In the section on the question Aniline is a representative of amines, structure, functional group !? given by the author Hair the best answer is Aniline (phenylamine) - organic compound with the formula C6H5NH2, the simplest aromatic amine. Contains the amino group -NH2. It is a colorless oily liquid with a characteristic odor, slightly heavier than water and poorly soluble in it, soluble in organic solvents. In air, it quickly oxidizes and acquires a reddish-brown color. Poisonous.
Aniline is characterized by reactions both at the amino group and at the aromatic ring. The features of these reactions are due to the mutual influence of atoms. On the one hand, the benzene ring weakens the basic properties of the amino group compared to aliphatic amines and even ammonia. On the other hand, under the influence of the amino group, the benzene ring becomes more active in substitution reactions than benzene. For example, aniline reacts vigorously with bromine water to form 2,4,6-tribromaniline (white precipitate).
Main method of production of aniline catalytic. reduction of nitrobenzene with hydrogen in the gas or liquid phase. The gas-phase process is carried out in a tubular contact apparatus at 250-350°C on a nickel- or copper-containing cat
С6Н5NO2 + 3H2 = C6H5NH2 + 2H2O + 443.8 kJ/mol
Aniline is separated from water by layering and purified by distillation; reaction water is neutralized biochemically. To obtain 1 ton of aniline, 1.35 tons of nitrobenzene, 800 m3 of H2 and 1 kg of catalyst are consumed.
In the liquid phase, aniline is obtained at an increase. H2 pressure (up to 1.1 MPa) and 160-170°C on nickel or palladium cat. at the same time distillation of water and aniline due to the heat of the district.
Type of lesson: a lesson of learning new material based on existing knowledge
The purpose of the lesson: To generalize, expand and systematize the knowledge and concepts of students in the studied section "Amines". Focus on the key concepts of the topic "Aniline".
Expected result: Knowledge will be summarized and systematized with a purpose.
Lesson objectives:
Educational:
Check knowledge on the studied section, consolidate new material deepen knowledge on the topic; summarize the studied material; check the assimilation of the material on the basis of creative tasks; to form the ability to apply the acquired knowledge in practice when performing exercises and solving problems;
Developing:
To contribute to the formation of the ability to evaluate a friend and oneself to develop the ability to express one's point of view, conduct a reasoned conversation, draw conclusions based on analysis; help students see the results of their work; to form in students the ability to highlight the main thing; develop cognitive activity and creativity.
Educational:
To cultivate an active life position, honesty, human decency; to educate students by means of a lesson self-confidence; bring students to the conclusion about the intrinsic value of human qualities.
During the classes
I Organizational and motivational stage (1 min)
The purpose of the stage (expected result): to motivate students to work actively
Stage tasks: Set students up for a high pace of the lesson
Greeting students in class. Today our lesson will be very intense, and we will face a number of tasks.
But first write down D-Z Slide 2 Homework
(diary entry)
1. § 52, § 51 repeat.
2. § 52, no. 4-6 in writing, 1-3 orally
I I Goal setting (1.5 min)
Purpose: To generalize knowledge on the passed section "Amines", to acquire knowledge on the topic of the lesson, to be able to compare aniline with other representatives of aromatic and aliphatic amines
Tasks: Slide 3 Tasks in the lesson
Recall the physical and chemical properties of amines; to continue to form the ability to compose reaction equations that characterize the properties of amines; get acquainted with the features of chemical processes in the section "Aniline"; continue to learn to see the cause of the flow of chem. reactions depending on the structure of the molecule; evaluate your work in class.
III main part. Learning new things based on known facts
The structure of amines and aniline
Learning new material based on existing knowledge
Amines - organic derivatives, in the molecule of which one, two or all three atoms are replaced by a hydrocarbon residue.
Accordingly, three types of amines are usually distinguished:
primary amine methylamine
CH3CH2—NH—CH2CH3
secondary amine diethylamine
H3CH2—N—CH2CH3
tertiary amine triethylamine
Amines are characterized by structural isomerism:
Isomerism of the carbon skeleton
Functional group position isomerism
Primary, secondary and tertiary amines are isomeric to each other (interclass isomerism).
