Electrophilic substitution in the benzene ring. Method for obtaining ethylbenzene How poisoning occurs
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Technology of joint production of styrene and propylene oxide
The general technological scheme for the joint production of styrene and propylene oxide is shown in fig. 3. In this technology, the oxidation of ethylbenzene is carried out in a tray column 1. In this case, both heated ethylbenzene and air are fed to the bottom of the column. The column is equipped with coils located on the plates. Heat is removed by water supplied to these coils. If a catalyst is used to intensify the process, then the process must be carried out in a series of bubbling reactors connected in series, into which ethylbenzene charge (a mixture of fresh and return ethylbenzene with a catalyst solution) is fed countercurrently to air. In this case, the oxidation products pass sequentially through the reactors, each of which is supplied with air.
The gas-vapor mixture from the upper part of the reactor enters condenser 2, in which the entrained ethylbenzene, as well as impurities of benzoic and formic acids, are mainly condensed. After separating the condensate from the cans, it is sent to the scrubber 4 for acid neutralization with alkali. After neutralization, ethylbenzene is returned to reactor C 1. Ethylbenzene is also fed there from column 10. Gases are removed from the system. The oxidate from the bottom of column 1, containing about 10% hydroperoxide, is sent to distillation column 3 for concentration. The hydroperoxide concentration is carried out under high vacuum. Despite the high energy costs, this process is best carried out on a double distillation unit. At the same time, part of the ethylbenzene is distilled off in the first column at a lower vacuum, and the rest of the ethylbenzene with impurities is distilled off in the second column at a deeper vacuum. The distillate of this column is returned to the first column, and concentrated (up to 90%) hydroperoxide is obtained in the cube, which is sent for epoxidation. The oxidate is preliminarily cooled in the heat exchanger 5 by the initial ethylbenzene.
Rice. four. Technological scheme of joint production of styrene and propylene oxide; 1 - oxidation column; 2 - capacitor; 3.7-10.18 - distillation columns; 4 - alkaline scrubber; 5,12,14 - heat exchangers; 6 - epoxidation column; 11 - mixing evaporator; 13.15 - dehydration reactors; 16 - refrigerator; 17 - Florentine vessel; I - air; II - ethylbenzene; III - propylene; IV - alkali solution; V - gases; VI - catalyst solution; VII - propylene oxide; VIII - resins; IX - water layer; X - styrene; XI - for dehydrogenation; XII-steam
In column 3, ethylbenzene with acid impurities is distilled off, so the upper product is also sent to scrubber 4. From the bottom of column 3, concentrated hydroperoxide enters the epoxidation column 6. (Epoxidation can also be carried out in a cascade of reactors.) A catalyst solution from cube of column 9. Fresh catalyst is also fed there. Fresh and return (from column 7) propylene is also fed to the bottom of the column. The reaction products, together with the catalyst solution, are withdrawn from the top of the column and sent to distillation column 7 for distillation of propylene. The gases are removed from the top of the column and from the system for disposal or incineration. The bottom product of column 7 enters the distillation column 8 to isolate product propylene oxide as a distillate. The bottom liquid of column # enters column 9 to separate the synthesis products from the catalyst solution.
The catalyst solution from the bottom of the column is returned to the epoxidation column 6, and the top product enters the Yull distillation column for separating ethylbenzene from methylphenylcarbinol and acetophenone. A mixture of methylphenylcarbinol (MPC) and acetophenone is fed into evaporator 11, in which methylphenylcarbinol and acetophenone are evaporated and separated from the resins using superheated steam. The vapor mixture, overheated to 300°C, enters reactor 13 for dehydration of methylphenylcarbinol. This reactor is partially dehydrated. Since the dehydration reaction is endothermic, before the dehydration products enter the other reactor (reactor 15), the dehydration products are superheated in the heat exchanger 14.
The conversion of methylphenylcarbinol after two reactors reaches 90%. The dehydration products are cooled with water in the refrigerator 76 and enter the Florentine vessel 17, in which the organic layer is separated from the water. The upper hydrocarbon layer enters the distillation column 18 to separate styrene from acetophenone. Acetophenone is then hydrogenated in a separate unit to methylphenylcarbinol, which is fed to the dehydration section.
The selectivity of the process for propylene oxide is 95–97%, and the yield of styrene reaches 90% for ethylbenzene. In this case, 2.6-2.7 tons of styrene is obtained from 1 ton of propylene oxide.
Thus, the considered technology is a complex system that includes many recycles for ethylbenzene, propylene, and a catalyst. These recycles lead, on the one hand, to an increase in energy costs, and on the other hand, they allow the process to be carried out under safe conditions (at a low concentration of hydroperoxide - 10--13%) and achieve complete conversion of the reagents: ethylbenzene and propylene.
Consequently, this process needs to be optimized. The proposed technological scheme makes full use of the heat of reactions and flows. However, instead of the refrigerator 16, it is better to use a waste heat boiler, in which low-pressure steam can be produced. To do this, it is necessary to supply water condensate to the waste heat boiler, from which steam will be obtained. In addition, it is necessary to provide for a more complete use of exhaust gases and tar, an alkaline salt solution from scrubber 4, as well as additional purification of the water layer of the Florentine vessel. The most significant improvement of the technological scheme can be the replacement of dehydration reactors with a column in which a combined reaction-rectification process can be organized. This process takes place on an ion-exchange catalyst in the vapor-liquid version, i.e., at the boiling temperature of the mixtures passing through the column, and can be represented by a diagram (Fig. 5).
