Assignments for the school stage of the All-Russian Chemistry Olympiad for schoolchildren (2) - Document. Drying organic liquids Wine spirit and its relatives
Option 5
Alcohols and phenols.
1. For an alcohol of composition C5H12O (I) and (II), the corresponding monochloro derivatives are obtained under the action of PCl5; upon dehydration of the latter, the same alkene 2-methyl-2-butene is obtained. Write the structural formulas of alcohols (I) and (II).
2. For what reason and under what conditions can monohydric alcohols react with each other? What substances are formed?
3. Give an explanation why the first representatives of alcohols are liquid substances.
4. Compose reaction equations in accordance with the diagram. Decipher the unknown substances - give their structural formula and name.
5. To burn 50 ml of methanol (p = 0.80 g/ml), volume of air is required:
a) 150l b) 200l c) 250l d) 180l
6. To completely neutralize a mixture of phenol and acetic acid, 46.8 ml of a 20% by weight KOH solution with a density of 1.2 g/ml is required; when the same mixture reacts with bromine water, 33.1 g of precipitate is formed. Determine the mass fractions of acetic acid and phenol in the initial mixture.
Test 90 min.
Option – 10
1) Make up the structural formulas of isomeric alcohols and ethers corresponding to the formula C3H8O. Name them.
2) To recognize ethanol and glycerol use:
a) Hydrogen chloride
c) Acetic acid
d) Copper(II) hydroxide
Write an equation for the reaction.
3) Write the equation of the chemical reactions that need to be carried out to obtain phenol from calcium carbide and indicate the conditions for their implementation.
4) Write the reaction equations with which you can carry out the following transformations:
Specify reaction conditions.
5) Bromine water was added to 50g of a 2.6% phenol solution until the end of the reaction. Determine what mass of 2% sodium hydroxide solution needs to be added to the reaction mixture to completely neutralize it. Write the reaction equation.
6) What mass of sodium phenolate can be obtained by reacting 4.7 g of phenol with a 4.97 ml sodium hydroxide solution (p = 1.38 g/ml)? The mass fraction of sodium hydroxide in the solution is 35%.
Test for 90 minutes
Option No. 4
1. Write the reaction equations by which 1-propanol can be converted into 2-propanol.
2. match the formula of the substance and the method of its preparation:
3. Acid properties are most pronounced in:
1) phenol 2) methanol 3) ethanol 4) glycerol
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5. When 13.8 g of ethanol was oxidized with copper (II) oxide weighing 28 g, 9.24 g of aldehyde was obtained with a practical yield:
A) 70% B) 75% C) 60% D) 85%
6. Calcium carbide was used to dehydrate ethanol. What is the mass (in grams) of calcium carbide that must be added to 150 ml of calcium alcohol with a density of p = 0.8 g/ml containing 96% ethanol to obtain anhydrous alcohol?
Test 90 min.
Option 12
1. The presence of a functional group in alcohol molecules does not affect:
A) solubility in water B) boiling point
B) structure of the hydrocarbon radical D) characteristic chemical properties
2. What chemical properties does the compound have, the structural formula of which is CH2=CH-CH2OH? Confirm your answer by composing the appropriate reaction equations. Specify the conditions for their implementation.
3. Two test tubes contain ethyl alcohol and ethylene glycol. How can you distinguish between these substances?
4. Create reaction equations in accordance with the transformation schemes:
Calcium carbide → acetylene → benzene → chlorobenzene → phenol → trinitrophenol
Specify the reaction conditions.
5. Calculate the mass of ethylene glycol that can be obtained from 200 g of an aqueous solution with a mass fraction of ethanol of 92%.
6. When 9 g of saturated monohydric alcohol was oxidized with copper (II) oxide, 9.6 g of copper was obtained. Determine the molecular formula of alcohol. Calculate the mass of the aldehyde formed if its yield is 90%
original mixture. Answer: volume fraction 40%; mass fraction 38.4%.
17.28. The composition of the hydrocarbon is expressed by the formula C3 H4. Hydrogen with a volume of 2.8 liters (normal conditions) was spent on the hydrogenation of this hydrocarbon weighing 5 g to the limiting compound. Determine the structural formula of the hydrocarbon and name it. Answer: cyclopropene.
18. AROMATIC HYDROCARBONS 18.1. Make up structural formulas of isomers corresponding to the formula
C8 H10 and containing an aromatic ring.
18.4. Write down reaction equations that can be used to carry out transformations:
methane → X → benzene
Name substance X. Specify the conditions for the reactions to occur. Answer: X - acetylene.
18.5. When dehydrogenating ethylbenzene weighing 4.24 g, styrene was obtained. The yield of the reaction product was 75%. What mass of a solution of bromine in carbon tetrachloride can the resulting styrene decolorize if the mass fraction of bromine in the solution is 4%?
18.6. What volume of hydrogen, measured under normal conditions, is formed during the cyclization and dehydrogenation of m-hexane with a volume of 200 ml and a density of 0.66 g/ml? The reaction proceeds with a yield of 65%. Answer: 89.4 l.
18.7. What volume of air, measured under standard conditions, will be required for complete combustion of 1,4-dimethylbenzene weighing 5.3 g? The volume fraction of oxygen in the air is 21%. Answer: 56 l.
18.8. By burning a benzene homologue weighing 0.92 g in oxygen, carbon monoxide (IV) was obtained, which was passed through an excess of calcium hydroxide solution. In this case, a precipitate weighing 7 g was formed. Determine the formula of the hydrocarbon and name it. Answer: C7 H8
18.9. An aromatic hydrocarbon, which is a homologue of benzene, weighing 5.3 g was burned to produce carbon monoxide (IV) with a volume of 8.96 l (normal conditions). Determine the formula of the hydrocarbon. How many isomers can this hydrocarbon have among benzene homologues? Write the structural formulas of these isomers. Answer: C8 H10; 4 isomeric homologues of benzene.
18.10. From acetylene with a volume of 3.36 l (normal conditions) we obtained
benzene volume 2.5 ml. Determine the yield of the product if the density of benzene is 0.88 g/ml. Answer: 56.4%.
18.11. When benzene was brominated in the presence of iron (III) bromide, hydrogen bromide was obtained, which was passed through an excess of silver nitrate solution. In this case, a precipitate weighing 7.52 g was formed. Calculate the mass of the resulting benzene bromination product and name this product. Answer: 6.28 g; bromobenzene
12.18. Benzene obtained by dehydrogenation of piclogexane with a volume of 151 ml and a density of 0.779 g/ml was subjected to chlorination under light. A chlorine derivative weighing 300 g was formed. Determine the yield of the reaction product. Answer: 73.6%.
18.13. A mixture of benzene and cyclohexene weighing 4.39 g decolorizes bromine water weighing 125 g with a bromine mass fraction of 3.2%. What mass of water is formed when the same mixture weighing 10 g is burned in oxygen?
18.14. A mixture of benzene and styrene of a certain mass decolorizes bromine water weighing 500 g with a mass fraction of bromine of 3.2%. When a mixture of the same mass was burned, carbon monoxide (IV) was released with a volume of 44.8 liters (normal conditions). Determine the mass fractions of benzene and styrene in the mixture. Answer: 60% benzene; 40% styrene.
19. ALCOHOLS AND PHENOLS
Nomenclature, properties and production of alcohols and phenols
19.4. How many isomeric alcohols can chloropropanol C3 H6 CIOH have? Write the structural formulas of the isomers and name them using substitutive nomenclature. Answer: 5 isomers.
19.5. How many phenols can be isomeric to 2-methyl-6-chlorophenol? Write the structural formulas of these phenols and name them. Answer: 12 isomeric phenols (not counting 2-methyl-6-chlorophenol).
19.6. How many isomeric tertiary alcohols can have the composition C6 H13 OH? Write the formulas of these alcohols and name them according to substitution nomenclature. Answer: three alcohols.
19.11. Three test tubes contain 1-butanol, ethylene glycol and a solution of phenol in benzene. What chemical reactions can be used to distinguish these substances? Write the equations for the corresponding reactions.
19.12. Three unlabeled test tubes contain liquids: n-propanol, 1-chlorobutane and glycerin. What chemical reactions can be used to distinguish these substances? Write the equations for these reactions.
Calculations using reaction equations involving saturated monohydric alcohols
19.14. What mass of sodium propoxide can be obtained by reacting propanol-1 weighing 15 g with sodium weighing 9.2 g?
19.15. When 1-butanol interacts with an excess of sodium metal, hydrogen is released, occupying a volume of 2.8 liters under normal conditions. How much of the substance butanol-1 reacted? Answer: 0.25 mol.
19.16. Methanol with an amount of 0.5 mol of the substance was heated with an excess of potassium bromide and sulfuric acid, to obtain bromomethane weighing 38 g. Determine the yield of bromomethane. Answer: 80%.
19.17. When dehydrating propanol-2, propylene was obtained, which decolorized bromine water weighing 200 g. The mass fraction of bromine in bromine water is 3.2%. Determine the mass of propanol-2 taken for the reaction.
Answer: 2.4 g.
19.18. When heating saturated monohydric alcohol weighing 12 g with concentrated sulfuric acid, an alkene weighing 6.3 g was formed. The product yield was 75%. Determine the formula of the original alcohol.
19.19. Determine the formula of a saturated monohydric alcohol if, upon dehydration of a sample with a volume of 37 ml and a density of 1.4 g/ml, an alkene weighing 39.2 g was obtained. Answer: C4 H9 OH.
19.20. Sodium weighing 12 g was placed in ethanol with a volume of 23 ml and a density of 0.8 g/ml. The mass fraction of water in ethanol is 5%. What volume of hydrogen will be released in this case? Calculate the volume under normal conditions.
19.21. What mass of metallic sodium will react with a solution of propanol-1 weighing 200 g, in which the mass fraction of water is 10%? What volume of hydrogen, measured under normal conditions, will be released during this reaction? Answer: 94.5 g Na; 46 g H2.
19.22. What mass of calcium carbide must be added to alcohol with a volume of 150 ml and a density of 0.8 g/ml to obtain absolute (anhydrous) alcohol,
if the mass fraction of ethanol in alcohol is 96%? What mass of absolute alcohol will be obtained in this case? Answer: 8.53 g CaC2; 115.2 g absolute alcohol.
