life threatening and toxic.
Obtaining arenes (benzene and its homologues)
In the laboratory
1. Fusion of salts of benzoic acid with solid alkalis
C 6 H 5 -COONa + NaOH t → C 6 H 6 + Na 2 CO 3
sodium benzoate
2. Wurtz-Fitting reaction: (here G is halogen)
From 6H 5 -G+2Na + R-G →C 6 H 5 - R + 2 NaG
FROM 6 H 5 -Cl + 2Na + CH 3 -Cl → C 6 H 5 -CH 3 + 2NaCl
In industry
- isolated from oil and coal by fractional distillation, reforming;
- from coal tar and coke oven gas
1. Dehydrocyclization of alkanes with more than 6 carbon atoms:
C 6 H 14 t , kat→C 6 H 6 + 4H 2
2. Trimerization of acetylene(only for benzene) – R. Zelinsky:
3C 2 H2 600°C, Act. coal→C 6 H 6
3. Dehydrogenation cyclohexane and its homologues:
Soviet Academician Nikolai Dmitrievich Zelinsky established that benzene is formed from cyclohexane (dehydrogenation of cycloalkanes
C 6 H 12 t, cat→C 6 H 6 + 3H 2
C 6 H 11 -CH 3 t , kat→C 6 H 5 -CH 3 + 3H 2
methylcyclohexanetoluene
4. Alkylation of benzene(obtaining homologues of benzene) – r Friedel-Crafts.
C 6 H 6 + C 2 H 5 -Cl t, AlCl3→C 6 H 5 -C 2 H 5 + HCl
chloroethane ethylbenzene
Chemical properties of arenes
I. OXIDATION REACTIONS
1. Combustion (smoky flame):
2C 6 H 6 + 15O 2 t→12CO 2 + 6H 2 O + Q
2. Benzene under normal conditions does not decolorize bromine water and an aqueous solution of potassium permanganate
3. Benzene homologues are oxidized by potassium permanganate (discolor potassium permanganate):
A) in an acidic environment to benzoic acid
Under the action of potassium permanganate and other strong oxidants on the homologues of benzene, the side chains are oxidized. No matter how complex the chain of the substituent is, it is destroyed, with the exception of the a -carbon atom, which is oxidized into a carboxyl group.
Homologues of benzene with one side chain give benzoic acid:
Homologues containing two side chains give dibasic acids:
5C 6 H 5 -C 2 H 5 + 12KMnO 4 + 18H 2 SO 4 → 5C 6 H 5 COOH + 5CO 2 + 6K 2 SO 4 + 12MnSO 4 + 28H 2 O
5C 6 H 5 -CH 3 + 6KMnO 4 + 9H 2 SO 4 → 5C 6 H 5 COOH + 3K 2 SO 4 + 6MnSO 4 + 14H 2 O
Simplified :
C 6 H 5 -CH 3 + 3O KMnO4→C 6 H 5 COOH + H 2 O
B) in neutral and slightly alkaline to salts of benzoic acid
C 6 H 5 -CH 3 + 2KMnO 4 → C 6 H 5 COO K + K OH + 2MnO 2 + H 2 O
II. ADDITION REACTIONS (harder than alkenes)
1. Halogenation
C 6 H 6 + 3Cl 2 h ν → C 6 H 6 Cl 6 (hexachlorocyclohexane - hexachloran)
2. Hydrogenation
C 6 H 6 + 3H 2 t , PtorNi→C 6 H 12 (cyclohexane)
3. Polymerization
III. SUBSTITUTION REACTIONS – ionic mechanism (lighter than alkanes)
b) benzene homologues upon irradiation or heating
In terms of chemical properties, alkyl radicals are similar to alkanes. Hydrogen atoms in them are replaced by halogens by a free radical mechanism. Therefore, in the absence of a catalyst, heating or UV irradiation leads to a radical substitution reaction in the side chain. The influence of the benzene ring on alkyl substituents leads to the fact that the hydrogen atom is always replaced at the carbon atom directly bonded to the benzene ring (a-carbon atom).
1) C 6 H 5 -CH 3 + Cl 2 h ν → C 6 H 5 -CH 2 -Cl + HCl
c) benzene homologues in the presence of a catalyst
C 6 H 5 -CH 3 + Cl 2 AlCl 3 → (mixture of orta, pair of derivatives) +HCl
2. Nitration (with nitric acid)
C 6 H 6 + HO-NO 2 t, H2SO4→C 6 H 5 -NO 2 + H 2 O
nitrobenzene - smell almond!
C 6 H 5 -CH 3 + 3HO-NO 2 t, H2SO4→ FROM H 3 -C 6 H 2 (NO 2) 3 + 3H 2 O2,4,6-trinitrotoluene (tol, trotyl)
The use of benzene and its homologues
Benzene C 6 H 6 is a good solvent. Benzene as an additive improves the quality of motor fuel. It serves as a raw material for the production of many aromatic organic compounds - nitrobenzene C 6 H 5 NO 2 (solvent, aniline is obtained from it), chlorobenzene C 6 H 5 Cl, phenol C 6 H 5 OH, styrene, etc.
Toluene C 6 H 5 -CH 3 - a solvent used in the manufacture of dyes, drugs and explosives (trotyl (tol), or 2,4,6-trinitrotoluene TNT).
Xylene C 6 H 4 (CH 3) 2 . Technical xylene is a mixture of three isomers ( ortho-, meta- and pair-xylenes) - is used as a solvent and starting product for the synthesis of many organic compounds.
Isopropylbenzene C 6 H 5 -CH (CH 3) 2 serves to obtain phenol and acetone.