Training on isomerism and amine nomenclature
Learning new material
Electronic structure of aniline
Amines in which the amino group is bonded directly to an aromatic ring are called aromatic amines.
The simplest representative of these compounds is aminobenzene, or aniline.
The main distinguishing feature of the electronic structure of amines is the presence of an unshared electron pair at the atom included in the functional group. This leads to the fact that amines exhibit the properties of bases.
There are ions that are the product of formal substitution of all hydrogen atoms in the ammonium ion for a hydrocarbon radical.
These ions are part of salts similar to ammonium salts. They are called quaternary salts.
Training on isomerism and nomenclature of aromatic amines
The study of the physical properties of aniline in comparison with the physical properties of amines
Physical properties of amines and aniline
The simplest amines (methylamine, dimethylamine, trimethylamine) are gaseous substances. The remaining lower amines are liquids that dissolve well in water. They have a characteristic smell reminiscent of the smell of ammonia.
Primary and secondary amines are capable of forming hydrogen bonds. This leads to a noticeable increase in their boiling points in comparison with compounds having the same molecular weight but unable to form hydrogen bonds.
Aniline is an oily liquid, sparingly soluble in water, boiling at 184°C.
Russian organic chemist, academician.
discovered (1842) the reduction reaction of aromatic nitro compounds and received aniline. He proved that amines are bases capable of forming salts with various acids. Aniline is of such great industrial importance that in just one reaction the name of this scientist can be inscribed in “golden letters in the history of chemistry.
Chemical properties of amines and aniline
The chemical properties of amines are determined mainly by the presence of an unshared electron pair at the nitrogen atom.
1. Amines as bases. The nitrogen atom of the amino group, like the nitrogen atom in the ammonia molecule, due to the lone pair of electrons can form a covalent bond according to the donor-acceptor mechanism, acting as a donor. In this regard, amines, like ammonia, are able to add a hydrogen cation, i.e., act as a base.
As you already know from the course, the reaction of ammonia with water leads to the formation of hydroxide ions. A solution of ammonia in water is alkaline reaction. Solutions of amines in water also give an alkaline reaction. But aniline is a weaker base and interacts reluctantly.
Ammonia reacts with acids to form ammonium salts. Amines are also capable of reacting with acids.
The main properties of aliphatic amines are more pronounced than those of ammonia. This is due to the presence of one or more donor alkyl substituents, the positive inductive effect of which increases the electron density on the nitrogen atom. Increasing the electron density turns nitrogen into a stronger electron pair donor, which increases its basic properties.
Similarly, aniline in reactions with acids has basic properties, but they are less pronounced than those of aliphatic amines.
In the case of aromatic amines, the amino group and the benzene ring have a significant effect on each other.
The amino group is an orientant of the first kind. The amino group has a negative inductive effect and a pronounced positive mesomeric effect. Thus, electrophilic substitution reactions (bromination, nitration) will lead to ortho- and para-substituted products.
Note that, unlike benzene, which is brominated only in the presence of a catalyst, iron(III) chloride, aniline is capable of reacting with bromine water. This is explained by the fact that the amino group, by increasing the electron density in the benzene ring (remember the similar effect of substituents in the molecules of toluene and phenol), activates the aromatic system in electrophilic substitution reactions. In addition, aniline, unlike benzene, is slightly soluble in water.
P-system conjugation benzene ring with a lone electron pair of the amino group leads to the fact that aniline is a significantly weaker base than aliphatic amines.
Show the features of the reactions of complete and incomplete oxidation of amines and aniline, the mutual transition of oxidation and reduction reactions.
ALL EXAMPLES OF HRM ARE WRITTEN, THE PRODUCTS ARE NAMED (the explanation is in the form of a heuristic conversation)
Obtaining amines and aniline
1. Preparation of amines from halogen derivatives
CH3CH2Br + NH3 -> CH3CH2NH2 C6H5Br + NH3 -> C6H5NH2
2. Obtaining primary amines by the reduction of nitro compounds - aliphatic and aromatic. The reducing agent is hydrogen "at the moment of release", which is formed by the interaction of, for example, zinc with alkali or iron with hydrochloric acid.
The use of amines and aniline
Amines are widely used for the production of drugs and polymeric materials. Aniline is the most important compound this class(scheme), which is used for the production of aniline dyes, drugs (sulfanilamide drugs), polymeric materials (anilino-formaldehyde resins), explosives, rocket fuel, pesticides.