Rice. 5.
In this version of the process, the conversion and selectivity can reach 100%, since the process proceeds at low temperatures and a short residence time of the synthesis products in the reactor. heteroazeotrope with water (boiling point below 100 °C), which makes it possible to exclude its thermopolymerization.
1-4 - distillation columns; I – hydrocarbon condensate; II - ethylbenzene for recycling to the reactor subsystem; III - benzene-toluene fraction; IV - styrene; V - resins.
In a distillation column 1 the main amount of ethylbenzene is separated along with benzene and toluene.
in a column 3 all ethylbenzene and part of styrene are distilled off as a distillate. This fraction is returned as food to the column 1. So the columns 1-3 work as a three-column complex.
The final purification of styrene from resins is carried out in a column 4 (often a distillation cube is used for this). All columns in which styrene is present operate under high vacuum so that the bottom temperature does not exceed 100 °C.
Let us consider some features of the above technological separation scheme. In such a production scheme, a variant is usually used in which the second predetermined separation is carried out in the first stage. Namely, benzene and toluene are distilled off together with ethylbenzene in the first column, and then volatile components are distilled off from ethylbenzene. In terms of energy costs, this option is less profitable. However, given the reactivity of styrene (high activity and ability to thermopolymerize), this option is more preferable. Especially if we take into account the low content of benzene and toluene in the reaction mixture.
Given the high reactivity of styrene, “double rectification” is usually used to separate the “ethylbenzene-styrene” pair, which makes it possible to reduce the hydraulic resistance of the distillation columns, and, consequently, the temperature in the stills, which should not exceed 100 °C (with the necessary vacuum). It is at this temperature that the thermopolymerization of styrene begins.
In general, any "double rectification" is unacceptable both in terms of energy and capital costs. The use of this option is a necessary measure. In this case, two options for “double rectification” are possible (Fig. 3.4, a,b).
Technological design of "double" rectification:
a- option I; b- option II; 1-2 - distillation columns; I – mixture of ethylbenzene and styrene; II - styrene and polymers; III - ethylbenzene.
In the first version, in the first column, along with the complete distillation of ethylbenzene (or a highly volatile component for any other system), part of the styrene is distilled off. In this case, the ratio between ethylbenzene and styrene in the distillate of the first column is chosen so that the bottom liquid of column 2 in its composition approximately corresponds to the composition of the initial mixture of the column 1.
In the second version in the column 1 pure ethylbenzene is distilled off. In the cube of this column, such an amount of ethylbenzene remains that it allows, under an acceptable vacuum, to maintain a temperature of no more than 100 ° C.
in a column 2 as a distillate, the remaining ethylbenzene is distilled off together with styrene, the amount of which is determined by the ratio of ethylbenzene and styrene in the initial mixture of the first column.
In the case of separation of ethylbenzene and styrene, preference may be given to the first option of "double distillation", in which the column 2 only part of the styrene is heated, while in the second variant all styrene is heated in the bottoms of both columns, and this, even under vacuum, leads to its loss due to thermopolymerization. True, a large difference in energy costs can compensate for the loss of styrene, but this requires a more detailed comparison.
To solve the problem of separating the pair "ethylbenzene - styrene", a variant with one column filled with packing with low hydraulic resistance can be proposed. In this case, given the large phlegm flows, there will be different quantities liquid and steam flows along the height of the column. Therefore, for stable operation of the packed column, different diameters of the upper and lower parts of the column are required. Such a column makes it possible to separate this pair of components at a temperature in the cube of the column not higher than 100 °C.
Packed column with strengthening and exhausting parts of different diameters:
I – mixture of ethylbenzene and styrene; II - styrene and polymers; III - ethylbenzene.
Principles in the technology of obtaining styrene by dehydrogenation of ethylbenzene.
· Technology of production of styrene by dehydrogenation of ethylbenzene refers to one-stage chemical processes.
· Available ethylbenzene obtained by alkylation of benzene with olefins is used as a feedstock.
Technological solutions used in industry with the introduction of steam between two or three layers of catalyst, the use of heat exchangers built into the reactor, as well as
· An efficient catalytic system makes it possible, at a sufficiently high selectivity of about 90%, to achieve the conversion of ethylbenzene in one pass at the level of 60-75%.
· The benzene recirculation flow connecting the separation and reactor subsystems of the technology ensures the complete conversion of the feedstock.
Reduced energy costs on the dehydrogenation process can be achieved not only through efficient heat exchange between the incoming and outgoing streams, but also through the use of instead of water vapor(energy carrier and diluent) inert gas. In this case, heat must be supplied between the catalyst beds using built-in heat exchangers. Replacing steam with an inert gas (nitrogen, CO 2) avoids multiple evaporation and condensation of water, which has a high latent heat of evaporation. In this case, the cost of cleaning the water condensate contaminated with aromatic compounds is also reduced, and in general, the consumption of water by production will decrease.
