What do amines react with? Amines

According to the nature of the hydrocarbon substituents, amines are divided into

General structural features of amines

As in the ammonia molecule, in the molecule of any amine, the nitrogen atom has an unshared electron pair directed to one of the vertices of the distorted tetrahedron:

For this reason, amines, like ammonia, have significantly pronounced basic properties.

So, amines, like ammonia, reversibly react with water, forming weak bases:

The bond of the hydrogen cation with the nitrogen atom in the amine molecule is realized using the donor-acceptor mechanism due to the lone electron pair of the nitrogen atom. Limit amines are stronger bases compared to ammonia, because. in such amines, hydrocarbon substituents have a positive inductive (+I) effect. In this regard, the electron density on the nitrogen atom increases, which facilitates its interaction with the H + cation.

Aromatic amines, if the amino group is directly connected to the aromatic nucleus, exhibit weaker basic properties compared to ammonia. This is due to the fact that the lone electron pair of the nitrogen atom is shifted towards the aromatic π-system of the benzene ring, as a result of which the electron density on the nitrogen atom decreases. In turn, this leads to a decrease in the basic properties, in particular the ability to interact with water. So, for example, aniline reacts only with strong acids, and practically does not react with water.

Chemical properties of saturated amines

As already mentioned, amines react reversibly with water:

Aqueous solutions of amines have an alkaline reaction of the environment, due to the dissociation of the resulting bases:

Saturated amines react with water better than ammonia due to their stronger basic properties.

The main properties of saturated amines increase in the series.

Secondary limiting amines are stronger bases than primary limiting amines, which in turn are stronger bases than ammonia. As for the basic properties of tertiary amines, when it comes to reactions in aqueous solutions, the basic properties of tertiary amines are much worse than those of secondary amines, and even slightly worse than those of primary ones. This is due to steric hindrances, which significantly affect the rate of amine protonation. In other words, three substituents "block" the nitrogen atom and prevent its interaction with H + cations.

Interaction with acids

Both free saturated amines and their aqueous solutions interact with acids. In this case, salts are formed:

Since the basic properties of saturated amines are more pronounced than those of ammonia, such amines react even with weak acids, such as carbonic:

Amine salts are solids that are highly soluble in water and poorly soluble in non-polar organic solvents. The interaction of amine salts with alkalis leads to the release of free amines, similar to how ammonia is displaced by the action of alkalis on ammonium salts:

2. Primary limiting amines react with nitrous acid to form the corresponding alcohols, nitrogen N 2 and water. For example:

A characteristic feature of this reaction is the formation of gaseous nitrogen, in connection with which it is qualitative for primary amines and is used to distinguish them from secondary and tertiary. It should be noted that most often this reaction is carried out by mixing the amine not with a solution of nitrous acid itself, but with a solution of a salt of nitrous acid (nitrite) and then adding a strong mineral acid to this mixture. When nitrites interact with strong mineral acids, nitrous acid is formed, which then reacts with an amine:

Secondary amines give oily liquids under similar conditions, the so-called N-nitrosamines, but this reaction does not occur in real USE tasks in chemistry. Tertiary amines do not react with nitrous acid.

Complete combustion of any amines leads to the formation of carbon dioxide, water and nitrogen:

Interaction with haloalkanes

It is noteworthy that exactly the same salt is obtained by the action of hydrogen chloride on a more substituted amine. In our case, during the interaction of hydrogen chloride with dimethylamine:

Getting amines:

1) Alkylation of ammonia with haloalkanes:

In the case of a lack of ammonia, instead of an amine, its salt is obtained:

2) Reduction by metals (to hydrogen in the activity series) in an acidic medium:

followed by treatment of the solution with alkali to release the free amine:

3) The reaction of ammonia with alcohols by passing their mixture through heated aluminum oxide. Depending on the proportions of alcohol / amine, primary, secondary or tertiary amines are formed:

Chemical properties of aniline

Aniline - the trivial name of aminobenzene, which has the formula:

As can be seen from the illustration, in the aniline molecule the amino group is directly connected to the aromatic ring. In such amines, as already mentioned, the basic properties are much less pronounced than in ammonia. So, in particular, aniline practically does not react with water and weak acids such as carbonic.