19.23. From technical calcium carbide weighing 4 g, under the action of excess water, a gas with a volume of 1.12 liters can be obtained (normal conditions). What mass of technical carbide must be taken to obtain ethanol weighing 19.6 g, the mass fraction of water in which is 6%? Answer: 32
19.24. During the catalytic dehydration of ethanol weighing 1.84 g, a gas was obtained that reacted with bromine contained in a chloroform solution weighing 50 g. The mass fraction of bromine in this solution is 8%. Determine the yield of the alcohol dehydration product if the yield in the bromination reaction is quantitative. Answer: 62.5%.
19.25. A saturated monohydric alcohol weighing 30 g interacts with an excess of metallic sodium, forming hydrogen, the volume of which under normal conditions was 5.6 liters. Determine the formula of alcohol. Answer:
C3 H7 OH.
19.26. When producing synthetic rubber using the Lebedev method, ethanol is used as a feedstock, the vapors of which are passed over a catalyst, producing 1,3 butadiene, hydrogen and water. What mass of butadiene-1,3 can be obtained from alcohol with a volume of 230 l and a density of 0.8 kg/l if the mass fraction of ethanol in the alcohol is 95%? Please note that the product yield is 60%. Answer: 61.56 kg.
19.27. Methanol is produced by reacting carbon (II) monoxide with hydrogen. For the reaction, carbon (II) monoxide with a volume of 2 m3 and hydrogen with a volume of 5 m3 were taken (the volumes are normalized to normal conditions). As a result, methanol weighing 2.04 kg was obtained. Determine the yield of the product. Answer:
19.28. What mass of metallic sodium and absolute ethanol must be taken to obtain an ethanol solution weighing 200 g, the mass fraction of sodium ethoxide in which is 10.2%?
19.29. Determine the mass fraction of sodium alkoxide in its alcohol solution obtained as a result of the reaction between metallic sodium with a mass of 2.3 g and absolute ethanol with a volume of 50 ml and a density of 0.79 g/ml.
Answer: 16.3%.
19.30. From propanol-2 weighing 24 g, 2-bromopropane was obtained, which was used to obtain 2,3-dimethylbutane. What mass of dimethylbutane was formed if the yield of products at each stage of the synthesis was
60%? Answer: 6.2g.
19.31. When 2-butanol weighing 7.4 g reacted with an excess of hydrobromic acid, a bromine derivative was obtained, from which 3,4-dimethylhexane weighing 3.99 g was synthesized. Determine the yield of the reaction product. Answer: 70%.
19.32. By dehydration of a saturated monohydric alcohol, an alkene of a symmetrical structure with a straight chain weighing 8.4 g was obtained, which interacts with bromine weighing 24 g. Determine the structural formula of the starting alcohol and name it. Answer: butanol-2.
19.33. When saturated monohydric alcohol is heated with concentrated hydrobromic acid, a compound is formed in which the mass fraction of bromine is 73.4%. Determine the formula of the original alcohol. Answer: C2 H5 OH.
19.34. What volume of hydrogen, measured under normal conditions, can be obtained by reacting sodium metal weighing 1.6 g with a mixture of methanol and ethanol weighing 2.48 g? The mass fraction of methanol in the mixture is 25.8%, ethanol - 74.2%. Answer: 672 ml.
Calculations using reaction equations involving phenols
19.35. What mass of sodium phenolate can be obtained by reacting phenol weighing 4.7 g with a solution of sodium hydroxide with a volume of 4.97 ml and a density of 1.38 g/ml? The mass fraction of sodium hydroxide in the solution is 35%. Answer: 5.8 g.
19.36. When a solution of phenol in benzene weighing 200 g interacted with an excess of bromine water, a bromine derivative weighing 66.2 g was obtained. Determine the mass fraction of phenol in the solution. Answer: 9.4%.
19.37. There is a mixture of phenol and ethanol. Excess sodium metal was added to one half of the mixture to produce 672 ml of hydrogen (normal conditions). An excess of bromine solution was added to the other half of the mixture, and a precipitate weighing 6.62 g was formed. Determine the mass fractions of phenol and ethanol in the mixture.
19.38. To neutralize a mixture of phenol and ethanol, a solution with a volume of 50 ml with a mass fraction of sodium hydroxide of 18% and a density of 1.2 g/ml was used. The same mass of the mixture reacted with sodium metal weighing 9.2 g. Determine the mass fractions of phenol and ethanol in the mixture. Answer: phenol
80.9%; ethanol 19.1%. 20. ALDEHYDES
20.1. Write the structural formulas of the following aldehydes: 2-methylpentanal, 2,3-dimethylbutanal, hexanal.
20.4. What amount of formaldehyde is contained in a solution with a volume of Zli with a density of 1.06 g/ml, the mass fraction of CHgO in which is equal to
20%? Answer: 21.2 mol.
20.5. What volume of formaldehyde must be dissolved in water weighing 300 g to obtain formalin with a formaldehyde mass fraction of 40%? Calculate the volume under normal conditions. What mass of formaldehyde will be obtained? Answer: CH2 O volume 149.3 l; formalin weighing 500 g.
20.6. When ethanol weighing 13.8 g reacted with copper (II) oxide weighing 28 g, an aldehyde was obtained whose mass was 9.24 g. Determine the yield of the reaction product. Answer: 70%.
20.7. In industry, apetaldehyde is obtained using the Kucherov method. What mass of acetaldehyde can be obtained from commercial calcium carbide weighing 500 kg, the mass fraction of impurities in which is 10.4%? Acetaldehyde yield 75%. Answer: 231 kg.
20.8. During the catalytic hydrogenation of formaldehyde, alcohol was obtained, the interaction of which with an excess of sodium metal produced hydrogen with a volume of 8.96 liters (normal conditions). The yield of products at each stage of the synthesis was 80%. Determine the initial mass of formaldehyde. Answer: 37.5 g.
20.9. What mass of silver will be obtained as a result of the “silver mirror” reaction if an aqueous solution weighing 50 g with a mass fraction of propanal of 11.6% is added to an excess of an ammonia solution of silver oxide?
Answer: 21.6 g.
20.10. A volume of 280 ml of acetylene (normal conditions) was used to obtain acetaldehyde, the yield of which was 80%. What mass of metal can be obtained by adding all the resulting aldehyde,
to an excess of ammonia solution of silver oxide? Answer: 2.16 g.
20.11. An excess of ammonia solution of silver oxide was added to an aqueous solution weighing 4 g with a mass fraction of some aldehyde of 22%. In this case, a precipitate weighing 4.32 g was formed. Determine the formula of the original aldehyde.
20.12. When oxidizing alcohol vapor weighing 2.3 g over an excess of copper (II) oxide, aldehyde and copper weighing 3.2 g were obtained. What aldehyde was obtained? Determine the mass of the aldehyde if its yield is 75%. Answer: 1.65 g of acetaldehyde.
20.13. The mass fractions of carbon, hydrogen and oxygen in the aldehyde are 62.1, 10.3 and 27.6%, respectively. What volume of hydrogen is required to hydrogenate this 14.5 g aldehyde to alcohol? Calculate the volume under normal conditions. Answer: 5.6 l.
20.14. One of the industrial methods for producing aldehydes is heating alkenes with carbon monoxide (II) and hydrogen at elevated pressure in the presence of a catalyst. For this reaction, a volume of 140 liters of propylene (normal conditions) and an excess of other substances were taken. What mass of butanal and 2-methylpropanal will be obtained if the result is a mixture of these aldehydes, the mass fraction of butanal in which is 60%? Answer: 270 g of butanal and 180 g of 2-methylpropanal.
20.15. When some oxygen-containing organic substance weighing 1.8 g was oxidized with an ammonia solution of silver oxide, silver weighing 5.4 g was obtained. Which organic substance was subjected to oxidation? Answer: buta-nal.
20.16. From calcium carbide weighing 7.5 g, containing impurities (the mass fraction of impurities is 4%), acetylene was obtained, which was converted into an aldehyde using the Kucherov reaction. What mass of silver will be released when all the resulting aldehyde reacts with an ammonia solution of silver oxide? Answer: 24.3 g.
20.17. The oxidation of ethanol produced an aldehyde with 80% yield. When the same mass of ethanol interacts with metallic sodium, hydrogen is released, occupying a volume of 2.8 liters under normal conditions (the yield is quantitative). Determine the mass of aldehyde formed in the first reaction. Answer: 8.8 g.
20.18. What mass of formaldehyde with a formaldehyde mass fraction of 40% can be formed if you use aldehyde obtained from the catalytic oxidation of methane with a volume of 336 liters (normal conditions) with atmospheric oxygen? The yield of products in the oxidation reaction is 60%.
20.19. What mass of solution with a mass fraction of acetaldehyde of 20% is formed if the aldehyde was obtained with a yield of 75% from acetylene with a volume of 6.72 l (normal conditions) using the Kucherov reaction? Answer: 49.5 g.
20.20. When an aldehyde weighing 0.9 g was burned, carbon monoxide (IV) was formed, which reacted with a solution of sodium hydroxide with a volume of 16.4 ml and a density of 1.22 g/ml to form a medium salt. The mass fraction of sodium hydroxide in this solution is 20%. Determine the formula of burnt aldehyde. How many isomeric aldehydes can correspond to this formula? Write their structural formulas. Answer: butanal; 2 isomeric aldehydes.
21. CARBOXYLIC ACIDSNomenclature, chemical properties and production of carboxylic acids
21.2. Write the structural formulas of the following acids: 2-methylpropanoic acid, 2,3,4-trichlorobutanoic acid, 3,4-dimethylheptanoic acid.
21.3. How many isomeric carboxylic acids can correspond to the formula C5 H10 O2? Write the structural formulas of these isomers. Answer: 4 isomers.
21.4. Three unlabeled test tubes contain the following substances: ethanol, formic acid, acetic acid. By what chemical methods can these substances be distinguished?