Important integral part technology advocates separation subsystem. In this case, as noted earlier, a significant factor influencing the overall performance of the technology is the modes of distillation separation. They must provide conditions under which there is no thermopolymerization of styrene. It is energetically most expedient to use one packed column with low hydraulic resistance instead of double distillation, or a scheme of heteroazeotropic distillation complexes.
Finally, heterogeneous catalytic nature of the process allows you to simply create devices and technological lines of large unit capacity.
Characteristics of distillation residues of styrene rectification and ways of their processing.
Petrochemical processes are the most complex of chemical industries, since the production of many monomers is associated with the formation of a large amount of secondary and by-products, waste. The economic efficiency of production largely depends on the methods of waste disposal.
There are two main methods used for this: fuel and chemical. The advantage of the second method is undeniable, since the issue of raw materials is rationally solved, since many production wastes contain a number of valuable monomers and organic compounds. Incineration, on the contrary, causes air pollution, corrosion of equipment, and is lost in huge quantities secondary material resources.
During the isolation and purification of styrene in the process of distillation, distillation residues accumulate, the utilization of which is extremely important. Their composition includes a large number of different organic compounds, including monomeric styrene, the complete extraction of which in distillation columns is not achieved.
Depending on the conditions of fractionation of furnace oil, the content of styrene in the distillation residue of distillation may vary from 10 to 50%, and polystyrene - 15-70 %.
Implementation in last years highly effective inhibitors of the thermal polymerization of styrene in the process of its production made it possible to significantly reduce the amount of residual styrene and polystyrene in KORS. This led to the fact that the synthesis of the film-forming agent became unpromising and the main way of utilization of KORS was its use as an additive to boiler fuel. The issue of disposal of KORS has been dealt with for more than a dozen years, but it still remains relevant.
Distillation residues of styrene rectification by composition can be conditionally represented by three groups of substances
Monomers
Polymers and
Products of organic synthesis.
As a result of the research, about 95% of the substances that make up the KORS were identified.
Depending on the styrene production methods, the reactor operating mode, the catalyst service life, the operating mode of the distillation columns, the inhibiting system used, and the residence time in the strippers, the composition of the KORS varies quite widely.
The main components that make up KORS formed during the production of styrene by dehydrogenation of ethylbenzene include: styrene, methylstyrenes, ethylbenzene, polystyrene, divinylbenzene, naphthalene, diphenyl, unidentified "light" substances, high-boiling "heavy" residue, etc.
Based on the components of the KORS composition, the following ways of its processing can be proposed:
1) division of KORS into factions with their further full or partial use.
2) isolation of the polymer part from KORS associated mainly with the purpose of using a styrene polymer as a basis for obtaining film-forming compositions.
Polymer isolation was proposed by two methods: distillation of volatile components and extraction. It should be noted that molecular mass polystyrene in VAT residues varies over a fairly wide range from 1000 to 110000, so attempts to isolate and use polystyrene present significant difficulties.
3) direct disposal of KORS with obtaining a valuable product for its further application.
Direct disposal of KORS - two directions are considered along this path:
The use of KORS as a plasticizer and
To obtain film-forming materials.
A number of works are aimed at the use of KORS in road construction as a component of asphalt-bitumen coatings, which improves adhesion to gravel and adhesion to the ground. However, given use KORS is futile. This is primarily due to its toxicity. Monomeric styrene is present in KORS in much larger quantities than is permissible by sanitary standards. Therefore, most studies have aimed to utilize KORS in such a way as to reduce the content of monomeric styrene in the resulting product using polymerization.
4) neutralization of KORS, as a rule, combustion in the form of a solution - liquid fuel.
The process of neutralization of KORS is determined by its toxicity - mainly by the residual styrene contained in it, as well as by the presence of a very toxic and hazardous to human health carcinogen product - 3,4-benz (a) pyrene (up to 3000 mg / kg). The classical method of neutralization - the burning of KORS in special furnaces is difficult because the content of the polymer in it varies. As a result, a large amount of soot is formed during combustion, containing up to 120,000 µg/kg of 3,4-benz(a)pyrene. When burning KORS containing sulfur as an inhibitor, a large amount of sulfur dioxide is formed, which also requires capture or neutralization.
5) More technologically advanced combustion of KORS in toluene solution or another solvent, such as polyalkylbenzene resins. This method is used by most factories producing styrene.
At OAO Angarsknefteorgsintez, for example, KORS was used as a fuel for the combustion of chemically contaminated water in thermal furnaces mixed with coal-fired fuel oil, at OAO Nizhnekamskneftekhim, a liquid waste disposal unit was launched and mastered.
a) Halogenation. Electrophilic substitution reactions take place in the presence of catalysts - chlorides or bromides of aluminum or iron.
Halogenation of benzene homologues usually results in a mixture of isomers, since alkyl substituents are orientants of the first kind. In general, the process is shown in the diagram:
b ) Nitration. Benzene and its homologues form nitro derivatives quite easily if not pure Nitric acid, and the so-called nitrating mixture - concentrated HNO 3 and H 2 SO 4:
nitrobenzene
trinitrotoluene
in) Alkylation. As mentioned above, Friedel-Crafts alkylation is one of the main laboratory methods for obtaining benzene homologues:
In industry, alkylation with alkenes is widely used. The role of the catalyst in this case is played by the hydrogen ion H+. No products other than benzene homologues are formed. When alkylated with ethene (ethylene), ethylbenzene is obtained, and in the case of propene (propylene), isopropylbenzene (cumene) is formed
2 . catalytic hydrogenation benzene and its homologues occurs at elevated pressure using catalysts (Ni, Pt). In this case, benzene is hydrogenated to cyclohexane, and, for example, methylbenzene (toluene) to methylcyclohexane.
