Amines, amino acids. Polycondensation of adipic acid, hexamethylenediamine and aminocaproic acid
Polymers.
Polymers(Greek πολύ- - many; μέρος - part) - these are complex substances, the molecules of which are built from many repeating elementary units - monomers.
Polymers are macromolecular compounds with large molecular weights (on the order of hundreds, thousands and millions).
The following two processes lead to the formation of macromolecular compounds:
1. Polymerization reaction,
2. Polycondensation reaction.
polymerization reaction
polymerization reaction is the process, as a result of which the molecules of a low molecular weight compound ( monomer) combine with each other, forming a new substance ( polymer), the molecular weight of which is an integer number of times greater than that of the monomer.
Polymerization, mainly characteristic of compounds with multiple bonds (double or triple). Multiple bonds during the polymerization reaction are converted into simple (single). The valence electrons released as a result of this transformation are used to establish covalent bonds between monomers.
An example of a polymerization reaction is the formation of polyethylene from ethylene:
Or in general terms:
A characteristic feature of this reaction is that as a result only the substance of the polymer is formed and no side substances are released, while. This explains the multiplicity of the weights of the polymer and the initial monomers.
Polycondensation reaction
Polycondensation reaction– the process of polymer formation from low molecular weight compounds (monomers).
But in this case, the monomers contain two or more functional groups, which lose their atoms during the reaction, from which other substances are formed (water, ammonia, hydrogen halides, etc.).
Thus, the composition of the elementary unit of the polymer differs from the composition of the initial monomer, and in the course of the polycondensation reaction, we obtain not only the polymer itself, but also other substances.
An example of a polycondensation reaction is the formation capron from aminocaproic acid:
During this reaction, the amino group ( -NH2) loses one hydrogen atom, and the carboxyl group ( -COOH) loses its hydroxyl group ( -HE). The ions separated from the monomers form a water molecule.
natural polymers
Examples of natural macromolecular compounds (polymers) are polysaccharides starch and cellulose, built from elementary units, which are monosaccharide residues ( glucose).
Leather, wool, cotton, silk are all natural polymers.
Starch formed as a result of photosynthesis, in the leaves of plants, and stored in tubers, roots, grains.
Starch- a white (granular under a microscope) powder, insoluble in cold water, in hot water it swells, forming a colloidal solution (starch paste).
Starch is a mixture of two polysaccharides built from amylose (10-20%) and amylopectin (80-90%).
Glycogen
Glycogen - a polymer based on the maltose monomer.
In animal organisms, glycogen is a structural and functional analogue of vegetable starch.
Glycogen is the main storage form of glucose in animal cells.
Glycogen forms an energy reserve that can be quickly mobilized if necessary to make up for a sudden lack of glucose.
In structure, glycogen is similar to amylopectin, but has even more chain branching.
(or fiber) is the most common plant polysaccharide. It has great mechanical strength and acts as a supporting material for plants.
The purest natural cellulose- cotton fiber - contains 85-90% cellulose. The wood of coniferous trees contains about 50% cellulose.
Squirrels- polymers, the elementary units of which are amino acid residues.
Tens, hundreds and thousands of amino acid molecules that form giant protein molecules combine with each other, releasing water at the expense of carboxyl and amino groups. The structure of such a molecule can be represented as follows:
Squirrels- natural high-molecular nitrogen-containing organic compounds. They play a primary role in all life processes, they are carriers of life. Proteins are found in all tissues of organisms, in the blood, in the bones.
Squirrels found in all tissues of organisms, in the blood, in the bones. Enzymes (enzymes), many hormones are complex proteins.
Protein, as well as carbohydrates and fats, are the most important essential part of food.
natural rubber
Natural (natural) rubber– monomer-based polymer isoprene.
Natural rubber found in the milky juice of rubber plants, mainly tropical (for example, the Brazilian Hevea tree).
Another natural product gutta-percha- is also a polymer of isoprene, but with a different molecular configuration.
Raw rubber is sticky, fragile, and with a slight decrease in temperature becomes brittle.