The interaction of aniline with acids

Aniline reacts with strong and moderately strong inorganic acids. In this case, phenylammonium salts are formed:

Reaction of aniline with halogens

As already mentioned at the very beginning of this chapter, the amino group in aromatic amines is drawn into the aromatic ring, which in turn reduces the electron density on the nitrogen atom, and as a result increases it in the aromatic nucleus. An increase in the electron density in the aromatic nucleus leads to the fact that electrophilic substitution reactions, in particular, reactions with halogens, proceed much more easily, especially in the ortho and para positions relative to the amino group. So, aniline easily interacts with bromine water, forming a white precipitate of 2,4,6-tribromaniline:

This reaction is qualitative for aniline and often allows you to determine it among other organic compounds.

The interaction of aniline with nitrous acid

Aniline reacts with nitrous acid, but due to the specificity and complexity of this reaction, it does not occur in the real exam in chemistry.

Aniline alkylation reactions

With the help of sequential alkylation of aniline at the nitrogen atom with halogen derivatives of hydrocarbons, secondary and tertiary amines can be obtained:

Obtaining aniline

1. Reduction of nitrobenzene with metals in the presence of strong non-oxidizing acids:

C 6 H 5 -NO 2 + 3Fe + 7HCl = + Cl- + 3FeCl 2 + 2H 2 O

Cl - + NaOH \u003d C 6 H 5 -NH 2 + NaCl + H 2 O

As metals, any metals that are up to hydrogen in the activity series can be used.

The reaction of chlorobenzene with ammonia:

C 6 H 5 -Cl + 2NH 3 → C 6 H 5 NH 2 + NH 4 Cl

Chemical properties of amino acids

Amino acids call compounds in the molecules of which there are two types of functional groups - amino (-NH 2) and carboxy- (-COOH) groups.

In other words, amino acids can be considered as derivatives of carboxylic acids, in the molecules of which one or more hydrogen atoms are replaced by amino groups.

Thus, the general formula of amino acids can be written as (NH 2) x R(COOH) y, where x and y are most often equal to one or two.

Since amino acids have both an amino group and a carboxyl group, they exhibit chemical properties similar to both amines and carboxylic acids.

Acidic properties of amino acids

Formation of salts with alkalis and alkali metal carbonates

Esterification of amino acids

Amino acids can enter into an esterification reaction with alcohols:

NH 2 CH 2 COOH + CH 3 OH → NH 2 CH 2 COOCH 3 + H 2 O

Basic properties of amino acids

1. Formation of salts upon interaction with acids

NH 2 CH 2 COOH + HCl → + Cl -

2. Interaction with nitrous acid

NH 2 -CH 2 -COOH + HNO 2 → HO-CH 2 -COOH + N 2 + H 2 O

Note: interaction with nitrous acid proceeds in the same way as with primary amines

3. Alkylation

NH 2 CH 2 COOH + CH 3 I → + I -

4. Interaction of amino acids with each other

Amino acids can react with each other to form peptides - compounds containing in their molecules a peptide bond -C (O) -NH-

At the same time, it should be noted that in the case of a reaction between two different amino acids, without observing some specific synthesis conditions, the formation of different dipeptides occurs simultaneously. So, for example, instead of the reaction of glycine with alanine above, leading to glycylanine, a reaction leading to alanylglycine can occur:

In addition, a glycine molecule does not necessarily react with an alanine molecule. Peptization reactions also take place between glycine molecules:

And alanine:

In addition, since the molecules of the resulting peptides, like the original molecules of amino acids, contain amino groups and carboxyl groups, the peptides themselves can react with amino acids and other peptides due to the formation of new peptide bonds.

Individual amino acids are used to produce synthetic polypeptides or so-called polyamide fibers. So, in particular, using the polycondensation of 6-aminohexanoic (ε-aminocaproic) acid, nylon is synthesized in industry:

The nylon resin obtained as a result of this reaction is used for the production of textile fibers and plastics.

Formation of internal salts of amino acids in aqueous solution

In aqueous solutions, amino acids exist mainly in the form of internal salts - bipolar ions (zwitterions):

Getting amino acids

1) The reaction of chlorinated carboxylic acids with ammonia:

Cl-CH 2 -COOH + 2NH 3 \u003d NH 2 -CH 2 -COOH + NH 4 Cl

2) Breakdown (hydrolysis) of proteins under the action of solutions of strong mineral acids and alkalis.

Amines are organic derivatives of ammonia containing an amino group NH 2 and an organic radical. In general, the formula of an amine is the formula of ammonia in which the hydrogen atoms are replaced by a hydrocarbon radical.