C 6 H 5 CH 3 + 3H 2 C 6 H 11 CH 3
3. Radical reactions proceed during the interaction of arene vapors under harsh conditions (UV radiation or temperatures of the order of 500 ° C). It should be noted that benzene and its homologues react differently.
In the case of benzene, radical attachment
During the radical chlorination of toluene, hydrogen atoms will be successively replaced by the mechanism radical substitution.
4. Oxidation. Oxidation is more characteristic of benzene homologues. If the homologue had only one side chain, then the organic oxidation product would be benzoic acid. In this case, the length and structure of the chain do not matter. During oxidation with potassium permanganate in an acidic medium, homologues following toluene, in addition to benzoic acid, carbonic acid is formed.
Some properties of styrene.
As mentioned above, styrene does not belong to arenas, since it has double bond, and the main type chemical reactions for it there will be addition, oxidation and polymerization reactions.
So styrene easily reacts with bromine water, discoloring it, which is a qualitative reaction to a double bond:
According to the same scheme, hydrogenation of styrene occurs on a nickel catalyst:
The oxidation of styrene is carried out with a cold aqueous solution of potassium permanganate, the oxidation product will be an aromatic dihydric alcohol:
When oxidized with a hot solution of potassium permanganate in the presence of sulfuric acid, benzoic acid and carbon dioxide will be formed.
An important reaction of great practical importance is the styrene polymerization reaction:
The vinyl group is a type I orientant; therefore, further catalytic substitution (for example, with haloalkanes) will go to the ortho and para positions.
7.3.Examples of problem solving
Example 21. The ozone density of a gas mixture consisting of benzene and hydrogen vapor is 0.2. After passing through the contact apparatus for the synthesis of cyclohexane, the value of this relative density was 0.25. Determine the volume fraction of cyclohexane vapor in the final mixture and the practical yield of cyclohexane.
Solution:
1) Find the molar mass of the initial mixture:
M cm \u003d D (O 3) ∙ M (O 3) \u003d 0.2 ∙ 48 \u003d 9.6 g / mol.
2) The molar mass of the final mixture is 0.25 ∙ 48=12 g/mol.
3) Find the molar ratio of the components in the initial mixture
M cm \u003d φ ∙ M (benz.) + M (hydrogen.) ∙ (1-φ), where φ-molar (volume) fraction of benzene
9.6 \u003d 78φ + 2 (1 - φ); 7.6 = 76φ; φ=0.1.
Hence, the volume fraction of hydrogen is 0.9.
Therefore, hydrogen is in excess, we calculate for benzene.
4) Let the amount of the initial mixture be 1 mol.
Then n(C 6 H 6) = 0.1 mol, n(H 2) = 0.9 mol,
and the mass of the initial mixture m cm \u003d 1 ∙ 9.6 \u003d 9.6 g.
Let us denote the amount of reacted benzene –z(mol) and
Let's make a quantitative balance of this reaction.
C 6 H 6 + 3H 2 \u003d C 6 H 12
Was 0.1 0.9 0
Reacted z 3 z z
We write this data for convenience in the form of a table:
5) Find the total amount of substances in the final reaction mixture:
n(kon) \u003d 0.1 - z + 0.9 - 3z + z \u003d 1 - 3 z.
Since the total mass of substances in the contact apparatus has not changed,
then n (con) \u003d m cm / M (final) \u003d 9.6 / 12 \u003d 0.8 mol.
6) Then 1 – 3z = 0.8; 3z = 0.2; z=0.067.
In this case, the volume fraction of cyclohexane is 0.067/0.8 = 0.084.
7) The theoretical amount of cyclohexane is 0.1 mol; the amount of cyclohexane formed is 0.067 mol. practical way out
η = 0.067/0.1= 0.67 (67.0%).
Answer: φ(cyclohexane) = 0.084. η = 0.067/0.1= 0.67 (67.0%).
Example 22. The neutralization of a mixture of aromatic acids obtained by oxidation of a mixture of ethylbenzene and its isomers requires a volume of sodium hydroxide solution five times smaller than the minimum volume of the same solution required to absorb all carbon dioxide obtained by burning the same portion of the mixture of isomers. Determine the mass fraction of ethylbenzene in the initial mixture.
Solution:
1) Ethylbenzene - C 6 H 5 C 2 H 5. M = 106 g / mol; its isomers are dimethylbenzenes having the same molecular formula C 6 H 4 (CH 3) 2 and the same molar mass as ethylbenzene.
Let the amount of ethylbenzene be x(mol) and the amount of dimethylbenzene mixture be y(mol).