To give products made of rubber the necessary strength and elasticity, the rubber is subjected to vulcanization sulfur is introduced into it and then heated. Vulcanized rubber is called rubber.
Synthetic polymers
Synthetic polymers- These are a variety of materials, usually obtained from cheap and affordable raw materials. On their basis, plastic masses (plastics), artificial and synthetic fibers, etc. are obtained.
plastics- complex compositions into which various fillers and additives are introduced, which give the polymers the necessary set of technical properties.
Polymers and plastics based on them, are valuable substitutes for many natural materials (metal, wood, leather, adhesives, etc.).
Synthetic fibers successfully replace natural ones - silk, woolen, cotton.
At the same time, it is important to emphasize that, in a number of properties, materials based on synthetic polymers are often superior to natural ones. It is possible to obtain plastics, fibers and other compounds with a set of specified technical properties. This makes it possible to solve many problems of modern technology that could not be solved using only natural materials.
polymerization resins
Polymerization resins include polymers obtained by the polymerization reaction of predominantly ethylene hydrocarbons or their derivatives.
Examples of polymerization resins: polyethylene, polypropylene, polystyrene, polyvinyl chloride, etc.
Polyethylene.
Polyethylene is a polymer formed during the polymerization of ethylene.
Or in short:
Polyethylene- a saturated hydrocarbon with a molecular weight of 10,000 to 400,000. It is colorless translucent in thin layers and white in thick layers. Polyethylene- waxy, but solid material with a melting point of 110-125 degrees C. It has high chemical resistance and water resistance, low gas permeability.
It is used as an electrical insulating material, as well as for the manufacture of films used as packaging material, dishes, hoses, etc.
The properties of polyethylene depend on the method of its production. High density polyethylene has a lower density and lower molecular weight (10000-45000) than low-pressure polyethylene(molecular weight 70000-400000), which affects the technical properties.
For contact with food products, only high-pressure polyethylene is allowed, since low-pressure polyethylene may contain catalyst residues - compounds of heavy metals that are harmful to human health.
Polypropylene.
Polypropylene is a polymer of propylene, a homologue of unsaturated ethylene hydrocarbons following ethylene.
In appearance, it is a rubber-like mass, more or less hard and elastic.
Differs from polyethylene in higher melting point.
Polypropylene used for electrical insulation, for the manufacture of protective films, hose pipes, gears, instrument parts, high-strength and chemically resistant fibers. The latter is used in the production of ropes, fishing nets, etc.
Films from polypropylene much more transparent and stronger than polyethylene. Food products in polypropylene packaging can be subjected to heat treatment (boiling and heating, etc.).
Polystyrene
Polystyrene formed during the polymerization of styrene:
It can be obtained in the form of a transparent glassy mass.
It is used as organic glass, for the manufacture of industrial goods (buttons, combs, etc.).
artificial rubber
The absence of natural rubber in our country necessitated the development of an artificial method for obtaining this most important material. Soviet chemists found and for the first time in the world implemented (1928-1930) on an industrial scale a method for producing synthetic rubber.
The starting material for the production of synthetic rubber is an unsaturated hydrocarbon butadiene or divinyl, which polymerizes like isoprene.
The original butadiene is obtained from ethyl alcohol or butane, associated petroleum gas.
Condensation resins
To condensation resins include polymers obtained by a polycondensation reaction. For example:
- phenol-formaldehyde resins,
- polyester resin,
- polyamide resins, etc.
Phenol-formaldehyde resins
These macromolecular compounds are formed as a result of the interaction of phenol ( C 6 H 5 OH) with formaldehyde ( CH 2 \u003d O) in the presence of acids or alkalis as catalysts.
Phenol-formaldehyde resins have a remarkable property: when heated, they first soften, and when heated further, they harden.
Valuable plastics are made from these resins - phenol plastics. Resins are mixed with various fillers (wood flour, shredded paper, asbestos, graphite, etc.), with plasticizers, dyes, and various products are made from the resulting mass by hot pressing.
Polyester resins
An example of such resins is the polycondensation product of a dibasic aromatic terephthalic acid with dihydric alcohol ethylene glycol.
The result is polyethylene terephthalate- a polymer in the molecules of which the grouping of an ester is repeated many times.