"Active" or "reactive" dyes are the best choice of aniline dyes on the market today. This group of dyes has proven itself excellently for fabrics made from plant fibers (cotton, linen, viscose, hemp, bamboo, paper, jute, etc.).
IV Consolidation of the studied material
1. Specify the number of y-bonds in the methyl-phenyl-amine molecule:
a) 6; b) 5; at 7; d) 4.
2. What properties of aniline are explained by the influence of the phenyl radical on the amino group:
a) aniline enters into substitution reactions more easily than benzene;
b) the electron density in the aromatic ring is unevenly distributed;
c) unlike ammonia, an aqueous solution of aniline does not change the color of litmus;
d) how is the base aniline weaker than ammonia?
3. Write the graphical formulas of isomeric amines with the general molecular formula С4Н11N. Name these substances.
4. a) Get ammonium chloride from inorganic raw materials.
HC1 + KOH alcohol +HI +NH3 +HC1
b) Propanol-2 → ? →? →? →? →?
5. Find the mass of a 19.6% sulfuric acid solution that can react with 11.2 liters of methylamine (n.a.) to form a medium salt.
6. A mixture of phenol and aniline completely reacted with 480 g of bromine water with w (Br2) = 3%. 36.4 cm3 of NaOH solution (w = 10%, p = 1.2 g/cm3) was used to neutralize the reaction products. Determine mass fractions substances in the original mixture.
7. Neutralization of 30 g of a mixture of benzene, phenol and aniline requires 49.7 ml of 17% HC1 (p = 1.0 g/ml). In the reaction of the same amount of the mixture with bromine water, 99.05 g of a precipitate is formed. Find the mass fractions of the components in the original mixture.
V Evaluation of class activities. Reflection.
The main properties of aniline:
a) aromatic amine - aniline is of great practical importance;
b) aniline C 6 H 5 NH 2 is a colorless liquid that is poorly soluble in water;
c) has a light brown color when partially oxidized in air;
d) aniline is highly toxic.
The main properties of aniline are weaker than those of ammonia and amines of the limiting series.
1. Aniline does not change the color of litmus, but forms salts when interacting with acids.
2. If concentrated hydrochloric acid is added to aniline, then an exothermic reaction occurs and after cooling the mixture, the formation of salt crystals can be observed: + Cl - - phenylammonium chloride.
3. If you act on a solution of phenylammonium chloride with an alkali solution, then aniline will be released again: [C 6 H 5 NH 3] + + Cl - + Na + + OH - → H 2 O + C 6 H 5 NH 2 + Na + + CI - . Here the influence of the aromatic radical of phenyl - C 6 H 5 is expressed.
4. In aniline C 6 H 5 NH 2, the benzene nucleus displaces the unshared electron pair of the nitrogen of the amino group towards itself. At the same time, the electron density on nitrogen decreases and it binds the hydrogen ion more weakly, which means that the properties of the substance as a base are manifested to a lesser extent.
5. The amino group affects the benzene core.
6. Bromine aqueous solution does not react with benzene.
Ways to use aniline:
1) aniline- one of the most important products of the chemical industry;
2) it is the starting material for the production of numerous aniline dyes;
3) aniline is used in the production of medicinal substances, for example, sulfanilamide preparations, explosives, macromolecular compounds, etc. The discovery by Kazan University professor N.N. Zinin (1842) of the available method for obtaining aniline had great importance for the development of chemistry and the chemical industry.
1. The organic synthesis industry began with the production of dyes.
2. The wide development of this production became possible on the basis of the use of the reaction for obtaining aniline, now known in chemistry under the name Zinin reactions.
Features of the Zinin reaction:
1) this reaction consists in the reduction of nitrobenzene and is expressed by the equation:
C 6 H 5 -NO 2 + 6H → C 6 H 5 -NH 2 + 2H 2 O;
2) a common industrial method for producing aniline is the reduction of nitrobenzene with metals, such as iron (cast iron shavings), in an acidic environment;
3) the reduction of nitro compounds of the corresponding structure is a common method for obtaining amines.
74. Amino acids
Structure and physical properties.