Chlorine derivatives of benzene used for plant protection. Thus, the product of substitution of H atoms in benzene with chlorine atoms is hexachlorobenzene C 6 Cl 6 - a fungicide; it is used for dry seed dressing of wheat and rye against hard smut. The product of the addition of chlorine to benzene is hexachlorocyclohexane (hexachloran) C 6 H 6 Cl 6 - an insecticide; it is used to control harmful insects. These substances refer to pesticides - chemical means of combating microorganisms, plants and animals.
Styrene C 6 H 5 - CH \u003d CH 2 polymerizes very easily, forming polystyrene, and copolymerizing with butadiene - styrene-butadiene rubbers.
VIDEO EXPERIENCES
Benzene is obtained from coal tar formed during the coking of coal, oil, by synthetic methods.
1. Obtaining from aliphatic hydrocarbons. When straight-chain alkanes having at least six carbon atoms per molecule are passed over heated platinum or chromium oxide, dehydrocyclization- formation of an arene with the release of hydrogen: the method of B.A. Kazansky and A.F. Plate
2. Dehydrogenationcycloalkanes (N.D. Zelinsky) The reaction occurs by passing vapors of cyclohexane and its homologues over heated platinum at 3000 0 .
3. Obtaining benzene trimerization of acetylene over activated carbon at 600 0(N.D. Zelinsky )
| 3HC?CH | -- 600?C? |
4. Fusion of salts of aromatic acids with alkali or soda lime:
5. Chemical properties of arenes.
The benzene core has high strength. For arenes, the most typical reactions proceed according to the mechanism electrophilic substitution, denoted by the symbol S E (from the English substitution electrophilic).
Chemical properties of benzene.
1. Substitution reactions:
Halogenation . Benzene does not interact with chlorine or bromine under normal conditions. The reaction can proceed only in the presence of catalysts - anhydrous AlCl 3 , FeCl 3 , AlBr 3 . As a result of the reaction, halogen-substituted arenes are formed:
The role of the catalyst is to polarize the neutral halogen molecule with the formation of an electrophilic particle from it:
Nitration . Benzene reacts very slowly with concentrated nitric acid, even when heated strongly. However, with the so-called nitrating mixture (a mixture of concentrated nitric and sulfuric acids) The nitration reaction proceeds quite easily:
Sulfonation. The reaction easily takes place under the action of “fuming” sulfuric acid (oleum):
2. Friedel-Crafts Alkylation. As a result of the reaction, an alkyl group is introduced into the benzene core to obtain benzene homologues. The reaction proceeds under the action of haloalkanes RCl on benzene in the presence of catalysts - aluminum halides. The role of the catalyst is reduced to the polarization of the RСl molecule with the formation of an electrophilic particle:
Depending on the structure of the radical in the haloalkane, different homologues of benzene can be obtained:
Alkylation with alkenes. These reactions are widely used in industry to produce ethylbenzene and isopropylbenzene (cumene). Alkylation is carried out in the presence of AlCl 3 catalyst. The reaction mechanism is similar to that of the previous reaction:
All the above reactions proceed according to the mechanism electrophilic substitution S E . Addition reactions to arenes lead to the destruction of the aromatic system and require large amounts of energy, so they proceed only under harsh conditions.
3. Addition reactions proceeding with bond breaking:
Hydrogenation. The reaction of hydrogen addition to arenes proceeds under heating and high pressure in the presence of metal catalysts (Ni, Pt, Pd). Benzene is turning to cyclohexane, a benzene homologues - into cyclohexane derivatives:
Radical halogenation. The interaction of benzene vapor with chlorine proceeds according to the radical mechanism only under the influence of hard ultraviolet radiation. In this case, benzene adds three molecules of chlorine and forms solid product - hexachlorocyclohexane (hexachlorane) C 6 H 6 Cl 6:
4. Oxidation by atmospheric oxygen. In terms of resistance to oxidizing agents, benzene resembles alkanes. Only with strong heating (400 ° C) of benzene vapor with atmospheric oxygen in the presence of a V 2 O 5 catalyst, a mixture of maleic acid and its anhydride is obtained:
5. Benzene is on fire. (View experience) The flame of benzene is smoky due to the high carbon content in the molecule.
2 C 6 H 6 + 15 O 2 → 12CO 2 + 6H 2 O
6. The use of arenes.
Benzene and its homologues are used as chemical raw materials for the production of medicines, plastics, dyes, acetone, phenol, and formaldehyde plastics. pesticides and many other organic substances. Widely used as solvents. Benzene as an additive improves the quality of motor fuel. Ethylene is used to produce ethyl alcohol, polyethylene. It accelerates the ripening of fruits (tomatoes, citrus fruits) with the introduction of small amounts of it into the air of greenhouses. Propylene is used for the synthesis of glycerin, alcohol, for the extraction of polypropylene, which is used for the manufacture of ropes, ropes, and packaging material. Based on 1-butene, synthetic rubber is produced.
Acetylene is used for autogenous welding of metals. Polyethylene is used as a packaging material, for the manufacture of bags, toys, household utensils (bottles, buckets, bowls, etc.). Aromatic hydrocarbons are widely used in the production of dyes, plastics, chemical pharmaceuticals, explosives, synthetic fibers, motor fuels, and others. are the products of coal coking. From 1 t kam.-ug. resins can be isolated on average: 3.5 kg benzene, 1.5 kg toluene, 2 kg naphthalene. Of great importance is the production of A. at. from fatty hydrocarbons. For some A. at. purely synthetic methods are of practical importance. Thus, ethylbenzene is produced from benzene and ethylene, the dehydrogenation of which leads to styrene.
TASKS FOR SELF-CONTROL:
1. What compounds are called arenas?
2. What are the characteristic physical properties?
3. A task. From 7.8 g of benzene, 8.61 g of nitrobenzene was obtained. Determine the yield (in%) of the reaction product.