In our country, this resin is produced under the name lavsan(abroad - terylene, dacron).
It is used to make a fiber that resembles wool, but is much stronger, giving indelible fabrics.
Lavsan possesses high thermal, moisture, and svtostoykost, is steady against action of alkalis, acids and oxidizers.
Polyamide resins
Polymers of this type are synthetic analogs of proteins. In their chains there are the same as in proteins, repeatedly repeating amide –CO–NH– groups. In the chains of protein molecules, they are separated by a link from one FROM-atom, in synthetic polyamides - a chain of four or more FROM-atoms.
Fibers obtained from synthetic resins - capron, enant and anid- in some properties they significantly exceed natural silk.
They produce beautiful, durable fabrics and knitwear. In the technique, ropes made of nylon or anid are used, ropes that are characterized by high strength. These polymers are also used as the basis for car tires, for the manufacture of nets, and various technical products.
Kapron is a polycondensate aminocaproic acid containing a chain of six carbon atoms:
Enant- aminoenanthic acid polycondensate containing a chain of seven carbon atoms.
Anid (nylon and perlon) is obtained by polycondensation of dibasic adipic acid HOOS-(CH 2) 4 -COOH and hexamethylenediamine NH 2 - (CH 2) 6 - NH 2.
5.3. POLYCONDENSATION
Polycondensation is a reaction of the formation of macromolecules when monomers are combined with each other, accompanied by the elimination of simple substances - water, alcohol, ammonia, hydrogen chloride, etc. During polycondensation, a number of kinetically unrelated bimolecular reactions take place. Features of the polycondensation reaction:
- 1) the elemental composition of the polymer unit differs from the composition of the initial monomer;
- 2) monomeric units in a polymer molecule are interconnected by a covalent or semipolar bond;
- 3) as a result of the reaction, polymer chains of various lengths are formed, i.e. the product is polydisperse;
- 4) polycondensation is a stepwise process.
Table 5.4. Types of compounds formed during polycondensation, depending on the nature of the functional groups
| First functional group (a) | Second functional group (b) | starting material | Type of compound formed |
| -H | H- | Hydrocarbon | polyhydrocarbon |
| -H | Cl- | halogen derivative | Also |
| -Вr | Br- | dihalogen derivative | " |
| -HE | BUT- | polyhydric alcohol | Polyester |
| -OH | HOOC- | Hydroxy acid | Polyester |
| -OH | ROOC- | Hydroxy ester | Also |
| -NH2 | NOOS- | Amino acid | Polyamide |
| -NH2 | ROOC- | Amino acid ester | Also |
| -NH2 | СlOC- | amino acid chloride | " |
Both homogeneous and heterogeneous molecules can participate in the polycondensation process. In general, these reactions are depicted by the following schemes:
- X a-A-b → a-(A) X-b+( X- 1)ab;
- X a-a-a + x b-B-b → a-(A-B)-b + 2( X- 1)ab,
where a and b are functional groups.
The properties of the product formed during polycondensation are determined by the functionality of the monomer, i.e. the number of reactive functional groups. The polycondensation reaction can be used to synthesize various classes of both carbon chain and heterochain polymers.
During the polycondensation of bifunctional compounds, linear polymers are formed (Table 5.4). If the functionality of the monomer is greater than two, then branched and three-dimensional polymers are formed. The number of functional groups in the macromolecule increases as the reaction deepens. Bifunctional compounds are of the greatest interest for the synthesis of fiber-forming polymers.
Depending on the nature of the functional groups and the structure of the resulting polymer, various classes of chemical reactions can be represented in the polycondensation reaction: polyesterification, polyanhydridation, polyamidation, etc. In table. 5.5 shows examples of different types of compounds formed during polycondensation.
The interaction of the functional groups of the monomer can lead to the formation of a polymer or low molecular weight products of a cyclic structure. For example, γ-aminobutyric
Table 5.5. Functional groups and types of compounds formed during polycondensation
Table 5.5. (continuation)
Table 5.5. (ending)
the acid is incapable of polycondensation due to the formation of a stable five-membered cycle - lactam:
However, ζ-aminoenanthic acid forms a linear polymer as a result of dehydration:
Increasing the distance between the functional groups increases the likelihood of the formation of macromolecules. Cyclization as the main direction of the reaction occurs only in those cases when low strained five- and six-membered cycles should be formed.