Classification

• According to how many hydrogen atoms in ammonia are replaced by a radical, primary amines (one atom), secondary, tertiary are distinguished. Radicals can be the same or different types.
• An amine may contain more than one amino group, but several. According to this characteristic, they are divided into mono, di-, tri-, ... polyamines.
• According to the type of radicals associated with the nitrogen atom, there are aliphatic (not containing cyclic chains), aromatic (containing a cycle, the most famous is aniline with a benzene ring), mixed (fat-aromatic, containing cyclic and non-cyclic radicals).

Properties

Depending on the length of the chain of atoms in the organic radical, amines can be gaseous (tri-, di-, methylamine, ethylamine), liquid or solid substances. The longer the chain, the harder the substance. The simplest amines are water soluble, but as you move to more complex compounds, the water solubility decreases.

Gaseous and liquid amines are substances with a pronounced smell of ammonia. Solids are practically odorless.

Amines exhibit strong basic properties in chemical reactions; as a result of interaction with inorganic acids, alkylammonium salts are obtained. The reaction with nitrous acid is qualitative for this class of compounds. In the case of the primary amine, alcohol and gaseous nitrogen are obtained, with the secondary, an insoluble yellow precipitate with a pronounced smell of nitrosodimethylamine; with the tertiary reaction does not go.

They react with oxygen (burn in air), halogens, carboxylic acids and their derivatives, aldehydes, ketones.

Almost all amines, with rare exceptions, are poisonous. So, the most famous representative of the class, aniline, easily penetrates the skin, oxidizes hemoglobin, depresses the central nervous system, disrupts metabolism, which can even lead to death. Toxic to humans and couples.

Signs of poisoning:

Dyspnea,
- cyanosis of the nose, lips, fingertips,
- rapid breathing and increased heartbeat, loss of consciousness.

First aid:

Wash off the chemical reagent with cotton wool and alcohol,
- provide access to clean air,
- call an ambulance.

Application

As a hardener for epoxy resins.

As a catalyst in the chemical industry and metallurgy.

Raw material for the production of polyamide artificial fibers, such as nylon.

For the manufacture of polyurethanes, polyurethane foams, polyurethane adhesives.

The initial product for the production of aniline is the basis for aniline dyes.

For the production of medicines.

For the manufacture of phenol-formaldehyde resins.

For the synthesis of repellents, fungicides, insecticides, pesticides, mineral fertilizers, rubber vulcanization accelerators, anti-corrosion reagents, buffer solutions.

As an additive to motor oils and fuels, dry fuel.

For obtaining photosensitive materials.

Urotropin is used as a food additive, as well as an ingredient in cosmetics.

In our online store you can buy reagents belonging to the class of amines.

methylamine

Primary aliphatic amine. It is in demand as a raw material for the production of medicines, dyes, pesticides.

diethylamine

secondary amine. It is used as an initial product in the production of pesticides, drugs (for example, novocaine), dyes, repellents, additives to fuel and motor oils. It is used to make reagents for corrosion protection, for beneficiation of ores, for curing epoxy resins, and for accelerating vulcanization processes.

Triethylamine

Tertiary amine. It is used in the chemical industry as a catalyst in the production of rubber, epoxy resins, polyurethane foams. In metallurgy - a hardening catalyst in non-firing processes. Raw material in the organic synthesis of medicines, mineral fertilizers, weed control agents, paints.

1-butylamine

Tert-butylamine, a compound in which a tert-butyl organic group is bonded to nitrogen. The substance is used in the synthesis of rubber vulcanization enhancers, drugs, dyes, tannins, weed and insect control preparations.

Urotropin (Hexamine)

polycyclic amine. A substance in demand in the economy. Used as a food additive, drug and drug component, ingredient in cosmetics, buffer solutions for analytical chemistry; as a dry fuel, polymer resin hardener, in the synthesis of phenol-formaldehyde resins, fungicides, explosives, corrosion protection agents.

The most common property of all organic compounds is their ability to burn. Ammonia itself burns and, in general, easily, but setting it on fire is not always easy. In contrast, amines ignite easily and burn most often with a colorless or slightly colored flame. In this case, the nitrogen of amines is traditionally oxidized to molecular nitrogen, since nitrogen oxides are unstable.

Amines ignite more easily in air than ammonia.

4NH 3 + 3O 2 = 2N 2 + 6H 2 O;

4C 2 H 5 NH 2 + 15O 2 \u003d 8CO 2 + 14H 2 O + 2N 2.