2) Let's write the equations for the oxidation reactions of ethylbenzene and its isomers:
5C 6 H 5 C 2 H 5 + 12KMnO 4 + 18H 2 SO 4 5C 6 H 5 COOH + 5CO 2 +
5C 6 H 4 (CH 3) 2 + 12KMnO 4 + 18H 2 SO 4 5C 6 H 4 (COOH) 2 +
12MnSO 4 + 6K 2 SO 4 + 28H 2 O
Obviously, the amounts of benzoic acid and the mixture of phthalic acids are also x and y, respectively.
3) Neutralization equations for the obtained organic acids:
C 6 H 5 COOH + NaOH \u003d C 6 H 5 COOHa + H 2 O
C 6 H 4 (COOH) 2 + 2NaOH \u003d C 6 H 4 (COOHa) 2 + 2 H 2 O
It follows from these equations that the total amount of alkali used for
neutralization of a mixture of acids n(total) = x + 2 y
4) Consider the hydrocarbon combustion equations, given that they all
have the molecular formula C 8 H 10 .
C 6 H 5 C 2 H 5 + 10.5 O 2 8 CO 2 + 5H 2 O
C 6 H 4 (CH 3) 2 + 10.5 O 2 8 CO 2 + 5H 2 O
5) From these equations it follows that the total amount of carbon dioxide after combustion of the initial mixture of arenes is n(CO 2) = 8x + 8y
6) Since a minimum amount of alkali is required, neutralization proceeds with the formation of an acid salt:
NaOH + CO 2 \u003d NaHCO 3
Thus, the amount of alkali to neutralize CO 2 is also equal to
8x + 8y. In this case, 8x + 8y = 5(x + 2y); y=1.5x. x =2/3y 7) Calculation of the mass fraction of ethylbenzene
ω(ethylbenzene) = m(ethylbenzene)/m(total) = 106x/(106x +106y) =
1/ (1 +1,5) = 0,4 .
Answer: ω (ethylbenzene) \u003d 0.4 \u003d 40%.
Example 23. A mixture of toluene and styrene was burned in excess air. When passing the products of combustion through an excess of lime water, 220 g of sediment was formed. Find the mass fractions of the components in the original mixture, if it is known that it can attach
2.24 L HBr (n.a.).
Solution:
1) Only styrene reacts with hydrogen bromide in a ratio of 1:1.
C 8 H 8 + HBr = C 8 H 9 Br
2) The amount of hydrogen bromide substance
n(HBr) \u003d n (C 8 H 8) \u003d 2.24 / 22.4 \u003d 0.1 mol.
3) Let's write the reaction equation for the combustion of styrene:
C 8 H 8 + 10 O 2 8 CO 2 + 4H 2 O
In accordance with the reaction equation, when 0.1 mol of styrene is burned, 0.8 mol of carbon dioxide is formed.
4) Carbon dioxide reacts with an excess of calcium hydroxide also in
molar ratio 1:1 with the formation of a precipitate of calcium carbonate:
Ca(OH) 2 + CO 2 = CaCO 3
5) The total amount of calcium carbonate is
n (CaCO 3) \u003d m (CaCO 3) / M (CaCO 3) \u003d 220/100 \u003d 2.2 mol.
This means that during the combustion of hydrocarbons, 2.2 mol CO 2 was also formed, from
which 0.8 mol gives styrene during combustion.
Then the share of toluene accounts for 2.2 - 0.8 \u003d 1.4 mol of CO 2.
6) Toluene combustion equation:
C 7 H 8 + 9 O 2 7CO 2 + 4H 2 O
The amount of toluene is 7 times less than the amount of carbon dioxide:
n(toluene) = 1.4/7 = 0.2 mol.
7) Mass of styrene m(styrene) = n(styrene)∙M(styrene) = 0.1∙104 =10.4(g);
mass of toluene m(thol) = n(thol)∙M(tol) = 0.2∙92 = 18.4(g).
8) The total mass of the mixture of hydrocarbons is 10.4 + 18.4 = 28.8 (g).
mass fraction styrene: ω = 10.4/ 28.8 = 0.361;
mass fraction of toluene ω=0.639.
Answer: ω (styrene) \u003d 0.361 \u003d 36.1%; ω(toluene)=0.639=63.9%.
7.4. Tasks and exercises for independent solution
189 . Draw the graphical formulas of all arene isomers with the general formula C 9 H 12. Name these compounds.
190 . Get a) meta-nitrotoluene from methane, b) styrene from ethane, c) benzyl alcohol from n-heptane, using any inorganic substances and catalysts
191. Identify the following compounds: a) benzene, styrene, toluene; b) hexene, cyclohexane, toluene; c) ethylbenzene, styrene, phenol.
192. Carry out a chain of transformations:
coke HCl Cact CH 3 Cl Cl 2.
a) CaCO 3 A B C D E
1000 o 500 o FeCl 3 UV
NaOH C 2 H 4 Br 2 KOH KMnO 4
b) sodium benzoate A B C D E
alloyed H + UV alcohol H 2 O
t KMnO 4 C 2 H 5 Cl Cl 2 KOH
c) n-heptane A B C D E
Cr 2 O 3 H + AlCl 3 UV H 2 O
193 . Hydrocarbon C 9 H 12 reacted with bromine when heated. As a result, a compound of composition C 9 H 5 Br 7 was obtained. Write the structural formulas of all hydrocarbons that could give such a result. Justify the answer.