Question. Glycine (aminoacetic acid) is incapable of condensation under normal conditions. Explain the likely cause of this phenomenon.
Answer. When two glycine molecules interact, an unstrained six-membered diketipiperazine ring is obtained according to the scheme
In this case, under normal conditions of synthesis, the polymer is not formed.
Depending on the structure of the starting materials and the method of carrying out the reaction, two variants of polycondensation processes are possible: equilibrium and nonequilibrium polycondensation.
Equilibrium polycondensation is such a process of polymer synthesis, which is characterized by small values of the rate constants and the reversible nature of transformations. Polycondensation is a multi-stage process, each stage of which is an elementary reaction of the interaction of functional groups. It is generally accepted as a postulate that the reactivity of the terminal functional groups does not change with the growth of the polymer chain. The process of equilibrium polycondensation is a complex system of reactions of exchange, synthesis and destruction, which is called polycondensation equilibrium. In general, polycondensation reactions can be represented as reactions of functional groups, for example:
~COOH + HO~ ~COO~ + H 2 O.
Accordingly, the equilibrium constant is expressed as follows:
K n p=
Meaning To P p is constant at all stages of polycondensation, i.e. does not depend on the degree of polymerization. So, for the synthesis of polyethylene terephthalate at 280°C To P p = 4.9, and polyhexamethylene adipamide at 260°C To P p = 305.
Factors affecting the molecular weight and polydispersity of polycondensation polymers. The overall rate of the polycondensation process can be estimated by determining the number of functional groups in samples taken from the reaction mixture at various time intervals. The result is expressed by the degree of completion of the reaction X m, which is defined as the proportion of functional groups that have reacted by the time of sampling.
If a N 0 - initial number of functional groups of the same type, a N t- number of groups that have not reacted at the time of sampling t, then
A task. Calculate the degree of completion of the polycondensation reactions of 8-aminocaproic acid if the initial content of carboxyl groups was N 0 \u003d 8.5 10 -3 eq / g, and the final - N t= 2.4 10 -4 equiv/g.
Solution. The reaction scheme is as follows:
By formula (5.56) we find that X m = 0.971.
To obtain polymers with a maximum molecular weight, monomers are taken in strictly equivalent amounts. Each functional group of one starting substance can react with a functional group of another starting substance during polycondensation.
However, the reaction for the synthesis of polyamides or polyesters is usually catalyzed by H + . The process of protonation of the reactive carboxyl group can be carried out at the expense of the second HOOC- group. Therefore, the reaction rate between a diamine and a diacid or a diol and a diacid can be described respectively as
- -DC/dt = K n;
- -DC/dt = K n[COOH][COOH][OH].
Under the condition of equivalence of the reacting functional groups and taking into account that = [OH] = [HOOS] = FROM, we have
where FROM- concentration of functional groups; K p is the reaction rate constant.
After integration with t= 0 and FROM = FROM 0 we have
A task. Calculate the rate constant of the polycondensation reaction of sebacic acid ( M 0 = 202) and 2,5-toluenediamine ( M 0 = 122) if after 40 min of reaction at 260°C the concentration of carboxyl groups was N t= 1.7 10 -4 equiv/g.
Solution. The reaction scheme is as follows:
n NOOS(CH 2) 6 COOH + n H 2 NC 6 H 3 (CH 3) NH 2 HO n H+2( n- 1) H 2 O.
We calculate the initial concentration of carboxyl groups in the initial mixture, taking into account that 2 moles of monomers participate in the reaction:
FROM 0 \u003d 2 / (202 + 122) \u003d 0.61 10 -3 eq / g.