Basic properties

Primary, secondary and tertiary amines necessarily contain an unshared electron pair, as befits trivalent nitrogen. That is, amines in solution exhibit basic properties, or their solutions are bases. That is why amines in an aqueous solution turn litmus blue, and phenolphthalein turns crimson. Rice. 12.

Rice. 1 .

Rice. 2 .

Thanks to this electron pair, a donor-acceptor bond with a hydrogen ion can form:

C 2 H 5 NH 2 + H + \u003d C 2 H 5 NH 3 +.

Thus, like ammonia, amines exhibit the properties of bases:

NH 3 + H 2 O NH 4 OH;

C 2 H 5 NH 2 + H 2 O C 2 H 5 NH 3 OH.

Ammonia forms salts with acids ammonium, and amines - alkyl ammonium :

NH 3 + HBr = NH 4 Br ( ammonium bromide)

C 2 H 5 NH 2 + HBr \u003d C 2 H 5 NH 3 Br ( ethylammonium bromide)

Just as ammonia forms ammonium salts with acids, amines form the corresponding salts. These salts can be formed, as in the case of ammonia, not only in the reaction of aqueous solutions, but also in the gas phase, if the amines are sufficiently volatile.

That is, if you put nearby vessels with concentrated hydrochloric acid or even organic volatile, such as acetic, and a vessel with a volatile amine, then soon something resembling smoke without fire will appear between them in space, i.e., crystals will form corresponding to the salt of alkylamine . Rice. 3.

Rice. 3 .

Alkalis displace amines , which, like ammonia, weak bases, from alkylammonium salts:

NH 4 Cl + KOH \u003d NH 3 - + KCl + H 2 O;

CH 3 NH 3 Cl + KOH \u003d CH 3 NH 2 - + KCl + H 2 O.

The basic properties of amines are higher than those of ammonia. Why? The formation of a donor-acceptor bond with a hydrogen ion is the easier, the higher the electron density on the nitrogen atom. Hydrocarbon radicals contain many electrons and willingly "share" them with the nitrogen atom (Fig. 4).

Rice. 4. Donor-acceptor bond with a hydrogen ion

However, the basic properties of tertiary amines are less than those of secondary ones (compare basicity constants). Why? In a tertiary amine, the nitrogen atom is surrounded on all sides by hydrocarbon radicals, and its ability to enter into reactions is hindered.

Amines, like ammonia, are able to react with haloalkanes, replacing the halogen atom:

CH 3 Br + NH 3 = CH 3 NH 2 + HBr;

CH 3 NH 2 + CH 3 Br \u003d (CH 3) 2 NH + HBr;

(CH 3) 2 NH + CH 3 Br \u003d (CH 3) 3 N + HBr.

Tertiary amines can also replace the halogen, so the reaction can go further. A quaternary ammonium salt is formed - tetramethylammonium bromide (CH 3) 4 NBr:

(CH 3) 3 N + CH 3 Br = (CH 3) 4 N+ + Br-.

Summing up the lesson

In this lesson, the topic “Amino compounds. Classification, isomerism, names and physical properties. You repeated the genesis of oxygen-containing organic compounds and remembered some common properties of ammonia and water. Then we looked at how to get amino compounds. Studied their classification, isomerism, names and inherent physical properties .

Bibliography

1. Rudzitis G.E., Feldman F.G. Chemistry: Organic Chemistry. Grade 10: textbook for educational institutions: basic level / G. E. Rudzitis, F.G. Feldman. - 14th edition. - M.: Education, 2012.
2. Chemistry. Grade 10. Profile level: textbook. for general education institutions / V.V. Eremin, N.E. Kuzmenko, V.V. Lunin, A.A. Drozdov, V.I. Terenin. - M.: Bustard, 2008. - 463 p.
3. Chemistry. Grade 11. Profile level: textbook. for general education institutions / V.V. Eremin, N.E. Kuzmenko, V.V. Lunin, A.A. Drozdov, V.I. Terenin. - M.: Bustard, 2010. - 462 p.
4. Khomchenko G.P., Khomchenko I.G. Collection of problems in chemistry for those entering the universities. - 4th ed. - M.: RIA "New Wave": Publisher Umerenkov, 2012. - 278 p.

1. website ().
2. Chemistry.ssu.samara.ru ().
3. Himik.ru ().
4. Promobud.ua ().