21.5. Four test tubes contain the following substances: propionic acid, formaldehyde solution, phenol solution in benzene, methanol. What chemical reactions can be used to distinguish these substances?
21.6. How many isomeric monobasic carboxylic acids can correspond to the formula C6 H12 O2 ;? Write the structural formulas of these acids and name them according to substitutive nomenclature. Answer: 8 isomeric acids.
Calculation problems
21.11. What volume of vinegar essence with a density of 1.070 g/ml should be taken to prepare table vinegar with a volume of 200 ml and a density of 1.007 g/ml? The mass fraction of acetic acid in vinegar essence is 80%, in vinegar -6%.
21.12. What masses of solutions of acetic acid with a mass fraction of CH3 COOH of 90 and 10% must be taken to obtain a solution weighing 200 g with a mass fraction of acid of 40%? Answer: solution with a mass fraction of 90% - 75
G; 10% - 125 g.
21.13. The laboratory has a solution with a volume of 300 ml with a mass fraction of acetic acid of 70% and a density of 1.07 g/ml. What volume of water with a density of 1 g/ml must be added to the existing solution to obtain a solution with a mass fraction of acid of 30%? Neglect the change in volume when mixing the solution and water. Answer: 428 ml. 236
21.14. Ammonia with a volume of 4.48 liters (normal conditions) was passed through a solution of acetic acid weighing 150 g. Determine the mass fraction of CH3 COOH in the resulting solution, if the mass fraction of acid in the original solution was 20%.
21.15. Sodium hydroxide weighing 20 g was added to a solution weighing 300 g with a mass fraction of acetic acid of 30%. What volume of a solution with a mass fraction of potassium hydroxide of 25% is required to neutralize the solution obtained after adding sodium hydroxide? The density of the KOH solution is 1.24 g/ml. Answer: 180.6 ml.
21.16. Sodium bicarbonate was placed into a solution weighing 370 g with a mass fraction of propionic acid of 60%. As a result of the reaction, a gas with a volume of 11.2 liters was formed (normal conditions). Determine the mass fraction of propionic acid in the resulting solution. Answer: 47.4%.
21.17. What volume of a solution with a mass fraction of sodium hydroxide of 20% and a density of 1.22 g/ml will be required to neutralize a monobasic carboxylic acid weighing 14.8 g? The acid has the composition: carbon (mass fraction 48.65%), oxygen (43.24%), hydrogen (8.11%). Answer: 32.8
21.18. Determine the volume of methane that can be obtained by heating 50 g of acetic acid with an excess of sodium hydroxide. Please note that the mass fraction of water in the acid is 4%, and the gas yield is 75%. Volume
calculate under normal conditions. Answer: 13.44 l.
21.19. What mass of stearic acid C17 H35 COOH can be obtained from liquid soap containing potassium stearate weighing 96.6 g? The acid yield is 75%. Answer: 63.9 g. 238
21.20. What mass of solution with a mass fraction of acetic acid of 90% can be obtained by oxidizing 56 liters of butane (normal conditions) with atmospheric oxygen, if the acid yield is 60%? Answer:
21.21. Acetic acid can be prepared in three successive stages using calcium carbide as a starting material. For the reaction, technical calcium carbide weighing 200 g was taken, the mass fraction of impurities in which is 12%. What mass of acid will be obtained if the yield of products at the first stage of synthesis is 80%, at the second - 75%, at the third - 80%. Answer: 79.2 g.
21.22. When chlorine is passed into a solution with a mass fraction of acetic acid of 75%, chloroacetic acid is obtained. Determine its mass fraction in the solution, assuming that excess chlorine and hydrogen chloride are removed from the solution. Answer: 82.5%.
21.23. To neutralize the limiting monoprotic acid weighing 3.7 g, a solution of 5 ml with a mass fraction of potassium hydroxide of 40% and a density of 1.4 g/ml was used. Determine the formula of the acid.
21.24. Determine the formula of a limiting monobasic carboxylic acid if it is known that a solution with a volume of 15.75 ml with a mass fraction of sodium hydroxide of 25% and a density of 1.27 g/ml was spent on neutralizing a sample weighing 11 g. How many isomeric acids correspond to the found formula? Answer: C3 H7 COOH; two isomeric acids.
21.25. The oxidation of formic acid produced a gas, which was passed through an excess of calcium hydroxide solution. In this case, a precipitate weighing 20 g was formed. What mass of formic acid was taken for oxidation? Answer: 9.2g.
21.26. There is a solution of formic acid weighing 36.8 g. An excess of oxidizing agent was added to the solution. The gas obtained as a result of oxidation was passed through an excess of barite water, resulting in a precipitate weighing 39.4 g. Determine the mass fraction of acid in the original
- Each of the four substances, three of which are simple substances, and the fourth is an oxide of some element, is capable of interacting with the other three. Suggest possible formulas for such substances and provide equations for the corresponding chemical reactions.
- Calcium carbide and water can become raw materials for the production of such chemical compounds as: a) ethane, b) acetic acid, c) ethylene and polyethylene, d) vinyl chloride and polyvinyl chloride, e) benzene. Write the reaction equations for the production of these compounds, having at your disposal calcium carbide, water and any other inorganic substances.
- From what substance, as a result of sequential reactions of oxidation, exchange and substitution, can 3-nitrobenzoic acid be obtained without using other organic substances? Write the reaction equations and indicate the conditions for their occurrence.
- To decolorize equal volumes of bromine water of equal concentration, different amounts of the two isomers are required. Give examples of two pairs of such isomers, write the equations for the corresponding reactions.
- A volume of 10 ml of hydrocarbon gas is mixed with 70 ml of oxygen. The resulting mixture was set on fire. At the end of the reaction and after condensation of water vapor, the volume of the gas mixture was 65 ml. When the resulting gas mixture was passed through a sodium hydroxide solution taken in excess, its volume decreased to 45 ml. Determine the molecular formula of a hydrocarbon, assuming that the volumes of gases are measured under standard conditions.
- Letter from D.I. Mendeleev.
"Your Majesty! Allow me to give you a reprint of the message, from which it follows that I have discovered a new element……. At first I was of the opinion that this element fills the gap between antimony and bismuth in your remarkably insightfully constructed periodic table and that this element coincides with your ekaantimony, but everything points to the fact that here we are dealing with eka……. I hope to tell you soon more about this interesting substance; today I limit myself only to notifying you of the very likely triumph of your ingenious research and testifying to you my respect and deep respect.
Devotee………… ………….
Freiberg, Saxony.
February 26, 1886."Who wrote the letter to D.I. Mendeleev?
One of the few minerals that forms the one mentioned in D.I.’s letter. A periodic element that also contains sulfur and silver. The mass fractions of sulfur and silver in the mineral are 17.06% and 76.50%, respectively. Establish the formula of the mineral and give its name. Give an equation for the reaction of fusion of a mineral with soda in the presence of potassium nitrate. How can one isolate the simple substance discussed in the letter from the resulting alloy? Where is it used?
What methods exist for purifying this simple substance?
ethanol by Winkler, has a number of disadvantages: multiple
distillation, the product is contaminated with ammonia resulting from
hydrolysis of calcium nitride, which is contained as an impurity in calcium metal.
e) Calcium carbide is an effective desiccant, but pollutes
alcohol acetylene and other products. Currently, neither calcium metal nor its carbide is used for ethanol absolutization.
f) Anhydrous copper sulfate is advantageous in that its intensity
blue color can indicate the quality of the original alcohol and the end
process of absolutization. However, at present it is also
practically not used.
g) Azeotropic distillation of an alcohol-benzene mixture used for
for the production of absolute alcohol on a technical scale has also been developed for laboratory conditions. However, practically this
the method is not widely used.
h) Chloride coke was used for dehydration at 95°o
ethanol in the gas phase. This method produced 99.8% ethanol.
Calcium chloride is easily regenerated from the resulting solution.
i) Anhydrous calcium sulfate has also been proposed for ethanol drying. However, it is a relatively weak desiccant and is unsuitable
for complete dehydration of alcohol. In addition, with great content
water, a dihydrate is formed, which is difficult to remove from the flask.
Ethyl alcohol is often used as a solvent in the catalytic hydrogenation of various substances. In this case, the presence of a small amount of water usually does not matter, but it is important to remove substances that poison the catalyst. Pure 95% ethyl alcohol contains very little of these substances, and it is usually sufficient to distill it in a device with ground sections. In this case, the sections are thoroughly cleaned and not lubricated, and the first part of the distillate is discarded. Distilling alcohol over a small amount of Raney nickel is even more effective.
11.3. "-Propyl alcohol
“Propyl alcohol (bp 973) forms an azeotropic mixture with water, boiling at 88° and containing 71% propyl alcohol. Mixes with water in any ratio. Calcium oxide is used to dry it, and calcium hydride is used for final dehydration. When the water content is low, dehydration can be accomplished using sodium propnlate, prepared by dissolving sodium metal in propyl alcohol.
11.4. Isopropyl alcohol
Has t. kip. 82.4°, with water forms an azeotropic mixture with bp. 80° containing 87.4% isopropyl alcohol. Mixes with water in all respects. If the water content is high, isopropyl alcohol is pre-dried with sodium carbonate or potash and finally absolutized with calcium chloride. When the water content is low, calcium oxide is a good desiccant, which reduces the water content to 0.1%; For final dehydration, distillation over anhydrous copper sulfate is recommended. Additionally, all the methods mentioned above for ethyl alcohol can be used to dry isopropyl alcohol.
11.5. Butyl alcohols
“Butyl alcohol (bp. 118°) with water forms an azeotropic mixture with bp. 93°, containing 58% butyl alcohol.
Isobutyl alcohol (bp. 108°) gives an azeotropic mixture with water with bp. 90° containing 67% isobutyl alcohol.
emop-Butyl alcohol (bp. 99.5°) forms an azeotropic mixture with water bp. 87.5°, containing 73% emop-butyl alcohol.
/rzpem-Butyl alcohol (bp 82.5°) forms an azeotropic mixture with water, boiling at 80° and containing 88% mpem-butyl alcohol.