According to the formula (5.58) we determine the reaction rate constant:
Whereas there is no significant volume of the system when the water is removed [i.e. it can be considered that C t = C 0 (1 - X m)], we have
A task. Determine the rate constant of the polycondensation reaction of adipic acid and ethylene glycol K p and find out whether it changes with an increase in the size of the molecules of the reacting substances, if the substances are taken in equivalent
Rice. 5.7. Dependency (1 - X m) -2 of the duration of polycondensation t
quantities and obtained the following values of the degree of completeness of the reaction at certain intervals:
| t, min | 20 | 40 | 60 | 120 | 180 |
| X m | 0,90 | 0,95 | 0,96 | 0,98 | 0,99 |
Solution. According to equation (5.59), if K p does not change with the size of the reacting molecules, then the dependence 1/(1 - X m) 2 = f(t) must be linear. We build a dependency graph (Fig. 5.7), having previously calculated the values 1/(1 - X m) 2:
100; 400; 625; 2500; 1000.
A linear dependence (see Fig. 5.7) is observed only with small degrees of completion of the reaction. The reaction scheme is as follows:
According to equation (5.59) we calculate K p for t= 40 min:
\u003d 5.4 10 4.The total rate of the polycondensation process can be described by the equation
where K p is the rate constant of the polycondensation reaction; X m - the proportion of the functional groups of the monomer that reacted during the time t; a- the amount of low molecular weight product formed during the time t; To P p is the polycondensation equilibrium constant.
In order for the polycondensation reaction to be directed towards the formation of a polymer, the amount of a low molecular weight product in the reaction mixture must be less
A task. Determine the constant of the polycondensation equilibrium "polycondensation - hydrolysis", if during the polycondensation of benzidine and suberic acid in 30 minutes the proportion of carboxyl groups that entered into the reaction was 0.84; water content in the system - 0.1 10 -3 mol/g; K n = 400; V= 1.3 10 -2 mol/(g min).
Solution. The reaction scheme is as follows:
n H 2 N (C 6 H 4) 2 NH 2 + n HOEP(CH 2) 6 COOH H n OH+ n H2O.
K n p=
\u003d 3.3 10 -3.The average degree of polymerization of the polycondensation product depends on the content of the low molecular weight reaction product, changing in accordance with the polycondensation equilibrium equation, similarly to (6.49). But
where n a- molar fraction of a low molecular weight product released during polycondensation.
A task. Determine the maximum allowable residual amount of ethylene glycol dg in% (wt.) in the polycondensation reaction of diethylene glycol terephthalate in the process of obtaining a polymer with a molecular weight of 20,000, if To P p = 4.9.
Solution. The reaction scheme is as follows:
R p = 20000/192 = 104.
By formula (5.61) we find n a:
n a = To n p/ R 2 \u003d 4.9 / 104 2 \u003d 4.5 10 -4 mol / mol,
X\u003d 4.5 10 -4 62 100/192 \u003d 0.008% (wt.).
A task. Calculate the number average and weight average molecular weights of the polymer obtained from the polycondensation of 4-amino-2-chloroethylbenzene if the degree of completion of the reaction was 99.35%. Assess the polydispersity of the reaction product.
Solution. It is easy to show that
where X m is the degree of completion of the reaction; M 0 is the molecular weight of the monomer unit.
The reaction scheme is as follows:
In accordance with equation (1.70)
U = Mw/M n - 1 = 1,0.
If a N 0 is the initial number of functional groups of the same type, then the degree of completion of the polycondensation reaction can be expressed as follows:
Solution. The scheme of the polycondensation reaction is as follows:
We find X m according to equation (5.64):
X m = 0.0054 436 30/(2 + 0.0054 436 30) = 0.971.
To calculate the fractional composition of the polycondensation products of linear bifunctional compounds, one can use the Flory equation in the first approximation
where Wp- mass fraction of the polymer fraction with the degree of polymerization P n.
On fig. 5.8 shows differential MWD curves characterizing the polydispersity of polycondensation products at various degrees of completion of the reaction X m. Obviously, as the degree of conversion of the initial polymers increases, the degree of polydispersity increases.