Homework

1. Nos. 3, 4 (p. 14) Rudzitis G.E., Feldman F.G. Chemistry: Organic Chemistry. Grade 10: textbook for educational institutions: basic level / G. E. Rudzitis, F.G. Feldman. - 14th edition. - M.: Education, 2012.
2. Compare the properties of limiting amines and alcohols.
3. Write the reaction equations confirming the basicity of amines.

Amines - these are derivatives of ammonia (NH 3), in the molecule of which one, two or three hydrogen atoms are replaced by hydrocarbon radicals.

According to the number of hydrocarbon radicals that replace hydrogen atoms in the NH 3 molecule, all amines can be divided into three types:

The group - NH 2 is called an amino group. There are also amines that contain two, three or more amino groups.

Nomenclature

The word "amine" is added to the name of organic residues associated with nitrogen, while the groups are mentioned in alphabetical order: CH3NC3H - methylpropylamine, CH3N(C6H5)2 - methyldiphenylamine. For higher amines, the name is compiled, taking the hydrocarbon as a basis, adding the prefix "amino", "diamino", "triamino", indicating the numerical index of the carbon atom. Trivial names are used for some amines: C6H5NH2 - aniline (systematic name - phenylamine).

For amines, chain isomerism, functional group position isomerism, isomerism between types of amines is possible

Physical Properties

Lower limiting primary amines - gaseous substances, have the smell of ammonia, dissolve well in water. Amines with a higher relative molecular weight are liquids or solids, their solubility in water decreases with increasing molecular weight.

Chemical properties

Amines are chemically similar to ammonia.

1. Interaction with water - the formation of substituted ammonium hydroxides. Ammonia solution in water has weak alkaline (basic) properties. The reason for the main properties of ammonia is the presence of a lone electron pair at the nitrogen atom, which is involved in the formation of a donor-acceptor bond with a hydrogen ion. For the same reason, amines are also weak bases. Amines are organic bases.

2. Interaction with acids - the formation of salts (neutralization reactions). As a base, ammonia forms ammonium salts with acids. Similarly, when amines react with acids, substituted ammonium salts are formed. Alkalis, as stronger bases, displace ammonia and amines from their salts.

3. Combustion of amines. Amines are combustible substances. The combustion products of amines, as well as other nitrogen-containing organic compounds, are carbon dioxide, water and free nitrogen.

Alkylation is the introduction of an alkyl substituent into the molecule of an organic compound. Typical alkylating agents are alkyl halides, alkenes, epoxy compounds, alcohols, less often aldehydes, ketones, ethers, sulfides, diazoalkanes. Alkylation catalysts are mineral acids, Lewis acids and zeolites.

Acylation. When heated with carboxylic acids, their anhydrides, acid chlorides or esters, primary and secondary amines are acylated to form N-substituted amides, compounds with a fragment -C (O) N<:

The reaction with anhydrides proceeds under mild conditions. Acid chlorides react even more easily, the reaction is carried out in the presence of a base to bind the HCl formed.

Primary and secondary amines interact with nitrous acid in different ways. With the help of nitrous acid, primary, secondary and tertiary amines are distinguished from each other. Primary alcohols are formed from primary amines:

C2H5NH2 + HNO2 → C2H5OH + N2 +H2O

This releases gas (nitrogen). This is a sign that there is primary amine in the flask.

Secondary amines form yellow, sparingly soluble nitrosamines with nitrous acid - compounds containing the >N-N=O fragment:

(C2H5)2NH + HNO2 → (C2H5)2N-N=O + H2O

Secondary amines are hard to miss, the characteristic smell of nitrosodimethylamine spreads throughout the laboratory.

Tertiary amines simply dissolve in nitrous acid at ordinary temperatures. When heated, a reaction with the elimination of alkyl radicals is possible.

How to get

1. Interaction of alcohols with ammonia during heating in the presence of Al 2 0 3 as a catalyst.

2. Interaction of alkyl halides (haloalkanes) with ammonia. The resulting primary amine can react with excess alkyl halide and ammonia to form a secondary amine. Tertiary amines can be prepared similarly

Amino acids. Classification, isomerism, nomenclature, obtaining. Physical and chemical properties. Amphoteric properties, bipolar structure, isoelectric point. Polypeptides. Individual representatives: glycine, alanine, cysteine, cystine, a-aminocaproic acid, lysine, glutamic acid.