The first three of these alcohols have limited miscibility with water, and in most cases fractional distillation is sufficient to dry them. Chemical desiccants that can be used are calcium oxide, barium oxide, magnesium oxide, or the corresponding sodium alcoholate, obtained by dissolving sodium in this alcohol.
mpem-Butyl alcohol, on the other hand, is miscible with water in all proportions. This is a very valuable solvent, characterized by significant dissolving ability and great resistance to oxidizing agents, halogens, etc. If the water content is high, tert-butyl alcohol is pre-dried with calcium chloride. Small amounts of water are removed using calcium oxide or sodium metal. The high solidification temperature of tert-butyl alcohol (25.7°) allows it to be purified by fractional crystallization.
11.6. Higher aliphatic alcohols
For alcohols of this type, only physical constants are given below. The main method of their purification is distillation, for example with the addition of conventional desiccants (calcium oxide, barium oxide, etc.).
Isoamyl alcohol (bp 132e) forms an azeotropic mixture with water, boiling at 95° and containing 41% alcohol.
Optically active amyl alcohol, bp. 128°.
n-Hexyl alcohol (bp 157.5°) forms an azeotropic mixture with water, boiling at 98° and containing 20% alcohol.
2-Ethylbutanol-1 (bp 146°) image
In a chemistry circle, if you have a small electric arc furnace, as well as the required current source, you can get some calcium carbide. In a small graphite crucible or in a recess hollowed out in a thick carbon electrode, place a mixture of equal (by weight) quantities of calcium oxide (quicklime) and pieces of coke the size of a pinhead. Excess coal will burn when exposed to atmospheric oxygen. The experimental scheme is shown in the figure.
We bring the upper electrode into contact with the mixture, creating an electric arc. The mixture conducts current thanks to the pieces of coal. Let the arc burn for 20-30 minutes at the highest possible current. Eyes should be protected from bright light with glasses with very dark lenses (welding glasses).
After cooling, the mixture turns into a melt, which, if the experiment was successful, contains small pieces of carbide. To check this, place the resulting mass in water and collect the resulting gas bubbles in a test tube turned upside down and filled with water.
If there is no electric arc furnace in the laboratory, then gas can easily be obtained from commercially available calcium carbide. Let's fill several test tubes with gas - completely, half, one-third, etc. It is impossible to fill wider vessels, such as glasses, with gas, because water will flow out of them, and the glasses will contain mixtures of gas and air. When they ignite, as a rule, a strong explosion occurs.
Calcium carbide interacts with water according to the equation:
CaC 2 + 2H 2 O = Ca(OH) 2 + C 2 H 2
Along with calcium hydroxide (slaked lime), this reaction leads to the formation of ethyne, an unsaturated hydrocarbon with a triple bond. Thanks to this bond, ethylene exhibits high reactivity.
Ethyn research
Let's prove the presence of an unsaturated bond in ethyne (acetylene) using Bayer's reagent or bromine water. To do this, place the reagent in a test tube and pass ethyne through it. We will get it in another test tube from several pieces of calcium carbide. We close this test tube with a rubber stopper with two holes. We will insert a glass tube with a curved end into one of them in advance - it should be immersed in a test tube with the reagent. Insert a drip funnel into the other hole and first close the tap. M You can take a simple glass funnel instead, replacing the tap with a clamp, as when producing methane. Pour water into the funnel and, carefully opening the tap, slowly, drop by drop, add it to the carbide. Due to the explosive nature of ethylene, we will conduct the experiment near an open window or in a fume hood. Under no circumstances should there be open flames or turned on heating devices around.
Ethine in its pure state is a gas with a slightly intoxicating odor. Ethine obtained from technical carbide is always contaminated with unpleasant-smelling toxic impurities of hydrogen phosphorous (phosphine) and arsenous hydrogen (arsine). Mixtures of ethylene with air containing from 3 to 70% ethylene are explosive. Ethyne dissolves very easily in acetone. In the form of such a solution, it can be stored and transported in steel cylinders (Pure ethylene has almost no odor. Its mixtures with air explode from a spark in a wider range of ethylene concentrations - from 2.3 to 80.7%. - Note translation).
Ethine can be converted into a wide variety of compounds, which in particular have become important for the production of plastics, synthetic rubber, drugs and solvents. For example, when hydrogen chloride is added to ethyne, vinyl chloride (vinyl chloride) is formed - the starting material for the production of polyvinyl chloride (PVC) and plastics based on it. Ethanal is obtained from ethyne, which we will get to know later, and from it many other products are obtained.
In the GDR, the largest producer and at the same time consumer of ethylene is the synthetic butadiene rubber plant in Schkopau. Almost 90% of the giant enterprise's 400 products are derived in whole or in part from ethylene. In addition, large quantities of calcium carbide are produced by the nitrogen plant in Pisteritsa and the electrochemical plant in Hirschfeld. In 1936, 206,000 tons of carbide were produced in what is now the GDR. In 1946, production decreased to 30,000 tons, but already in 1951 it increased to 678,000 tons, and in 1955 it exceeded 800,000 tons. Since 1972, only the mentioned synthetic rubber plant has been receiving more than 1 million tons of carbide annually .
These figures indicate the enormous importance of calcium carbide and related processes.
In the future, carbide-based technology will increasingly be replaced by the more profitable petrochemical production established in the GDR in Schwedt and Leun 2. The main disadvantage of the carbide method for producing ethyne is the extremely high energy consumption. In fact, at the Szczkopau plant, only one modern carbide furnace consumes from 35 to 50 megawatts. But there are whole batteries of such stoves working there! More than 10% of all produced electricity is spent on the production of calcium carbide in the GDR.
SOME OF THE 800,000 CONNECTED
In 1828, a young German chemist, Professor Friedrich Wöhler, first obtained an organic compound - urea - by synthesis from inorganic starting substances. In the middle of the last century, Swedish chemist Jacob Berzelius synthesized more than 100 different organic compounds. (It is impossible not to mention here other founders of organic synthesis. In 1842, the Russian chemist N. N. Zinin first synthesized aniline, which was previously obtained only from plant materials. In 1845, the German chemist Kolbe synthesized acetic acid, in 1854 the French Bertlog- fats, in 1861 by A. M. Butlerov - a sugary substance. Interesting information about the life and work of these scientists is contained, in particular, in the book by K. Manolov “Great Chemists.” Vol. 1 and 2. Translated from Bulgarian (M., Publishing house "Mir", 1976), - Note translation)
Since then, thousands of chemists in all countries, through persistent and hard work, have created or isolated many new organic substances from natural sources. They investigated their properties and published the results of their work in scientific journals.
By the beginning of the 20th century. About 50,000 different organic compounds have already been studied, mostly obtained by synthesis. By 1930 the number had risen to 300,000, and at present the number of pure and trace-free organic compounds appears to be well over 800,000. However, the possibilities are far from being exhausted. Every day, more and more new substances are found and studied all over the world.
Most organic compounds have not found practical application. Many of them are known from personal experience only to a very narrow circle of chemists. Despite this, the labor expended was by no means in vain, since some substances turned out to be valuable dyes, medicines or new types of materials. It often happens that a substance that has been known for several decades and has long been described in the scientific literature suddenly acquires great practical importance. For example, the activity of some complex compounds against insect pests has recently been discovered. It is likely that other compounds that are still mentioned only in old, dust-covered scientific journals will soon find use as dyes, medicines, or in some other field. It is even possible that they will acquire exceptional importance in the national economy.
Now we will independently obtain and study several substances that are especially important in industry.
WINE ALCOHOL AND ITS RELATIVES
System first! When entering the world of organic chemistry, you can immediately get lost if you do not first familiarize yourself with the classes of organic compounds and the basics of the language of organic chemistry. In fact, most organic substances can be divided into groups with similar structures and similar properties. Chemists, using Latin and Greek roots, and, in addition, largely invented gobbledygook, created such a well-thought-out system of names that immediately tells a specialist to which class certain substances should be classified. One problem: along with the names according to the uniform rules of international nomenclature, for many compounds their own names are still used, related to the origin of these compounds, their most remarkable properties or other factors. Therefore, many compounds in this book will have multiple names.
We are already familiar with saturated and unsaturated hydrocarbons. Saturated hydrocarbons are called alkanes, unsaturated ones with a double bond are called alkenes, and those with a triple bond are called alkynes. We know that these hydrocarbons, if arranged in order of increasing number of carbon atoms, form homologous series.
Along with hydrocarbons, organic compounds that also contain oxygen are of great importance. Let us first consider three series of oxygen-containing organic compounds:
alkanols(alcohols)
alkanali(aldehydes)
alkanoic acids(formerly known as carboxylic acids)
Methane derivatives are the following compounds:
CH 3 -OH H-CHO H-COOH
methanol methanal methanoic acid
(methyl alcohol) (formaldehyde, (formic acid)
formic aldehyde)
Ethane derivatives are the following representatives of these three classes of compounds:
CH 3 -CH 2 -OH CH 3 - CHO CH 3 - COOH
ethanol ethanal ethanoic acid
(ethyl alcohol) (acetaldehyde, (acetic acid)
acetaldehyde)
Likewise, for all subsequent hydrocarbons, related or oxygen-containing compounds are known. In general, derivatives of any hydrocarbons correspond to the following formulas:
R-OHR-CHO R-COOH
alkanol alkanal alkanoic acid
(alcohol) (aldehyde) (carboxylic acid)
The number of possible compounds of these three classes will increase sharply if we take into account that in higher hydrocarbons each isomer forms different oxygen compounds. Thus, butane and isobutane correspond to different alcohols - butyl and isobutyl:
CH 3 -CH 2 -CH 2 -CH 3 CH 3 -CH 2 -CH 2 -OH
butane butanol-1
(butyl alcohol)
CH 3 -CH(CH 3)-CH 3 CH 3 -CH(CH 3)-CH 2 -OH
2-methylpropane 2-methylpropanol-1
(isobutane) (isobutyl alcohol)
In addition, additional isomers appear due to the fact that characteristic oxygen-containing groups, for example, the alcohol group OH, can be bonded either to the ends of the chain or to one of the intermediate carbon atoms. Examples include propyl and isopropyl alcohols:
CH 3 -CH 2 -CH 3 CH 3 -CH 2 -CH 2 -OH CH 3 -CH(OH)-CH 3,
propane propanol-1 propanol-2
(propyl alcohol) (isopropyl alcohol)
Groups characteristic of classes of compounds are called functional groups. These groups include, for example, the hydroxyl group OH of alkanols and the carboxyl group COOH of carboxylic acids. Later we will look at some examples of functional groups containing elements other than oxygen. Changing functional groups and introducing them into molecules of organic substances, as a rule, is the main task of organic synthesis.