194. Draw the structural formula of the nearest styrene homologue having cis- and trans-isomers. Specify the types of hybridization of carbon atoms in this compound.
195. In which of the following substances do all carbon atoms have sp 2 - hybridization: toluene, butadiene 1,3, cyclohexane, ethylbenzene, styrene, benzene?
196. Get ethylbenzene from ethanol without using other organic reagents. You can use any inorganic substances and catalysts.
197. Give the sequence of reactions that can be used to obtain isophthalic acid (1,3 benzenedicarboxylic acid) from cumene.
198. a) How many isomers does an arene have, the molecule of which contains 58 protons. Draw and name these isomers.
b) Does it have isomers of arenes, the molecule of which contains 50 electrons? Justify your answer
199. The cyclotrimerization of acetylene at 500°C produced a gas mixture with an air density of 2.24. Calculate the practical yield of benzene.
200. As a result of the cyclotrimerization of acetylene at 500°C and a pressure of 1013 kPa, after cooling, 177.27 ml of a liquid with a density of 0.88 g/ml were obtained. Determine the amount of acetylene consumed under the synthesis conditions if the practical yield was 60%.
201 . During catalytic dehydrocyclization, 80 g of n-heptane were released
67.2 liters of hydrogen (N.O.). Calculate the practical yield of the product obtained.
202. Hydrocarbon decolorizes bromine water, under the action of an acidified solution of KMnO 4 forms benzoic acid with the release of carbon dioxide. When treated with an excess of ammonia solution of silver oxide, a white precipitate is observed. At room temperature, the initial hydrocarbon is liquid, and the mass fraction of hydrogen in it is 6.9%. Define a hydrocarbon.
203. A mixture of benzene and cyclohexene with a molar fraction of benzene of 80% decolorizes 200 g of a 16% solution of bromine in carbon tetrachloride. What mass of water is formed when the same mass of the mixture is burned in oxygen?
204. In the reaction of benzene nitration with an excess of the nitrating mixture, 24.6 g of nitrobenzene was obtained. What volume of benzene (density 0.88 g/ml) reacted?
205 . During the nitration of one of the arenes with a mass of 31.8 g, only one nitro derivative with a mass of 45.3 g was formed. Determine the formula of the arene and the nitration product.
206 . A mixture of benzene and cyclohexane weighing 5 g reacted with bromine (in the dark and without heating) in the presence of iron (III) bromide. The volume of released hydrogen bromide was 1.12 l (n.a.). Determine the composition of the mixture in mass fractions.
207. Calculate the mass of bromobenzene obtained by reacting 62.4 g of benzene with 51.61 ml of bromine with a density of 3.1 g/ml in the presence of iron(III) bromide, if the yield is 90% of theoretical.
208 . During catalytic bromination of 50 ml of toluene (density 0.867 g/ml) with a yield of 75%, a mixture of two monobromo derivatives and a gas was obtained, which was passed through 70 g of a 40% solution of butene-1 in benzene. Find the mass fractions of substances in the resulting solution.
209. As a result of bromination of 46 g of toluene in the light, a mixture of mono- and dibromo derivatives was obtained. The volume of gas released was 17.92 L (N.O.) What is the volume of 10% sodium carbonate solution
(density 1.1 g / ml) reacted with the evolved gas if the molar concentrations of the acid salt and hydrogen bromide are equal in the resulting solution.
210. The gas released during the production of bromobenzene from 44.34 ml of benzene (density 0.88 g/ml) reacted with 8.96 l(N.O.) of isobutylene. The yield of bromobenzene was 80% of theoretical, and the reaction with isobutylene took place in 100% yield. What compounds were formed in this case? Calculate their masses.
211. What volume of a 10% sodium hydroxide solution with a density of 1.1 g / ml will be required to neutralize the gas released during the production of bromobenzene from 31.2 g of benzene?
212 . When burning 5.2 g of some hydrocarbon in excess of oxygen, 8.96 liters of carbon dioxide (n.c.) are formed. Determine the true formula of a substance if the relative density of its vapor in terms of helium is 26.
213 . A mixture of styrene and ethylcyclohexane capable of reacting with 4.48 liters of hydrogen chloride (N.O.) was burned. This formed 134.4 g of a mixture of water and carbon dioxide. Find the volume of oxygen required to burn the same portion of the mixture.
214 . The mass of the mixture of toluene and styrene is 29.23 times greater than the mass of hydrogen required for the complete catalytic hydrogenation of the initial mixture. Find the quantitative ratio of the components of the mixture.
215 . A mixture of benzene, toluene and ethylbenzene weighing 13.45 g was oxidized with potassium permanganate in an acid medium. This produced 12.2 g of benzoic acid and 1.12 L (N.O.) of carbon dioxide. Find the mass fractions of hydrocarbons in the original mixture.
216. When burning 23.7 g of a mixture of benzene and ethylbenzene, the volume of oxygen consumed was 1.2917 times greater than the total volume of carbon dioxide. Determine the mass fractions of substances in the initial mixture, as well as the mass of the precipitate that forms when the combustion products are passed through an excess of lime water solution.
217. During the oxidation of 26.5 g of 1,4-dimethylbenzene with a hot neutral solution of potassium permanganate, 66.55 g of a precipitate fell out. Determine what part of the starting material is oxidized.