Amino acids- these are derivatives of hydrocarbons containing amino groups (-NH 2) and carboxyl groups -COOH.

General formula: (NH 2) f R(COOH) n where m and n most often equal to 1 or 2. Thus, amino acids are compounds with mixed functions.

Classification

isomerism

The isomerism of amino acids, as well as hydroxy acids, depends on the isomerism of the carbon chain and on the position of the amino group in relation to the carboxyl (a-, β - and γ - amino acids, etc.). In addition, all natural amino acids, except aminoacetic, contain asymmetric carbon atoms, so they have optical isomers (antipodes). There are D- and L-series of amino acids. It should be noted that all amino acids that make up proteins belong to the L-series.

Nomenclature

Amino acids usually have trivial names (for example, aminoacetic acid is called differently glycocol or iicin, and aminopropionic acid alanine etc.). The name of an amino acid according to the systematic nomenclature consists of the name of the corresponding carboxylic acid, of which it is a derivative, with the addition of the word amino- as a prefix. The position of the amino group in the chain is indicated by numbers.

How to get

1. Interaction of α-halocarboxylic acids with an excess of ammonia. In the course of these reactions, the halogen atom in halocarboxylic acids (for their preparation, see § 10.4) is replaced by an amino group. The hydrogen chloride released at the same time is bound by an excess of ammonia into ammonium chloride.

2. Hydrolysis of proteins. Complex mixtures of amino acids are usually formed during the hydrolysis of proteins, however, using special methods, individual pure amino acids can be isolated from these mixtures.

Physical Properties

Amino acids are colorless crystalline substances, readily soluble in water, melting point 230-300°C. Many α-amino acids have a sweet taste.

Chemical properties

1. Interaction with bases and acids:

a) as an acid (carboxyl group is involved).

b) as a base (amino group is involved).

2. Interaction within the molecule - the formation of internal salts:

a) monoaminomonocarboxylic acids (neutral acids). Aqueous solutions of monoaminomonocarboxylic acids are neutral (pH = 7);

b) monoaminodicarboxylic acids (acidic amino acids). Aqueous solutions of monoaminodicarboxylic acids have pH< 7 (кислая среда), так как в результате образования внутренних солей этих кислот в растворе появляется избыток ионов водорода Н + ;

c) diaminomonocarboxylic acids (basic amino acids). Aqueous solutions of diaminomonocarboxylic acids have pH > 7 (alkaline), because as a result of the formation of internal salts of these acids, an excess of OH - hydroxide ions appears in the solution.

3. The interaction of amino acids with each other - the formation of peptides.

4. Interact with alcohols to form esters.

The isoelectric point of amino acids that do not contain additional NH2 or COOH groups is the arithmetic mean between the two pK values: respectively for alanine .

The isoelectric point of a number of other amino acids containing additional acidic or basic groups (aspartic and glutamic acids, lysine, arginine, tyrosine, etc.) also depends on the acidity or basicity of the radicals of these amino acids. For lysine, for example, pI should be calculated from half the sum of pK" values ​​for α- and ε-NH2 groups. Thus, in the pH range from 4.0 to 9.0, almost all amino acids exist predominantly in the form of zwitterions with a protonated amino group and a dissociated carboxyl group.

Polypeptides contain more than ten amino acid residues.

Glycine (aminoacetic acid, aminoethanoic acid) is the simplest aliphatic amino acid, the only amino acid that does not have optical isomers. Empirical formula C2H5NO2

Alanine (aminopropanoic acid) is an aliphatic amino acid. α-alanine is part of many proteins, β-alanine is part of a number of biologically active compounds. Chemical formula NH2 -CH -CH3 -COOH. Alanine is easily converted into glucose in the liver and vice versa. This process is called the glucose-alanine cycle and is one of the main pathways of gluconeogenesis in the liver.

Cysteine ​​(α-amino-β-thiopropionic acid; 2-amino-3-sulfanylpropanoic acid) is an aliphatic sulfur-containing amino acid. Optically active, exists in the form of L- and D-isomers. L-cysteine ​​is a component of proteins and peptides and plays an important role in the formation of skin tissues. It is important for detoxification processes. The empirical formula is C3H7NO2S.

Cystine (chem.) (3,3 "-dithio-bis-2-aminopropionic acid, dicysteine) is an aliphatic sulfur-containing amino acid, colorless crystals, soluble in water.