1.Amino acids- these are substances whose molecules contain both the amino group NH 2 and the carboxyl group - COOH.
For example: NH 2 -CH 2 -COOH - aminoacetic acid, CH 3 -CH (NH 2) -COOH - aminopropionic acid.
2. Amino acids are colorless crystalline substances that are soluble in water.
3. Many amino acids taste sweet.
4. Amino acids can be considered as carboxylic acids, in the molecules of which the hydrogen atom in the radical is replaced by an amino group. In this case, the amino group can be located at different carbon atoms, which causes one of the types of amino acid isomerism.
Some representatives of amino acids:
1) aminoacetic acid H 2 N-CH 2 -COOH;
2) aminopropionic acid H 2 N-CH 2 -CH 2 -COOH;
3) aminobutyric acid H 2 N-CH 2 -CH 2 -CH 2 -COOH;
4) aminovaleric acid H 2 N-(CH 2) 4 -COOH;
5) aminocaproic acid H 2 N-(CH 2) 5 -COOH.
5. The more carbon atoms in an amino acid molecule, the more isomers with different positions of the amino group relative to the carboxyl group can exist.
6. In order to indicate the position of the group - NH 2 in relation to the carboxyl in the name of the isomers, the carbon atoms in the amino acid molecule are designated sequentially by the letters of the Greek alphabet: a) α-aminocaproic acid; b) β-aminocaproic acid.
Features of the structure of amino acids consist in isomerism, which can also be due to the branching of the carbon skeleton, as well as the structure of its carbon chain.
Ways to use amino acids:
1) amino acids are widely distributed in nature;
2) amino acid molecules are the building blocks of which all plant and animal proteins are built; amino acids necessary for the construction of body proteins, humans and animals receive as part of food proteins;
3) amino acids are prescribed for severe exhaustion, after heavy operations;
4) they are used to feed patients, bypassing the gastrointestinal tract;
5) amino acids are necessary as a remedy for certain diseases (for example, glutamic acid is used for nervous diseases, histidine for stomach ulcers);
6) some amino acids are used in agriculture for feeding animals, which positively affects their growth;
7) are of technical importance: aminocaproic and aminoenanthic acids form synthetic fibers - nylon and enanth.
Lesson objectives: on the example of analysis, to consolidate students' knowledge about chemical properties ah amines; give an idea of aromatic amines; show practical significance aniline as the most important product of the chemical industry.
Equipment: on the demonstration table - aniline, water, phenolphthalein, hydrochloric acid, alkali solution, test tubes.
Aniline is being studied in order to concretize general concept about amines and as the most important representative of this class of compounds.
In this regard, the lesson can be held in the form of a story with the maximum involvement of students to discuss tasks and questions:
Name the homologous series of hydrocarbons and indicate the features of their structure.
What substances are amines?
What is the formula for an aromatic amine?
How to prove that aniline exhibits basic properties? Write an equation for a chemical reaction.
Further, the attention of students is drawn to the reaction of the interaction of aniline with bromine, not dwelling on the effect of the amino group on the benzene ring, but only indicating that the structural features of the aniline molecule make it possible to carry out this reaction.
On the production and use of aniline for the manufacture of dyes, various pharmaceutical preparations, photoreagents, explosives, plastics, etc. the teacher tells.
In this lesson, in our opinion, it is advisable to note in the story about the production and use of aniline and the toxic effects of emissions from both production and by-products when using amino compounds.
Expanded lesson plan
When studying this topic, it is necessary to consolidate the main idea of the development organic matter and the reasons that give rise to their diversity; deepen the concept of covalent bond on examples of amines; expand knowledge of hydrogen bonds and amphoteric compounds.