218. Ethylbenzene, weighing 42.4 g, was treated first with an excess of an acidified potassium permanganate solution, and then with an even greater excess of a KOH solution. The water was then evaporated and the dry residue was calcined. After condensation of the vapors, 26.59 ml of a colorless liquid with a density of 0.88 g/ml were obtained. Determine the practical yield of the product.
219. A mixture of styrene and dimethylcyclohexane capable of discoloring 320 g of 5% bromine water was burned in air. This formed 67.2 g of a mixture of water and carbon dioxide. Calculate the volume of air consumed for combustion if the volume fraction of oxygen is 20%.
220. In one of the arenes, the mass fraction of neutrons is 54.717%. Identify the arene, draw and name its isomers.
221. Determine the true formula of a hydrocarbon if the mass of one of its molecules is 17.276. 10 -23 g, and the mass fraction of hydrogen is 7.69%.
222. The relative density of hydrocarbon vapors in neon is 6. It is known that the hydrocarbon does not react with bromine water, it is oxidized by an acidified solution of potassium permanganate to terephthalic (1,4-benzenedicarboxylic) acid, and the number of carbon atoms is 75% of the number of hydrogen atoms. Define a hydrocarbon.
223. What mass of toluene is required to obtain 113.5 g of trinitrotoluene if the product yield is 82% of theoretical?
224. What volume of benzene (density 0.88 g/ml) can be obtained from 33.6 l(N.O.) of acetylene?
225. To obtain isopropylbenzene, 70.0 ml of 2-bromopropane with a density of 1.314 g/ml and 39 g of benzene were taken. The volume of isopropylbenzene obtained was 55.5 ml (density 0.862 g/ml). Calculate the yield of isopropylbenzene.
Chapter 8
Alcohols are hydroxy derivatives of hydrocarbons in which the –OH group is not directly bonded to the carbon atoms of the aromatic ring.
According to the number of hydroxyl groups, monohydric and polyhydric alcohols are distinguished
(diatomic, triatomic and with a large number of hydroxyl groups). According to the nature of the hydrocarbon radical, saturated, unsaturated, cyclic, aromatic alcohols are distinguished. Alcohols in which the hydroxyl group is at the primary carbon atom are called primary, at the secondary carbon atom - secondary, at the tertiary carbon atom - tertiary.
For example:
butanol-1 butanol-2 2-methyl-propanol-2
(primary) (secondary) (tertiary)
allyl alcohol ethylene glycol glycerin
(unsaturated alcohol) (dihydric alcohol) (trihydric alcohol)
cyclopentanol benzyl alcohol
(cyclic alcohol) (aromatic alcohol)
8.1. Obtaining alcohols
1. Hydration of alkenes in an acidic medium:
R 1 -CH \u003d CH -R 2 + H 2 O (H +) R 1 -CH 2 -CH (OH) -R 2
For example:
CH 2 \u003d CH 2 + H 2 O (H +) CH 3 - CH 2 (OH)
2. Hydrolysis of alkyl halides in an acidic or alkaline medium:
CH 3 -CH 2 -CH 2 -Br + NaOH (H 2 O) CH 3 -CH 2 -CH 2 -OH + NaBr
3. Hydrolysis of esters:
a) in an acidic environment
CH 3 COOC 2 H 5 + H 2 O (H +) \u003d CH 3 COOH + C 2 H 5 OH
b) alkaline hydrolysis (saponification)
CH 3 COOC 2 H 5 + NaOH (H 2 O) CH 3 COONa + C 2 H 5 OH
benzene is organic chemical compound. Belongs to the class of the simplest aromatic hydrocarbons. It is produced from coal tar, when processed it turns out colorless liquid having a peculiar sweet smell.
Chemical formula - (C6H6,PhH)
Benzene is highly soluble in alcohol and chloroform. Perfectly dissolves fats, resins, waxes, sulfur, bitumen, rubber, linoleum. When ignited, it smokes strongly, the flame is bright.
Toxic and carcinogenic. It has a narcotic, hepatotoxic and hemotoxic effect.
Application at home and at work
Benzene is used in the chemical, rubber, printing and pharmaceutical industries.
It is used for the production of synthetic rubbers, fibers, rubber, plastics. Paints, varnishes, mastics, solvents are made from it. Included in the composition of motor gasoline, is an important raw material for the manufacture of various medicines.
Other products are synthesized from benzene: ethylbenzene, diethylbenzene, isopropylbenzene, nitrobenzene and aniline.
More recently, benzene was added to motor fuel, but due to the tightening of environmental requirements, this additive was banned. New standards allow its content in motor fuel to be up to one percent, due to its high toxicity.
Toxicologists find benzene in foods such as eggs, canned meat, fish, nuts, vegetables, and fruits. Up to 250 mcg of benzene can enter the human body with food per day.
How poisoning occurs
Benzene poisoning occurs through the respiratory system, less often by ingestion and contact with intact skin. The toxicity of benzene is very high, with prolonged interaction chronic intoxication may develop.
Acute poisonings are rare, they can be associated with accidents and accidents at work that have arisen due to violations of safety regulations. So, when cleaning tanks from under benzene, workers can develop lightning death.
Once in the body, benzene can cause irritation of the nervous system, profound changes in the bone marrow and blood. A short-term ingress of benzene vapor into the body does not cause changes in the nervous system.