Cystine is a non-encoded amino acid that is a product of the oxidative dimerization of cysteine, during which two cysteine ​​thiol groups form a cystine disulfide bond. Cystine contains two amino groups and two carboxyl groups and is a dibasic diamino acid. Empirical formula C6H12N2O4S2

In the body, they are found mainly in the composition of proteins.

Aminocaproic acid (6-aminohexanoic acid or ε-aminocaproic acid) is a hemostatic drug that inhibits the conversion of profibrinolysin to fibrinolysin. Gross-

formula C6H13NO2.

Lysine (2,6-diaminohexanoic acid) is an aliphatic amino acid with pronounced base properties; essential amino acid. Chemical formula: C6H14N2O2

Lysine is part of proteins. Lysine is an essential amino acid that is part of almost any protein, it is necessary for growth, tissue repair, production of antibodies, hormones, enzymes, albumins.

Glutamic acid (2-aminopentanedioic acid) is an aliphatic amino acid. In living organisms, glutamic acid in the form of glutamate anion is present in proteins, a number of low molecular weight substances, and in free form. Glutamic acid plays an important role in nitrogen metabolism. Chemical formula C5H9N1O4

Glutamic acid is also a neurotransmitter amino acid, one of the important members of the excitatory amino acid class. The binding of glutamate to specific receptors of neurons leads to the excitation of the latter.

Simple and complex proteins. peptide bond. The concept of the primary, secondary, tertiary and quaternary structure of the protein molecule. Types of bonds that determine the spatial structure of the protein molecule (hydrogen, disulfide, ionic, hydrophobic interactions). Physical and chemical properties of proteins (precipitation, denaturation, color reactions). isoelectric point. The value of proteins.

Squirrels - these are natural high-molecular compounds (biopolymers), the structural basis of which is polypeptide chains built from α-amino acid residues.

Simple proteins (proteins) are high-molecular organic substances consisting of alpha-amino acids connected in a chain by a peptide bond.

Complex proteins (proteids) are two-component proteins that, in addition to peptide chains (a simple protein), contain a component of a non-amino acid nature - a prosthetic group.

Peptide bond - a type of amide bond that occurs during the formation of proteins and peptides as a result of the interaction of the α-amino group (-NH2) of one amino acid with the α-carboxyl group (-COOH) of another amino acid.

The primary structure is the sequence of amino acids in a polypeptide chain. Important features of the primary structure are conservative motifs - combinations of amino acids that play a key role in protein functions. Conservative motifs are preserved in the course of species evolution; they often make it possible to predict the function of an unknown protein.

Secondary structure - local ordering of a fragment of a polypeptide chain, stabilized by hydrogen bonds.

Tertiary structure - the spatial structure of the polypeptide chain (a set of spatial coordinates of the atoms that make up the protein). Structurally, it consists of secondary structure elements stabilized by various types of interactions, in which hydrophobic interactions play an important role. In the stabilization of the tertiary structure take part:

covalent bonds (between two cysteine ​​residues - disulfide bridges);

ionic bonds between oppositely charged side groups of amino acid residues;

hydrogen bonds;

hydrophilic-hydrophobic interactions. When interacting with surrounding water molecules, the protein molecule "tends" to curl up so that the non-polar side groups of amino acids are isolated from the aqueous solution; polar hydrophilic side groups appear on the surface of the molecule.

Quaternary structure (or subunit, domain) - the mutual arrangement of several polypeptide chains as part of a single protein complex. Protein molecules that make up a protein with a quaternary structure are formed separately on ribosomes and only after the end of synthesis form a common supramolecular structure. A protein with a quaternary structure can contain both identical and different polypeptide chains. The same types of interactions take part in the stabilization of the quaternary structure as in the stabilization of the tertiary. Supramolecular protein complexes can consist of dozens of molecules.

Physical Properties

The properties of proteins are as diverse as the functions they perform. Some proteins dissolve in water, forming, as a rule, colloidal solutions (for example, egg white); others dissolve in dilute salt solutions; others are insoluble (for example, proteins of integumentary tissues).

Chemical properties

In the radicals of amino acid residues, proteins contain various functional groups that are capable of entering into many reactions. Proteins enter into oxidation-reduction reactions, esterification, alkylation, nitration, they can form salts with both acids and bases (proteins are amphoteric).

For example, albumin - egg white - at a temperature of 60-70 ° is precipitated from a solution (coagulates), losing the ability to dissolve in water.