Of course, in one molecule there can be several identical or different groups at the same time. We will learn about several representatives of this series of substances - compounds with several functions.
However, enough theory! Let us finally proceed to the experiments - we will obtain the above-mentioned oxygen-containing derivatives of methane and ethane, carry out their transformations and study their properties. These compounds, whose names have long been known to us, are very important for chemical technology. Let them help us become acquainted with the basics of industrial organic synthesis, although we will not be able to directly reproduce the industrial method of their production. They will also give us insight into the most important properties of compound classes.
Methanol research
By dry distilling wood, we have already obtained a few drops of crude methanol (methyl alcohol). Currently, the vast majority of methanol is obtained by synthesis from water gas:
CO + 2H 2 = CH 3 OH
The constituents of water gas combine to form methanol. In addition, higher alcohols are also formed in small quantities. This process requires a temperature of 400 °C, a pressure of 200 atm and is accelerated in the presence of oxide catalysts.
Methanol serves as a solvent and intermediate in the production of dyes. But its main consumer is the production of plastics, which requires large quantities of methanal (formaldehyde). Methanal is produced by the oxidation of methanol with atmospheric oxygen. In industry, a mixture of methanol vapor and air at 400 °C is passed over a copper or silver catalyst.
To simulate this process, bend a piece of copper wire with a diameter of 0.5-1 mm into a spiral and use tongs to bring it into the non-luminous zone of the Bunsen burner flame. The wire is heated and coated with a layer of copper (II) oxide. Let's place the methanol we obtained earlier (10 drops) in a fairly wide test tube and lower a hot copper spiral into it. As a result of heating, methanol evaporates and, under the influence of a catalyst - copper - combines with oxygen to form methanal (we recognize it by its characteristic pungent odor). In this case, the surface of the copper wire is restored. The reaction occurs with the release of heat. With large amounts of methanol vapor and air, the copper remains heated until the reaction is complete. Please note that methanol is very toxic! Therefore, we will not conduct experiments with large quantities.
Even a small sip of methanol can cause complete loss of vision and sometimes death. Therefore, methanol should always be stored in such a way that no one can drink it by mistake. However, methanol, along with other compounds, is specially added in small quantities to the alcohol used for combustion in order to denature it. Therefore, denatured alcohol is also poisonous!
Experiments with methanal
We will conduct the following experiments with commercial formaldehyde. Formalin is a 35-40% solution of methanal (formaldehyde) in water. Usually it still contains a small amount of unreacted toxic methanol. Methanal itself causes the coagulation of proteins and, therefore, is also a poison.
Let's carry out a series of simple experiments. In a test tube or small flask, evaporate a few milliliters of formaldehyde. The result will be a white, sparingly soluble mass, a sample of which we will then heat in another test tube. At the same time, it will evaporate, and by the smell you can feel that methanal has formed again. In its pure state, methanal is a gas that turns into liquid at normal pressure and –19 °C. Already in the cold and even more so with slight heating or in the presence of acids, methanal begins to polymerize. At the same time, many of its molecules connect with each other and form long chains of paraform:
CH 2 -O-CH 2 -O-CH 2 -O-CH 2 -O...
Strong heating leads to the reverse conversion of paraform to methanal.
Polymerization is characteristic of many alkanals and indicates the presence of an unsaturated bond in them. Polymerization reactions underlie the production of many plastics. Methanal gradually polymerizes in solution with the formation of increasingly longer chain molecules. Such polymerized formaldehyde can be regenerated by heating paraform and absorbing the methanal vapor released by water.
Methanal and other alkanals (aldehydes) give a characteristic color reaction with the so-called Schiff reagent, which can serve for their recognition. Let's prepare the reagent by taking a little fuchsin dye on the tip of a scalpel and dissolving it in a few milliliters of warm distilled water. To this solution, we will add an aqueous solution of sulfurous acid in portions until it becomes discolored. Pour a few milliliters of the reagent obtained in this way into a test tube, add a few drops of methanal solution and mix. A purple color will soon appear. After conducting a series of experiments with increasingly dilute methanal solution, we can verify the sensitivity of this qualitative reaction.
Let's pour a few milliliters of Fehling's reagent into a test tube, which can be prepared by mixing equal amounts of the following stock solutions:
Fehling's stock solution No. 1: 7 g copper (II) sulfate in 100 ml distilled water
Fehling's stock solution No. 2: 37 g of Rochelle salt and 10 g of sodium hydroxide in 100 ml of distilled water
Fehling's reagent itself is very unstable, and the original solutions can be stored. These solutions can sometimes be purchased in finished form in pharmacies.
Now add about 1 ml of methanal solution to the finished Fehling’s reagent and heat it to a boil. In this case, elemental copper is released, which forms a beautiful mirror coating on the walls of the test tube (copper mirror). You just need to first degrease the test tube with a chrome mixture. Other alkanals form a brick-red precipitate of copper(I) oxide.
Instead of Fehling's reagent, an ammonia solution of silver salt can be used. We will gradually add a dilute aqueous solution of ammonia to a dilute (approximately 2%) solution of silver nitrate - exactly until the precipitate that initially formed dissolves again. In a test tube, thoroughly washed with a chrome mixture and rinsed several times with distilled water, pour 2 ml of the prepared silver salt solution and 5-8 ml of methanal solution and carefully heat this mixture, preferably in a water bath. A distinct mirror forms on the walls of the test tube, and the solution, thanks to the tiny particles of silver that fall out, acquires an intense black color.
Alkanals (aldehydes) are very easily oxidized, resulting in the formation, as a rule, of alkanoic (carboxylic) acids. Thus, in relation to oxidizing agents they behave as reducing agents. For example, alkanals reduce cupric salt to copper(I) oxide or even elemental copper. They reduce an ammonia solution of silver salt to release metallic silver. These reactions are common to alkanals and other reducing agents, such as grape sugar, which we will discuss later.
Under the action of other oxidizing agents, alkanals are also oxidized to form alkanoic acids, and sometimes even to carbon dioxide and water. In a test tube, carefully add a 10% solution of hydrogen peroxide (peroxide) to several milliliters of methanal solution. Then heat the mixture and hold moistened blue litmus paper in the vapor over the test tube. Its redness indicates that methane (formic) acid has formed in the test tube.
We study methanoic acid
Methane (formic) acid is the simplest organic acid. In technology, it is obtained by adding carbon monoxide to sodium hydroxide under pressure. According to Eq.
NaOH + CO = HCOONa
in this case, the sodium salt of formic acid is formed - sodium methate, or sodium formate. It serves as an intermediate product in the production of other compounds and is used in textile and leather production. Methane acid has a strong disinfectant and preservative effect, so it is used to protect food products and silage from spoilage. Some preparations used for ensiling are mainly a solution of methanoic acid.
We will conduct the following experiments with methanoic acid purchased at the store. (Caution! Concentrated methane acid is poisonous and corrosive to the skin!)
Pour 5 ml of dilute sulfuric acid into a test tube and add a solution of potassium permanganate - enough so that the liquid is strongly colored. After this, add another 5 ml of approximately 80% methanoic acid. When heated, the mixture becomes discolored due to the reduction of permanganate to manganese (II) sulfate. In this case, methanoic acid is oxidized to carbon dioxide and water.
In subsequent test tube experiments, we will check whether magnesium, zinc, iron and nickel are dissolved in 60% methanoic acid. Active metals react with methane and other organic acids to form salts and release hydrogen. Thus, organic acids behave quite similarly to inorganic ones, but, as a rule, they are weaker.
Concentrated sulfuric acid and some catalysts decompose methane acid into carbon monoxide CO and water. Heat 1 ml of anhydrous methanoic acid with an excess of concentrated sulfuric acid in a test tube closed with a rubber stopper into which a glass tube is inserted. Gas escapes from this tube and, when ignited, burns with a pale blue flame. This is the poisonous carbon monoxide (carbon monoxide) that we are already familiar with. Due to the danger involved, the experiment should be carried out in a fume hood or outdoors.
In conclusion, it should also be noted that methanoic acid and its salts are often found in nature. As can be seen from its second name (formic), this acid is part of the poisonous secretions of ants. In addition, it is found in the secretions of bees, in nettles, etc.
Experiments with ethanol
So, we got acquainted with methanol, methanal and methanoic acid. Compounds like these, containing two carbon atoms, are of greatest importance in technology.
Ethanol (ethyl alcohol), commonly referred to simply as alcohol, is produced by what is known as alcoholic fermentation. Many types of sugars, as well as the saccharification product of starch in the presence of malt, are broken down by microscopically small yeast fungi to form alcohol and carbon dioxide. Anyone who has ever seen fruit juice ferment has observed the intense release of carbon dioxide from the outlet tube. And the fact that the resulting wine actually contains alcohol can be easily seen by the behavior of the person who drinks this wine.
Since alcoholic fermentation can occur spontaneously, diluted alcohol has been known to people since ancient times as an stimulating drink. There is hardly any need to talk about the disastrous consequences of drunkenness. Young people in particular should completely abstain from drinking alcoholic beverages.
The alcohol content during fermentation of sugar solutions and fruit juices varies widely. However, since yeast cannot exist at high alcohol concentrations, no more than 15% alcohol can be obtained through fermentation. Vodka and more concentrated alcohol are obtained from dilute solutions by distillation. Such distillation is legally permitted only at state-owned distilleries. The receipt of even the smallest amount of alcohol by private individuals, even for chemical experiments, is strictly prohibited by law.