If acute poisoning occurs, benzene and its homologues are found in the brain, liver, adrenal glands, and blood. In chronic poisoning, it enters the bone marrow and adipose tissue. It is excreted by the lungs in unchanged form.
Symptoms of acute benzene poisoning:
- headache;
- narcotic action syndrome;
- dizziness;
- noise in ears,
- convulsions;
- drop in blood pressure;
- small pulse;
- irritability;
- fast fatiguability;
- general weakness;
- bad sleep;
- depression;
- nausea and vomiting.
With mild or erased forms of intoxication, changes in the blood picture are hardly noticeable.
If benzene poisoning is of moderate severity, in addition to the above symptoms, bleeding from the nose and gums appears. In women, the menstrual period is shortened, there are abundant spotting. Usually such phenomena are accompanied by anemia. The liver is slightly enlarged, soreness is felt.
With severe intoxication, complaints of poor appetite, belching, pain in the right hypochondrium are not uncommon. The mucous membranes and skin become very pale, sometimes spontaneous hemorrhages occur. The liver is greatly enlarged, becomes painful. Decreased acidity and digestion.
From the side of the cardiovascular system, myocardial ischemia, tachycardia, and vascular hypotension may begin.
The nervous system in severe intoxication reacts differently. Sometimes manifestations of hyperactivity are noted, in other cases lethargy appears, reflexes of the lower extremities decrease
Without timely treatment, aleukemic myelosis gradually develops, less often lymphatic leukemia.
In the study of bone marrow punctate, the presence of atrophic processes in the bone marrow is detected. In some cases, its complete devastation is observed.
In chronic poisoning, which most often develop under industrial conditions, there are changes in the composition of the blood.
If the hands often come into contact with benzene, the skin becomes dry, cracks, bubbles, itching, swelling appear on it.
First aid and treatment
The main principle of therapy and prevention of benzene poisoning is the immediate cessation of contact with it at the first symptoms of poisoning. With chronic benzene intoxication, a complete recovery can occur if contact with benzene is stopped in a timely manner. If this is not done, severe intoxication will occur and, despite various methods therapy, the treatment will be ineffective.
When inhaling benzene vapor, doctors note the following clinical picture:
there is an excitation similar to alcohol, subsequently the patient loses consciousness, falls into a coma. The face turns pale, convulsions begin, characteristic muscle twitches. The mucous membranes are red, the pupils are dilated. The rhythm of breathing is disturbed, arterial pressure is reduced, the pulse is quickened. There may be bleeding from the nose and gums.
In this case, sodium hyposulfite, sulfur and glucose preparations are used, which help to speed up the process of neutralization of benzene and its oxidation products.
In case of acute intoxication, it is necessary to ensure the flow of fresh air. The victim is given artificial respiration. When vomiting, glucose is injected intravenously, if blood circulation is disturbed, injections of caffeine are given.
Bloodletting, intravenous infusions of glucose, cardiac drugs are carried out. If the patient is too agitated, bromide preparations are used.
In severe cases, with pronounced anemia, drugs that stimulate erythropoiesis, vitamin B12, folic acid, iron preparations together with ascorbic or hydrochloric acid. Do fractional blood transfusions.
Vitamin P is very effective in combination with ascorbic acid. To prevent the development of necrotic phenomena, penicillin and glucose are administered intravenously.
In case of toxic hepatitis resulting from chronic benzene poisoning, lipocaine, methionine, and choline are administered.
If benzene is taken orally, the clinical picture is as follows: in the mouth and behind the sternum, the patient feels an unbearable burning sensation, severe pain in the abdomen, accompanied by vomiting, excitation, followed by depression. Loss of consciousness may occur, convulsions, muscle twitches begin. Breathing becomes rapid at first, but soon slows down. The smell of bitter almonds is felt from the patient's mouth. The temperature drops sharply. The liver is enlarged, toxic hepatopathy is detected.
At very high concentrations of benzene, ingested, the face turns blue, the mucous membranes acquire a cherry red color. A person almost instantly loses consciousness, death occurs within a few minutes. If death does not occur after severe poisoning, health is severely undermined, and often death still occurs after a long illness.
If the poison is ingested, the stomach is washed through a probe, vaseline oil, sodium sulfate are injected into the vein, and sodium thiosulfate solution, cordiamine and glucose solution and ascorbic acid are injected into the vein. A caffeine solution is injected subcutaneously.
A solution of thiamine, pyridoxine hydrochloride and cyanocobalamin is injected intramuscularly. Antibiotics are prescribed to prevent infection. If there is bleeding, vikasol is injected into the muscle.
If the poisoning is mild, rest and warmth are required.
Prevention
In production where benzene is used, periodic medical examinations of all workers who come into contact with benzene are required. The therapist, neuropathologist and gynecologist participate in the examination - according to indications.
It is not allowed to accept for work in which contact with benzene is possible:
- people with organic diseases of the central nervous system;
- in all diseases of the blood system and secondary anemia;
- patients with epilepsy;
- with severe neurotic conditions;
- with all types of hemorrhagic diathesis;
- with diseases of the kidneys and liver.
It is forbidden to allow pregnant and lactating women, minors to work with benzene.