Starting to consider the topic, they invite students to remember which nitrogen-containing compounds they know. Students name nitrobenzene, nitroglycerin, trinitrocellulose. Briefly repeat information about the properties of nitrobenzene and its preparation in the laboratory. At the same time, they draw up an equation for the reaction on the board, mark its type (substitution) and give a name (nitration reaction). To the question whether nitration reactions can be carried out saturated hydrocarbons students give an affirmative answer. After that, the equations of nitration reactions are written up to the fifth homologue. The teacher notes that for the first time these reactions were carried out by the Russian scientist M.I. Konovalov in 1886. By analogy with nitrobenzene, he gives names to newly obtained nitrogen-containing substances - nitromethane, nitroethane, etc. Next, the teacher briefly introduces students to the physical properties of the resulting homologues. Of the chemical properties of nitro compounds, their ability to be reduced by hydrogen should be emphasized. In order for students to be convinced of the formation of a homologous series of new nitrogen-containing substances and to name them independently, they make up the reaction equations:
CH 3 NO 2 + 3H 2 2H 2 O + CH 3 NH 2
C 2 H 5 NO 2 + 3H 2 2H 2 O + C 2 H 5 NH 2
C 3 H 7 NO 2 + 3H 2 2H 2 O + C 3 H 7 NH 2, etc.
Pay attention to the formation of a new functional group of atoms, - NH 2 - amino group. It should be noted here that they are called amines by the radicals that make up the molecule, with the addition of the word "amine". After that, students easily give names to the substances obtained: methylamine, ethylamine, etc. Comparing the previously recorded equations for nitration reactions with reduction reactions, they conclude that there is a genetic relationship between homologous series organic substances: hydrocarbons can be converted into nitro compounds, and nitro compounds into amines:
CH 4 + HNO 3 H 2 O + CH 3 NO 2;
CH 3 NO 2 + 3H 2 2H 2 O + CH 3 NH 2.
These compounds are fatty amines, since they are derived from saturated hydrocarbons. Then the physical properties of the first representatives of the amine series are described. Before proceeding to the study of their chemical properties, pay attention to the composition of the functional group. An amino group is an ammonia residue in which one hydrogen atom is replaced by a hydrocarbon radical. Further, it is proposed to consider amines as derivatives of ammonia. Students note that ammonia can be replaced by hydrocarbon radicals and two other hydrogen atoms. Then, depending on the number of hydrocarbon residues included in the molecule, amines can be
CH 3 NH 2, C 2 H 5 NH 2
primary
secondary
tertiary
In nature amines are found in the decomposition of protein compounds; for example, herring brine contains methylamine, dimethylamine, trimethylamine. All amines are derivatives of ammonia, so they must also have similarities with it. Students can solve this question on their own (by this lesson they should repeat the properties of ammonia). For example, one of the students writes down on the left side of the board the equations of reactions that characterize the chemical properties of ammonia (interaction with water, with acids, combustion in a stream of oxygen). These experiments are also demonstrated here, emphasizing the ability of ammonia burn only in a stream of oxygen.
Then, similar experiments are carried out with amines (see paragraphs 1.1.3.1.). Based on the experiments, conclusions are drawn about the properties of amines.
Unlike ammonia, amines burn in air. They conclude: amines are similar in chemical properties to ammonia, but unlike it, they burn in air. This property led the scientist Wurtz to the discovery of amines in 1848. During the explanations, in parallel with the properties of ammonia, the equations of reactions with amines are written on the right side of the board. As a result of comparing the properties of ammonia and amines, students are convinced that among organic substances there are substances with the properties of bases - organic bases. This is explained on the basis of the electronic structure, considering the example of the formation of the ammonium ion. It is recalled that out of five valence electrons of a nitrogen atom, three unpaired ones go to the formation of covalent bonds with hydrogen atoms, forming an ammonia molecule, and two paired electrons remain ungeneralized, free. Due to them, a covalent bond is established at the nitrogen atom with the hydrogen ion (proton) of water or acid. In this case, in the first case, hydroxyl ions are released, which determine the properties of the bases, in the second case, ions of the acid residue. Consider electronic structure amines:
Particular attention is paid to the lone electron pair of nitrogen, which, as in ammonia, goes to the formation of a covalent bond with a hydrogen proton. In this case, an organic compound is formed with the properties of bases (1) or salts (2), if the proton (ion) of hydrogen was from an acid:
The salt formula can also be written in a different way:
CH 3. NH 2. HC1
Hydrochloric methylamine
Students know that the properties of substances are determined by their structure. Comparing the electronic structure of ammonium hydroxide and methylammonium. they can determine which substances - amines or ammonia - are stronger bases.