Edible alcohol and alcohol for cosmetic purposes are produced only from grain (Potato starch is also used for this purpose. – Note translation). Starch is first converted into sugar, which is then fermented into alcohol. Industrial alcohol is obtained in large quantities as a result of fermentation of sulfite liquor, that is, from pulp and paper production waste. An increasingly large part of industrial alcohol - an indispensable solvent and starting material in organic synthesis - is currently produced synthetically from calcium carbide through ethylene and ethanal (The most advanced method for producing ethanol is its synthesis from ethylene (ethylene) by adding water to it in the presence of a catalyst . Note translation).
Pure alcohol goes on sale under the name rectified alcohol. It contains 4-6% water. Since rectification is expensive, we use it only in a few experiments. In cases where this is not specified, we will be content with much cheaper denatured alcohol, which, as we well know, is used as a fuel. This is also 95% alcohol, but so that it is not suitable for drinking, substances that are poisonous and have an unpleasant taste or odor (methanol, pyridine, phthalic acid ester) are added to it.
Since we still have a wide variety of experiments with alcohol ahead of us, for now we will limit ourselves to only two. Firstly, we can easily prove the presence of water in the rectified product. Heat several crystals of copper sulfate in a crucible until a colorless anhydrous salt is formed. Then add a pinch of the resulting salt to the alcohol sample and shake. The presence of water is detected by the blue color of the solution. Anhydrous alcohol, also called absolute alcohol, can only be obtained by processing with special drying agents.
Denatured alcohol serves as a good fuel for alcohol lamps and tourist stoves. Recently, it has even been used as rocket fuel. True, in campsites it is gradually being replaced by propane, which is delivered in small steel cylinders.
Many attempts are also being made to produce so-called “dry alcohol”. Its various varieties, as a rule, do not contain alcohol at all. We can also convert alcohol into a semi-solid state by dissolving about 5 g of soap shavings in 20 ml of denatured alcohol with stirring. The result is a gelatinous mass that can be cut into pieces. Like liquid alcohol, it burns with a pale blue flame.
Obtaining ethanal
The oxidation of ethanol produces ethanal (acetic aldehyde) and then ethanoic acid (acetic acid). Strong oxidizing agents immediately convert ethanal into acetic acid. Oxidation by air oxygen under the influence of bacteria also leads to the same result. We can easily verify this if we dilute the alcohol a little and leave it in an open cup for a while, and then check the reaction with litmus. To obtain table vinegar, they still mainly use acetic acid fermentation of alcohol or low-grade wines (wine vinegar). To do this, the alcohol solution is slowly passed through sawdust from beech wood under intensive air supply. 5% or 10% table vinegar or the so-called vinegar essence containing 40% acetic acid goes on sale (In the USSR, the concentration of food vinegar essence supplied to the retail chain is 80%, and the concentration of table vinegar is 9%.- Note translation). For most experiments it will suit us. Only in some cases will you need anhydrous (glacial) acetic acid, which is classified as a poison. You can buy it at a pharmacy or chemical store. Already at 16.6 °C it hardens into a crystalline mass similar to ice. Synthetically, acetic acid is obtained from ethyne through ethanal.
The repeatedly mentioned ethanal, or acetaldehyde, is the most important intermediate product in chemical technology based on the use of calcium carbide. It can be converted into acetic acid, alcohol, or butadiene, the starting material for synthetic rubber. Ethanal itself is produced industrially by adding water to ethyne. In the GDR, at the synthetic butadiene rubber plant in Schkopau, this process is carried out in powerful continuous reactors. The essence of the process is that ethine is introduced into heated dilute sulfuric acid, in which catalysts - mercury salts and other substances - are dissolved (This reaction was discovered by the Russian scientist M. G. Kucherov in 1881 - Note translation). Since mercury salts are very poisonous, we will not synthesize ethanal from ethyne ourselves. Let's choose a simpler method - careful oxidation of ethanol.
Pour 2 ml of alcohol (denatured alcohol) into a test tube and add 5 ml of 20% sulfuric acid and 3 g of finely ground potassium bichromate. Then quickly close the test tube with a rubber stopper into which a curved glass tube is inserted. Heat the mixture to a boil over a low flame and pass the resulting vapors through ice water. The resulting ethanal dissolves in water and can be detected with The essence of the reactions described above for the determination of alkanals. In addition, the solution exhibits an acidic reaction because oxidation easily proceeds further with the formation of acetic acid.
To obtain ethanal in larger quantities and more pure, we will assemble, guided by the drawing, a more complex installation. However, this experiment can only be performed in a circle or if the reader has extensive experience. Ethanal is poisonous and very volatile!
The left side of the installation is designed to pass a current of carbon dioxide (carbon dioxide). The latter is necessary to remove the evolved ethanal from the reaction sphere before it is oxidized further to acetic acid. Let's place pieces of marble in a flask and add dilute hydrochloric acid to them in small portions. To do this, you need a drip funnel with a long outlet tube (at least 25 cm). You can tightly attach such a tube to a regular drip funnel using a rubber hose. This tube must be filled with acid at all times so that carbon dioxide can overcome the excess resistance of the subsequent part of the installation and does not escape in the opposite direction (You can also use a dropping funnel without a long outlet tube. In this case, you need to insert another one short glass tube. We insert the same tube into the stopper closing the dropping funnel, and connect both tubes with a rubber hose. It is even more convenient to use the Kipp apparatus. - Note translation).
How to ensure equalization of pressure in the gas release device is shown in the figure on page 45.
First, pour 20 ml of denatured alcohol into another vessel that serves as a reactor - a 250 ml round-bottomed flask. Then dissolve 40 g of finely ground potassium or sodium dichromate (Poison!) in 100 ml of diluted sulfuric acid (Add 20 ml of concentrated sulfuric acid to 80 ml of water.) Due to the higher density of sulfuric acid, it is imperative to add it to water, and not vice versa. Sulfuric acid is always added gradually and only while wearing safety glasses. Under no circumstances should you pour water into sulfuric acid!
We immediately place one third of the prepared solution into the reactor, and the rest into a dropping funnel connected to the reactor. Let's insert a tube outlet into the reactor connecting it to a device for releasing carbon dioxide. This tube must be immersed in liquid.
Finally, the cooling system deserves special attention. In a tube that extends upward from the reactor at an angle, vapors of alcohol and acetic acid should condense. It is best to cool this tube using an external lead coil running running water through it. In extreme cases, we can do without refrigeration, but then we will get a dirtier product. To condense ethanal, which already boils at 20.2 °C, we use a direct refrigerator. It is, of course, advisable to take an efficient refrigerator - coil, ball or with internal cooling. In extreme cases, a not too short Liebig refrigerator will do. In any case, the cooling water must be very cold. Tap water is only suitable for this in winter. At other times of the year, you can pass ice water from a large tank installed at a sufficient height. We cool the receivers - two test tubes connected to each other - by immersing them in a cooling mixture of equal (by weight) quantities of crushed ice or snow and table salt. Despite all these precautions, ethanal vapor still partially escapes. Since ethanal has an unpleasant, pungent odor and is toxic, the experiment must be carried out in a fume hood or in the open air.
Only now, when the installation is charged and assembled, will we begin the experiment. First, let's check the operation of the gas release device by adding a small amount of hydrochloric acid to the marble. In this case, the installation is immediately filled with carbon dioxide. If it certainly passes through the reactor and no leaks are detected, we will proceed to the actual production of ethanal. We will stop the gas evolution, turn on the entire cooling system and heat the contents of the reactor to a boil. Since the oxidation of alcohol now releases heat, the burner can be removed. After this, we will again gradually add hydrochloric acid so that a moderate current of carbon dioxide passes through the reaction mixture all the time. At the same time, the remaining dichromate solution should flow slowly from the dropping funnel into the reactor.
At the end of the reaction, each of the two receivers contains several milliliters of almost pure ethanal. We plug the test tubes with cotton wool and store them in the cold for the next experiments. Long-term storage of ethanal is impractical and dangerous, since it evaporates too easily and, when in a bottle with a ground-in stopper, can forcefully knock out the stopper. Ethanal is sold only in sealed thick-walled glass ampoules.
Experiments with ethanal
In addition to the qualitative reactions described above, we can conduct a number of other experiments with small amounts of ethanal,
In a test tube, carefully add 1 drop of concentrated sulfuric acid to 1-2 ml of ethanal (wearing safety glasses and at a distance from you) using a glass rod. A violent reaction begins. As soon as it subsides, dilute the reaction mixture with water and shake the test tube. A liquid is released which, unlike ethanal, does not mix with water and boils only at 124 °C. It is obtained by combining three ethanal molecules to form a ring:
E that ethanal polymer is called paraldehyde. When distilled with dilute acids, it turns back into ethanal. Paraldehyde is used in medicine as a sleeping pill.
In the next experiment, we carefully heat a small amount of ethanal with a concentrated solution of sodium hydroxide. A yellow “aldehyde resin” is released. It also arises due to the addition of ethanal molecules to each other. However, unlike paraldehyde, the molecules of this resin are built from a large number of ethanal molecules.
Another solid polymerization product, metaldehyde, is formed when ethanal is cold treated with hydrogen chloride gas. Previously, it found some use as a solid fuel ("dry alcohol").
Dilute approximately 0.5 ml of ethanal with 2 ml of water. Add 1 ml of a diluted solution of sodium hydroxide or soda and heat for several minutes. We will smell an exceptionally pungent odor of crotonaldehyde. (Conduct the experiment in a fume hood or in the open air!).
From ethanal, as a result of the addition of two of its molecules to each other, an aldol is first formed, which is also an intermediate product in the production of butadiene. It contains both alkanal and alkanol functional groups.
By eliminating water, the aldol turns into crotonaldehyde:
SOLVENTS IN HOUSEHOLD AND TECHNOLOGY
These days, organic solvents can be found in any home. Who hasn't used a stain remover to remove grease or tar stains from clothes? All varnishes and many adhesives, such as rubber, also contain various organic solvents. If you have some experience, you can already tell by smell which substance serves as a solvent in these mixtures.
Organic solvents are required in almost any production. Fats and oils are extracted from plants using solvents. The plastics, textile and paint industries consume huge quantities of solvents. The situation is the same in the production of medicines and cosmetics, and in many other sectors of the economy.