However, as a result of reactions that promote the establishment of polycondensation equilibrium, in many cases the MWD, even at high degrees of conversion, is characterized by relatively small values U(U
Fig.5.8. Differential MWD curves calculated using the Flory equation (5.60) for various degrees of completion X m of the polycondensation reaction (numbers near the curves)
Solution. The reaction scheme for the synthesis of this polymer is as follows:
According to equation (5.65) we calculate Wp:
- a) Wp= 40 0.9 40-1 (1 - 0.9) 2 = 0.065;
- b) Wp= 40 0.99 40-1 (1 - 0.99) 2 = 0.0034.
Thus, as the reaction deepens, the content of fractions with a molecular weight of 9000 decreases.
With an increase in the content of one of the types of functional groups in the reaction mixture, the molecular weight of the polymer decreases (Fig. 5.9).
An assessment of the influence of an excess of one of the types of functional groups in the reaction medium can be carried out using the Korshak non-equivalence rule. According to this rule,
where n' is the number of moles of the bifunctional compound; t' is the number of moles of a monofunctional compound.
Polycondensation processes can be carried out in a melt (if the monomers and polymer are sufficiently stable at the melting temperature of the polymer), in solution, in the solid phase, and also at the interface between two phases (immiscible liquids, liquid-solid, etc.). Under high vacuum conditions, ensuring the removal of low molecular weight reaction products, at a temperature below or above T pl it is possible to carry out the reaction of post-polycondensation (respectively in the solid or liquid phase).
This is a crystalline substance with Tmelt = 68.5 - 690 C. Let's dissolve well in water, alcohol, ether and other organic solvents. Aqueous solutions of acids cause hydrolysis to ε - ami-
nocaproic acid. When heated to 230 - 2600 C in the presence of small amounts of water, alcohol, amines, organic acids, it polymerizes to form a polyamide resin.
ly. It is a product of large-scale production.
ω-Dodecalactam (laurinlactam) is obtained by a multi-stage synthesis from 1,3-butadiene.
3CH2 |
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Laurin lactam is a crystalline substance with Tmelt = 153 - 1540 C, readily soluble in alcohol, benzene, acetone, poorly in water. When heated, it polymerizes into polyamide, however,
polymerization proceeds worse than that of ε-caprolactam. (Lauric or dodecanoic acid - CH3 (CH2) 10 COOH.)
4.2. Methods for obtaining polyamides Polyamides are usually referred to the group of polycondensation polymers, i.e. polymers,
emitted as a result of polycondensation reactions. Such an assignment is not very correct,
since polymers of this type can be obtained both by polycondensation and polymerization
zation of monomers. Polycondensation produces polyamides from ω-aminocarboxylic acids
(or their esters), as well as from dicarboxylic acids (or their esters) and diamines. The main polymerization methods are hydrolytic and catalytic polymerization of lacta-
mov ω-amino acids. The choice of method is determined by the possibilities of the raw material base and the requirements -
mi to the properties of the corresponding polyamide.
In industry, polyamides are obtained in four main ways:
Heteropolycondensation of dicarboxylic acids or their esters with organic diamines
n HOOCRCOOH + n H2 NR"NH2 |
N H2O |
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- heteropolycondensation of dicarboxylic acid chlorides with organic dia-
- homopolycondensationω-aminocarboxylic acids (amino acids) or their esters;
N H2O |
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- polymerization of amino acid lactams.
catalyst |
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n (CH2 )n |
HN(CH2)n CO |
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4.3. Polyamide labeling The polyamide labeling system is based on the production method and chemical
structure. A number of polyamides, especially aromatic ones, have their own names, established
provided by manufacturing firms.
For aliphatic polyamides after the word "polyamide" ("nylon" in foreign literature)
round) followed by one or two numbers separated by a comma (or dot). If the polyamide is synthesized from one monomer (amino acid or lactam), one number is put,
corresponding to the number of carbon atoms in the monomer. For example, polyamide obtained from
ε-caprolactam or from ε-aminocaproic acid, referred to as "polyamide 6"; a polymer from aminoenanthic acid - "polyamide 7", a polymer from aminoundecanoic acid -
"polyamide 11". In the technical literature, the word "polyamide" is often replaced by the abbreviation "PA" or the letter "P". Then the above designations are presented as "PA-6", "PA-11", "P-7". The composition of two numbers separated by a comma indicates that the polyamide is obtained by polycondensation of a diamine with a dicarboxylic acid or its derivatives.