It is worth recalling that the methyl radical is capable of pushing the electron density away from itself. Then an increased electron density arises on nitrogen and it will hold the hydrogen proton in the molecule more firmly. The hydroxyl ion is released, its concentration in the solution increases, therefore the fatty amines are stronger bases than ammonia. To consolidate the material, the teacher suggests the question: is dimethylamine and trimethylamine expected to strengthen or weaken the basic properties? Students know that the radical is able to push the electron density away from itself, so they independently conclude that two- and three-substituted amines should be stronger bases than monosubstituted ones. Two radicals will increase the electron density on nitrogen to a greater extent, and, consequently, nitrogen will hold the hydrogen ion more strongly, and hydroxide ions will begin to enter the solution, i.e. the strength of the basic properties of amines depends on the magnitude of the negative charge on the nitrogen atom: the larger it is, the greater the strength of the bases. It would seem that the tertiary amine should be the strongest base, but the experiment shows the opposite. Apparently, three methyl radicals shield the lone pair of nitrogen electrons, interfere with the free addition of hydrogen ions, and, consequently, little hydroxyl ions enter the solution, so the medium is weakly basic.
In order for students to better understand the genetic relationship between classes of organic substances, they analyze the formation of aromatic amines from the "ancestor" of all aromatic hydrocarbons - benzene through nitro compounds. First of all, they briefly recall the methods for obtaining fatty amines from saturated hydrocarbons, then they suggest recalling the properties of benzene studied earlier and explaining them based on the electronic structure of benzene. To do this, it is desirable to post a table of the electronic structure of benzene, to prepare a model of its molecule. Thus, students themselves will “stretch a thread” from benzene to phenylamine through nitrobenzene and easily write down the corresponding reaction equations.
Here they also demonstrate the experience of obtaining nitrobenzene in a flask with a reflux condenser. Write the equation for the corresponding reaction on the board. Then, an experiment is carried out to restore the resulting nitrobenzene to aniline. During the implementation of this experiment, students are informed about the reaction of N.N. Zinin and its importance for the national economy.
Then they demonstrate pure aniline (if the school has it), talking about its toxicity and its careful handling. Demonstrate some physical properties: state of aggregation, color, smell, solubility in water.
Then they proceed to the study of the chemical properties of aniline. By analogy with fatty amines, aniline is assumed to have basic properties. To do this, a few drops of phenolphthalein are poured into a glass in which the solubility of aniline in water was tested. The color of the solution does not change. Check the interaction of aniline with concentrated hydrochloric and sulfuric acids. After cooling the mixture, students observe the crystallization of salts, therefore, aniline exhibits the properties of bases, no weaker than fatty amines. In the course of the discussion of these experiments, they make up the reaction equations, give names to the substances formed.
Next, they demonstrate the interaction of aniline salts with alkali (we draw an analogy with ammonium salts). Here, in passing, the question is raised: in the form of what compounds are fatty amines found in herring brine, if it interacts with alkali to form amines? (As a rule, students answer: in the form of salts). They check their solubility in water and the interaction of aniline salts with oxidizing agents, for example, with potassium dichromate. This reaction detects substances of various colors. Students are informed that the production of numerous aniline dyes (including such valuable ones as synthetic indigo), medicinal substances, and plastics is based on the properties of aniline. In conclusion, they demonstrate the experience of the interaction of aniline with bleach. Note that this reaction is characteristic of aniline. For verification, it is proposed to detect aniline in a mixture of substances obtained in the course of an experiment on the reduction of nitrobenzene with metals. Students are once again convinced of the existence of a genetic connection between classes. To consolidate the studied, it is proposed to draw up reaction equations confirming the possibility of carrying out the following transformations:
Students will experience that the main properties of aniline are weakened in comparison with amines of the limiting series. This is explained by the influence of the aromatic radical of phenyl C 6 H 5 . For clarification, we again consider the electronic structure of benzene. Students remember that the mobile -electron cloud of the benzene nucleus is formed by six electrons (it is good to have a model of a molecule or a good drawing of a benzene molecule). It must be emphasized that in the benzene nucleus, instead of one hydrogen atom, there is an amino group, draw the electronic structure of the amine molecule and once again pay attention to the free lone pair of electrons of the nitrogen atom in the amino group, which interacts with the -electrons of the benzene ring. As a result, the electron density decreases on nitrogen, a free pair of electrons retains a hydrogen proton with less force, and few hydroxide ions enter the solution. All this determines the weaker basic properties of aniline, which was observed during its reaction with indicators.