Many people have probably encountered some of the main solvents, such as gasoline and alcohol. Many factors come into play when evaluating a solvent. First of all, of course, it is important which substances dissolve well in it. Thus, many resins, medicines and cosmetics dissolve well in alcohol, while fats and paraffin dissolve very poorly in it. In addition, when comparing solvents, their flammability, boiling point, toxicity and, last but not least, cost play a significant role.
We will carry out the following experiments with several compounds that are especially often used as solvents.
Carbon tetrachloride is a non-flammable solvent
If all four hydrogen atoms in methane are replaced with chlorine, you get carbon tetrachloride (carbon tetrachloride). Carbon tetrachloride is a liquid that boils at 76 °C and has a density of 1.593 g/cm 3 . Thus, it is much heavier than water and almost immiscible with it. Carbon tetrachloride excellently dissolves resins, fats, etc. and has a great advantage over other solvents: it does not burn. Against! Its heavy vapors suppress flames, which is why it is used in fire extinguishers.
Let's pour some gasoline, alcohol or acetone into a cup and carefully set fire to this flammable liquid in the open air. If we now add a few milliliters of carbon tetrachloride, the fire will go out. It should be taken into account that when extinguishing with carbon dioxide, a very poisonous gas, phosgene COCl 2, can be formed. Therefore, this fire extinguishing agent should only be used in enclosed spaces with appropriate precautions. Recently, fire extinguishers charged with carbon tetrachloride are falling out of use. Instead, fire extinguishers now use mixed bromine-chlorine or fluorine-chlorine derivatives of hydrocarbons.
In the next experiment, mix 2 ml of carbon tetrachloride with 1.5 g of zinc dust. The latter is a very fine powder, which is obtained by condensation of zinc vapor. Add more burnt magnesia or zinc oxide to the mixture to form a paste of medium viscosity. Place it on a piece of sheet iron or in an iron crucible and heat it in the open air over bare fire to 200 °C. In this case, a violent reaction begins, leading to an increase in the temperature of the mixture above 1000 °C. At the same time, thick smoke is released. Carbon tetrachloride and zinc react to form zinc chloride:
2Zn + CCl 4 = 2ZnCl 2 + C
Zinc chloride evaporates at high temperatures and forms a fog, attracting water from the air.
Other metals, especially iron, also react slowly with carbon tetrachloride. Therefore, it promotes corrosion and is not suitable as a solvent for metal varnishes and similar purposes.
Carbon tetrachloride is quite poisonous. Inhalation of its vapors in small doses has a narcotic effect, and in large doses or in so-called chronic poisoning leads to severe liver damage. Therefore, caution is required when working with carbon tetrachloride! Reliable ventilation will prevent the accumulation of carbon tetrachloride vapors in the air.
Propanone dissolves fat
The next important representative of the solvent group is propanone (acetone).
By dry distillation of wood, we obtained the calcium salt of acetic acid - “gray wood vinegar powder.” Anyone who has not carried out this experiment can easily prepare the indicated salt by neutralizing a dilute solution of acetic acid (table vinegar) with calcium carbonate or calcium hydroxide.
To obtain acetone, place a few grams of wood vinegar powder in a test tube made of refractory glass. We close the test tube with a rubber stopper, into the hole of which a curved glass tube is inserted. Let's cool this tube using a lead coil. The receiver can be a test tube immersed in ice water. Due to the flammability of the product, the outlet pipe should not be too short so that the distance between the flame and the receiver is as large as possible. In addition, we take into account that the experiment can only be carried out in a fume hood or in the open air.
Heat the test tube with powder strongly with a Bunsen burner. Vapors are released, and a mobile liquid condenses in the receiver, which, depending on the degree of purity of the original salt, has a color from yellow to brownish. It consists mainly of acetone, used as a fat solvent:
The excellent properties of this solvent can be easily verified by dissolving small amounts of fat, wax, varnish and other organic substances. Many plastics also dissolve in acetone or at least swell in it. Try using it on a piece of celluloid, polystyrene or other plastic. Needless to say, it is an excellent solvent, and, unlike carbon tetrachloride, it does not cause corrosion. But it is very flammable. To make sure of this, pour a little into a cup and set it on fire, carefully bringing the source of fire closer.
In its pure state, acetone (propanone) is a colorless liquid that boils already at 56.2 °C and has a peculiar, not unpleasant odor. Previously, it was obtained mainly by dry distillation of gray wood vinegar powder, and today it is produced by various methods, including from acetic acid by passing its vapor over a catalyst, oxidation of isopropyl alcohol and fermentation of starch under the influence of appropriate bacteria. In recent years, acetone has been produced simultaneously with phenol in a roundabout way - through the stage of cumene formation - from gases from petrochemical production.
In terms of its chemical structure, acetone is the simplest representative of alkanones (ketones), related to alkanals (aldehydes). While alkanals, such as methanal or ethanal, contain a C=O group at the end of the molecule, in alkanones such a group is located at the “internal”, i.e., not at the outermost carbon atom in the chain. Alkanones exhibit less unsaturation than alkanals and are therefore not detected by the qualitative reactions characteristic of alkanals. (Check!)
And finally, the broadcast
In conclusion, let's look at ether, which, in addition to its use in medicine for anesthesia, is an excellent solvent for fats and many other substances.
Strictly speaking, there are different ethers, which, like alkanals or alkanones, form a class of compounds with similar properties. Ordinary ether should strictly be called diethyl ether. It is formed from two molecules of ethanol by elimination of water, usually with concentrated sulfuric acid:
We get a small amount of ether. To do this, pour about 2 ml of denatured alcohol and 1.5 ml of concentrated sulfuric acid into a test tube. Let's select a stopper with two holes for the test tube. Into one of them we will insert a small dropping funnel or just a small funnel with an elongated tube, the exit from which will first be closed using a piece of rubber hose and a clamp. Using the second hole in the stopper, we attach a vapor cooling device to the test tube - the same as when producing ethanal. The receiver must be cooled with ice and water, because ether already boils at 34.6 °C! Due to its unusually easy flammability, the refrigerator should be as long as possible (at least 80 cm) so that there is sufficient distance between the source of fire and the receiver. For the same reason, we will conduct the experiment away from flammable objects, in the open air or in a fume hood. Pour about 5 more ml of denatured alcohol into the funnel and carefully heat the test tube on an asbestosed grid with a Bunsen burner to approximately 140 ° C (The temperature should not exceed 145 0 C, since at a higher temperature (about 170 0 C) ethene is formed. Even when working with low the amount of ether should always take into account the risk of fire. Therefore, we recommend replacing the burner with a closed electric stove and installing a protective screen between the heat source and the receiver. When using a dropping funnel, carefully lubricate and check the tap. As a receiver, it is best to take a test tube tightly attached to the refrigerator with a side outlet , onto which you can put a rubber hose to increase the distance between the escaping ether vapor and the heat source. It is better to cool the receiver with a mixture of ice and salt - Note translation). A very volatile distillate condenses in the receiver, and in case of insufficient cooling we will smell the characteristic smell of ether. Carefully opening the clamp, we will gradually add alcohol in small portions. At the end of the reaction, the sulfuric acid is increasingly diluted with the resulting water, as a result of which the formation of ether stops and the alcohol is distilled.
If the experiment is carried out carefully, we will obtain about 4 ml of a very mobile, transparent liquid, which consists mainly of ether. If you apply a few drops of it to your finger, you will feel a strong cold. The fact is that the ether quickly evaporates, and the heat of evaporation is taken away from its environment.
At chemical plants and in hospitals, very strong explosions occurred when working with ether. With prolonged contact with atmospheric oxygen and under the influence of sunlight, easily explosive peroxides are formed in the ether. Therefore, under no circumstances will we store more ether. We will not need it in any of the experiments recommended in this book. We will only need ether in a mixture with two parts of alcohol as a solvent for collodion. Therefore, we will immediately dilute the remainder of the ether with double the amount of alcohol and store it only in the form of this safe mixture in a securely closed dark brown glass bottle.
Prolonged inhalation of ether vapor causes loss of consciousness, which was first used in 1846 by Jackson and Morton for anesthesia (For this purpose, ether during a surgical operation was first used by Long (USA) in 1842, but this experiment was not published. - Note translation). Thoroughly purified ether is still used for this purpose. However, one can hope that the readers of this book are trustworthy and, of course, will not conduct dangerous, irresponsible and categorically unacceptable experiments of their own related to anesthesia.
Concluding this section on solvents, it should be emphasized that in the following parts of the book we will also get acquainted with other important solvents, for example, benzene and esters, which are excellent dissolvers of varnishes and plastics.
BENZENE DERIVATIVES
The carbon skeleton of the organic compounds we have looked at so far has been straight or branched chains. The German chemist August Kekule first discovered that the molecules of many other organic compounds are built like a ring. The most important ring (cyclic carbon compound) - benzene - is contained in an amount of 1-2% in coal tar, from which it is obtained.
Benzene is a colorless liquid that boils at 80.2 °C and solidifies at 5.5 °C. For those who store their reagents in an unheated room, the freezing of benzene is a sign that it is time to find a warmer place for the bottles with aqueous solutions so that they do not break when the water begins to freeze.
Benzene is highly flammable! Place a few drops of it on a watch glass and carefully hold a burning match. Benzene will ignite before the flame comes into contact with the liquid. It burns with a smoky flame, indicating a high carbon content. The gross formula of benzene is C 6 H 6. Thus, it has the same ratio of carbon and hydrogen as ethylene. Indeed, benzene is formed from three molecules of ethyne when the latter is passed through a hot iron or quartz tube. But under no circumstances will we carry out this reaction ourselves because of the danger of an explosion that will occur if air gets into the tube.
Despite the similarity in the composition of benzene and ethylene, their chemical properties are completely different. Using bromine water or Bayer's reagent, we can easily prove that benzene does not undergo reactions typical of unsaturated compounds. Obviously, this is due to its special structure. Kekule proposed a formula for benzene that contains three double bonds in a six-membered ring. However, according to new ideas, the stable structure of benzene is better explained by the fact that the “excess” valence electrons, as shown in the formula given in the middle, belong to the entire ring, forming a single “electron cloud”:
Benzene derivatives, of which several hundred thousand are now known, are formed by introducing functional groups into the ring, as well as as a result of the addition of additional rings or carbon side chains to the benzene ring. In the following experiments we will obtain and study some of the simplest and at the same time most important benzene derivatives in technology.