The number (number) before the decimal point indicates the number of carbon atoms in the diamine; the number (number) after the decimal point is the number of carbon atoms in the used acid or its derivative. For example, "Polyamide 6,6" is derived from hexamethylenediamine and adipic acid; "Polyamide 6.10" -
from hexamethylenediamine and sebacic acid. Note that the comma (or period)
separating two numbers may be missing. So, the State Standard 10539 - 87
it is prescribed to designate the polyamide obtained from hexamethylenediamine and sebacic acid in poly, as in the amides "Polyamide obtained610". from aliphatic amines and aromatic acids, a linear structural element is indicated by a number showing the number of carbon atoms in a molecule
kule, and the link of acids is indicated by the initial letter of their names. For example, polyamide
derived from hexamethylenediamine and tere-phthalic acid, referred to as "Polyamide
The names of polyamide copolymers are made up of the names of individual polymers with an indication
percentage composition in brackets (in the literature there is a use of a hyphen instead of brackets). The first indicated is the polyamide, which is more in the copolymer. For example, name-
“Polyamide 6.10 / 6.6 (65:35)” or “Polyamide 6.10 / 6.6 - 65/35” mean that the copolymer co-
made of 65% polyamide 6.10 and 35% polyamide 6.6. In some cases, simplified notation is used. For example, the entry P-AK-93/7 means that the copolymer is prepared from 93% AG salt and 7% ω-caprolactam (here "A" denotes AG salt, "K" - caprolactam).
In addition to these designations standardized in Russia, in the technical and reference literature, there may be proper names of individual types and brands introduced by firms.
lyamides. For example, "Technamid", "Zytel-1147" and others.
4.4. Production of aliphatic polyamides Of the many polyamides synthesized to date, the most practical
of interest are:
Polyamide 6 (poly-ε-caproamide, polycaproamide, capron, nylon resin, nylon-6,
caprolon B, caprolite),
Polyamide 12 (poly-ω-dodecanamide),
Polyamide 6.6 (polyhexamethylene adipamide, anide, nylon 6.6),
Polyamide 6.8 (polyhexamethylenesuberinamide),
Polyamide 6.10 (polyhexamethylene sebacinamide),
Polyamides 6 and 12 are obtained in the art by polymerization of the corresponding lactams. Os-
tal polyamides are formed during the polycondensation of hexamethylenediamine and dibasic acids
4.4.1. Polymerization of lactams Polyamide 6 and polyamide 12 are predominantly obtained in this way.
4.4.1.1. Polyamide 6
Polyamide 6 or polycaproamide is obtained by polymerization of ε-caprolactam in
the absence of hydrolytic agents or catalysts that promote the opening of the lactam ring. The process of polymerization under the action of water is called hydrolytic polymerization.
tion. Catalytic (anionic or cationic) polymerization of ε-caprolactam proceeds in the presence of alkaline or acid catalysts. The main amount of PA-6 is obtained by hydrolytic polymerization of caprolactam.
Hydrolytic polymerization of ε-caprolactam flows under the action of water, sol-
ditch acids, salts or other compounds that cause hydrolysis of the lactam cycle. Education-
The reduction of polyamide proceeds in two stages. The chemistry of the process can be represented by the scheme:
H2 N(CH2 )5COOH |
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HN(CH2 )5CO |
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The first stage of the process, hydrolysis of caprolactam to aminocaproic acid, is the slowest stage of the process, which limits its overall rate. Therefore, in
In water, the polymerization of caprolactam is carried out in the presence of catalysts. These are most often the aminocaproic acid itself or the salt of AG (hexamethylene adipate, the salt of adi-
pinic acid and hexamethylenediamine - HOOC (CH2)4 COOH H2 N(CH2)6 NH2), in which the reagents are in strictly equimolecular ratios.