The lone pair of electrons of the nitrogen of the amino group, interacting with the -electrons of the benzene nucleus, shifts the electron density to the ortho and para positions, making the benzene nucleus chemically more active in these places. This is easily confirmed by the experience of the interaction of aniline with bromine water, which is immediately shown:
In conclusion, students should pay attention to the relationship existing in nature between substances, to their development from simple to complex.
Amines entered our lives quite unexpectedly. Until recently, these were toxic substances, collision with which could lead to death. And now, after a century and a half, we are actively using synthetic fibers, fabrics, building materials, dyes, which are based on amines. No, they did not become safer, people were simply able to "tame" them and subdue them, deriving certain benefits for themselves. About which one, and we'll talk further.
Definition
For the qualitative and quantitative determination of aniline in solutions or compounds, a reaction with is used at the end of which a white precipitate in the form of 2,4,6-tribromaniline falls on the bottom of the test tube.
Amines in nature
Amines are found in nature everywhere in the form of vitamins, hormones, metabolic intermediates, they are also found in animals and plants. In addition, when living organisms rot, medium amines are also obtained, which, in a liquid state, spread an unpleasant smell of herring brine. The "cadaveric poison" widely described in the literature appeared precisely due to the specific ambergris of amines.
For a long time, the substances we are considering were confused with ammonia due to a similar smell. But in the mid-nineteenth century, the French chemist Wurtz was able to synthesize methylamine and ethylamine and prove that they release hydrocarbons when burned. This was the fundamental difference between the mentioned compounds and ammonia.
Obtaining amines in industrial conditions
Since the nitrogen atom in amines is in the lowest oxidation state, the reduction of nitrogen-containing compounds is the simplest and most affordable way to obtain them. It is he who is widely used in industrial practice because of its cheapness.
The first method is the reduction of nitro compounds. The reaction during which aniline is formed is named by the scientist Zinin and was carried out for the first time in the middle of the nineteenth century. The second method is to reduce amides with lithium aluminum hydride. Primary amines can also be reduced from nitriles. The third option is alkylation reactions, that is, the introduction of alkyl groups into ammonia molecules.
Application of amines
By themselves, as pure substances, amines are used little. One rare example is polyethylenepolyamine (PEPA), which makes epoxy resin easier to cure in the home. Basically a primary, tertiary or secondary amine is an intermediate in the production of various organics. The most popular is aniline. It is the basis of a large palette of aniline dyes. The color that will turn out at the end depends directly on the selected raw material. Pure aniline gives blue color, and the mixture of aniline, ortho- and para-toluidine will be red.
Aliphatic amines are needed to obtain polyamides such as nylon and others. They are used in mechanical engineering, as well as in the production of ropes, fabrics and films. In addition, aliphatic diisocyanates are used in the manufacture of polyurethanes. Due to their exceptional properties (lightness, strength, elasticity and the ability to attach to any surface), they are in demand in construction (mounting foam, glue) and in the shoe industry (anti-slip soles).
Medicine is another area where amines are used. Chemistry helps to synthesize antibiotics of the sulfonamide group from them, which are successfully used as second-line drugs, that is, reserve ones. In case bacteria develop resistance to essential drugs.
Harmful effects on the human body
It is known that amines are very toxic substances. Harm to health can be caused by any interaction with them: inhalation of vapors, contact with open skin, or ingestion of compounds into the body. Death occurs from a lack of oxygen, since amines (in particular, aniline) bind to blood hemoglobin and prevent it from capturing oxygen molecules. Alarming symptoms are shortness of breath, blue nasolabial triangle and fingertips, tachypnea (rapid breathing), tachycardia, loss of consciousness.
In case of contact with these substances on bare areas of the body, it is necessary to quickly remove them with cotton wool previously moistened with alcohol. This must be done as carefully as possible so as not to increase the area of \u200b\u200bcontamination. If symptoms of poisoning appear, you should definitely consult a doctor.
Aliphatic amines are a poison for the nervous and cardiovascular systems. They can cause depression of liver function, its degeneration and even oncological diseases of the bladder.