Nitrobenzene from benzene
Unlike open-chain hydrocarbons, for which this is very difficult, in aromatic hydrocarbons you can easily introduce the nitro group NO 2.
To obtain nitrobenzene, we first need 15 ml of benzene, 20 ml of concentrated sulfuric acid and 15 ml of concentrated nitric acid, and at the end of the experiment - water and diluted sodium hydroxide. Benzene is very poisonous; Under no circumstances should you inhale its vapors.
First of all, let's prepare all the necessary equipment. Let's select an Erlenmeyer flask with a capacity of 125 ml with a rubber stopper, into the hole of which a not too thin glass tube about 50 cm long is inserted. We will also need a separating funnel (capacity 150 ml), a water bath and a thermometer with a scale up to 100 ° C. Let's prepare two more pans - one with ice water, and the other with water heated to 60 °C.
Due to the risk of splashes in the eyes, this experiment - as always when working with concentrated acids - can only be carried out with safety glasses!
First place concentrated sulfuric acid in an Erlenmeyer flask and then very carefully, all the time slightly shaking the flask, add nitric acid in small portions. Cool the heated nitrating mixture by immersing the flask in cold water. Then insert a thermometer into the flask and begin to gradually add benzene, continuously stirring the liquid in the flask with a glass rod. The temperature should not exceed 50-60 °C. If it rises higher, then before adding the next portion of benzene, it is necessary to soak the flask in ice water. When all the benzene has been added, we will keep the flask with a vertically inserted tube for some more time in a bath of warm water, the temperature of which will be maintained from 50 to 60 ° C, adding hotter water if necessary.
After this, transfer the contents of the flask into a separatory funnel. We will find two layers: the top layer contains nitrobenzene, and the bottom contains excess nitrating mixture. Let's salt this mixture of acids, add about 30 ml of water to the separating funnel, shake vigorously and separate the nitrobenzene, which now, due to its high density, forms the lower layer. For further cleaning, it must be washed in the same way with a highly diluted solution of caustic soda and finally again with water.
Nitrobenzene is a pale yellow liquid with a boiling point of 210 °C and a density of 1.203 g/cm 3 at 20 °C. If during the experiment we allow an excessive increase in temperature, the nitrobenzene will be more colored due to the admixture of dinitrobenzene. Nitrobenzene is very poisonous (If nitrobenzene gets on the skin, the affected area should be washed with alcohol and then with warm water and soap. – Note translation). You should also beware of inhaling its harmful fumes, which have a characteristic strong odor of bitter almonds. Although such an aroma is needed in perfumery, the use of nitrobenzene for this is strictly prohibited due to its toxicity. Typically, safe benzaldehyde, which has the same odor, is used for the same purpose.
Aniline - the founder of dyes
N itrobenzene for us - just as for the chemical industry - is only an intermediate product. We will also move on and obtain from it by reduction aniline - the ancestor of synthetic dyes (This reaction is called the Zinin reaction. Russian chemist N.N. Zinin in 1842 first carried out the reduction of nitrobenzene into aniline under the action of ammonium sulfide. - Note translation).
To get the amino group NH 2, we must replace oxygen with hydrogen in the nitro group. In industry, nitrobenzene is currently usually reduced in the gas phase by passing its vapor in a mixture with hydrogen over a copper catalyst. We, working with small quantities, will prefer the older method, in which reduction is carried out in the liquid phase with hydrogen at the time of separation - in Latin this is in statu nascendi. To do this, we obtain hydrogen by the action of hydrochloric acid on iron filings or, better, on granulated zinc or tin.
Let's carry out the experiment as follows. In an Erlenmeyer flask - the same as when obtaining nitrobenzene - place 10 g of nitrobenzene and 15 g of iron filings or granulated zinc. First, add 5 ml of concentrated hydrochloric acid and immediately close the flask with a stopper into which a glass tube is inserted vertically. With gentle shaking, a violent reaction will begin. At the same time, the flask heats up, and it must be cooled with moderately cold water - so that the reaction does not stop completely. From time to time we will remove the plug with the tube and add another 5-8 ml of hydrochloric acid. When we add only 50 ml of hydrochloric acid, we wait until the reaction subsides, and in a fume hood or in the open air we heat the flask with the same glass tube in a water bath for 30 minutes to an hour.
Finally, dilute the reaction mixture with water and, to neutralize the acid, add a solution of soda ash or baking soda (sodium bicarbonate) to an alkaline reaction. To do this, transfer the mixture from the flask into a beaker and first add water, and then the specified solution. A brown liquid with a peculiar odor will be released. This is aniline, which can be separated by careful decantation. It is better, although more troublesome, to isolate it by steam distillation.
Attention! Aniline is a very strong poison, which should only be stored closed and labeled “poison”. When working with aniline, you must be careful not to inhale its vapors. It is best - just like diethyl ether - to store aniline only in the form of a diluted alcohol solution.
Aniline served as the starting material for the production of the first synthetic organic dyes. A long time ago, Runge discovered the first aniline dye, which is still used to detect aniline.
Mix a few drops of aniline with 10 ml of water and add a filtered aqueous solution of bleach. The intense violet color is explained by the formation of a dye, the complex structure of which was a difficult puzzle even for chemists of the 20th century. Let us save aniline for the next experiments and note in conclusion that most dyes these days are obtained not from aniline, but from other compounds.
Other representatives of the aromatic series
Of the other benzene derivatives, we mention here only phenol, toluene and naphthalene. Phenol was also in first discovered by Runge in coal tar. It is an aromatic compound with a hydroxyl group and is therefore similar to alkanols. However, unlike alkanols, phenol has a weakly acidic reaction and easily reacts with alkalis to form phenolates. Therefore, it can be dissolved in alkalis. We have already obtained related cresols from dry distillation of wood and semi-coking of brown coal. This can be proven by adding a solution of iron(III) chloride to the extract of wood tar or lignite tar and tar water. Phenol and related substances give a color from blue to blue-violet. True, for extracts of resin and tar, this color can be masked by their own brown color.
Pure phenol is a solid that melts at 40.8 °C and boils at 182.2 °C. At 16 °C it dissolves in 12 parts of water, and the resulting solution turns litmus paper red. (Check!) In turn, phenol also dissolves some water in itself and becomes liquid, even when only 5% water is dissolved in it! If we add water to solid phenol, we will first obtain a liquid solution of water in phenol, and with further addition of water, a solution of phenol in water.
Due to the growth of plastics production, phenol has become one of the most important intermediate products in the chemical industry. World production now appears to reach almost 200,000 tons per year. In the GDR, a significant amount of phenol is obtained from the semi-coking of brown coal. In addition, more and more phenol is produced through synthesis.
When two or three OH groups are introduced into the benzene ring, polyhydric phenols are formed. They are strong reducing agents and are therefore used as developers in photography, such as hydroquinone. Triatomic phenol - pyrogallol - easily absorbs even atmospheric oxygen.
Toluene is a benzene derivative in which one hydrogen atom is replaced by a methyl group. This liquid is similar in properties to benzene; it is used as a solvent and also for production in explosives. With the introduction of three nitro groups, toluene is converted into trinitrotoluene, one of the most powerful explosives. Cresols, formed in large quantities during semi-coking, are also toluene derivatives containing an OH group. They thus correspond to phenol.
U Let's remember naphthalene - this is the simplest representative of hydrocarbons with several rings. In it, both benzene rings share two carbon atoms. Such substances are called condensed aromatic compounds.
Coal tar contains almost 64% naphthalene. It forms shiny crystalline plates that melt at 80°C and boil at 218°C. Despite this, naphthalene evaporates quickly even at room temperature. If you leave naphthalene crystals open for several days, they will noticeably shrink and a pungent smell of naphthalene will appear in the room. Naphthalene used to be part of most anti-moth products. Now, for this purpose, it is increasingly being replaced by other substances that have a less intrusive odor.
In industry, large quantities of phthalic acid are produced from naphthalene - the starting material for the production of valuable dyes. Later we will make some dyes ourselves.
IN In conclusion, let's give another example heterocyclic compound. Heterocyclic are substances containing in the ring not only carbon atoms, but also atoms of other elements (one or more oxygen, nitrogen or sulfur atoms). This unusually broad range of compounds includes important natural substances such as indigo and morphine, as well as fragments of certain amino acid molecules.
Let's look at furfural. We see that its molecule contains a five-membered ring of four carbon atoms and one oxygen atom. Judging by the side chain, furfural can be said to be a heterocyclic alkanal.
Let's get furfural from bran
Place 50 g of bran in a conical or round-bottomed flask and mix it with 150 ml of 10-15% sulfuric acid solution. Distill about 100 ml of liquid from the flask. It contains about 1 g of dissolved furfural. Let's extract it from the distillate with ether or carbon tetrachloride and evaporate the organic solvent in a fume hood. Next, we will carry out only two simple qualitative reactions.
In the first experiment, we add a few drops of hydrochloric acid and a little aniline to a sample of the resulting solution. Already in the cold, a bright red color appears.
In the next experiment, we will again add hydrochloric acid and a few grains of phloroglucinol (this is a triatomic phenol) to the solution under study. When boiled, a cherry-red color will appear.
When boiled with dilute acids, certain types of sugars - pentoses - form furfural. Pentoses are found in bran, straw, etc. and can be detected by the above methods.
With these few (out of 800,000!) examples, we will finish our short journey into the world of organic compounds. In the following chapters we will look at some of the most important applications of organic chemistry.
5. Materials for every taste
PLASTICS YESTERDAY, TODAY AND TOMORROW
- Drying organic liquids Wine spirit and its relatives
- Laboratory work: Production of methane and experiments with it Calcium carbide was used to dehydrate ethanol
- Model of error in the form of a random elementary function Mathematical model of measurement results of measurement error
- Questions for subject and object Basic geometric shapes