The macromolecule of the resulting polyamide contains free terminal carboxyl and amino groups, which is why it is prone to destructive reactions and further polycondensation.
tion when heated during processing. To obtain a more stable product, these groups can be blocked by introducing monofunctional substances into the reaction mass - alcohols, acids or amines. Such compounds, called stabilizers or regulator-
viscosities, react with end groups and thereby stabilize the polymer, limiting its ability to enter into further reactions. This ensures the possibility of
obtain a polymer with a given molecular weight and viscosity by changing the amount of stabilizer
congestion. Acetic and benzoic acids are often used as a stabilizer.
Hydrolytic polymerization is a reversible process and the equilibrium state depends on temperature. When carrying out the reaction in the temperature range of 230 - 2600 C, the content of mo-
number and oligomers in the resulting polyamide is 8 - 10%. At such temperatures, all reagents and polyamide can be actively oxidized by atmospheric oxygen. Therefore, the process is carried out in an inert atmosphere of dry nitrogen with a high degree of purification.
The polymerization process can be carried out according to periodic or continuous schemes using equipment of various designs. On fig. Figure 3 shows a scheme for the production of PA 6 by a continuous method in a column-type reactor. The technological process of folding
It consists of the stages of preparation of raw materials, polymerization of ε-caprolactam, cooling of the polymer, its grinding, washing and drying.
Preparation of raw materials consists in melting caprolactam at 90 - 1000 C in a separate apparatus
rate 3 with stirring. In apparatus 6, a 50% aqueous solution of AG salt is prepared. Prepare-
The prepared liquids are continuously supplied by dosing pumps 1 and 4 through filters 2 and 5
in the upper part of the reactor 7 (column about 6 m high with horizontal perforated
mi metal partitions that contribute to the turbulence of the flow of reagents when they move from top to bottom). The reactor is heated through jacket sections with dinil (a eutectic mixture of diphenyl and diphenyl ether). The temperature in the middle part of the column is about 2500 C,
in the lower - up to 2700 C. The pressure in the column (1.5 - 2.5 MPa) is provided by the supply of nitrogen and pa-
ramie of the resulting water.
Polymerization begins immediately after mixing the components. released during the reaction
tion and the water introduced with the AG salt evaporates. Its vapors, rising along the column, contribute to turbulence and mixing of the reaction mass and entrain caprolactam vapors with them.
Upon exiting the column, the vapor mixture sequentially enters reflux condensers 8
and 9. In the first, caprolactam is condensed, returning to the column. Condensed-
In the second, water vapor is removed for cleaning. The monomer conversion in the column is about 90%.
Caprolactam |
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for cleaning |
Rice. 3. Scheme for the production of polyamide 6 (polycaproamide) by a continuous method:
1, 4 - dosing pumps; 2, 5 - filters; 3 - caprolactam melter; 6 - apparatus for dissolving AG salt; 7 - column-reactor; 8, 9, - refrigerators; 10 - cutting machine; 11 - washer-extractor; 12 - filter; 13 - vacuum dryer; 14 - rotating watering drum.
The resulting molten polymer is squeezed out through a slotted die into the co-
the lower part of the column in the form of a tape on the cold surface of a rotating
precise water of the watering drum 14, is cooled and, with the help of guide and pull rolls, enters the cutting machine 10 for grinding.
extractor 11. The content of low molecular weight compounds after washing is less than
1.5%. The washed crumb is separated from the water on the filter 12 and dried in a vacuum dryer
13 at 125 - 1300 C up to a moisture content of not more than 0.2%.
Anionic polymerizationε-caprolactam can be carried out in solution or melt mo-
numbers at temperatures below the melting point of the polymer.
catalyst |
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n (CH2 )5 |
HN(CH2 )5CO |
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Polymerization is carried out in the presence of a catalytic system consisting of a mixture of
talizator and activator. Alkali metals and their hydroxides can serve as catalysts.
carbonates, other compounds. In technology, mainly sodium salt ε is used - capro-
lactam formed by the interaction of sodium with lactam.
(CH2)5 |
1/2 H2 |
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N-Na+ |
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This salt easily reacts with lactam to form an N-acyl derivative, which is added |
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connects to lactam, giving rise to a polyamide chain and remaining at its end until complete |
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monomer consumption. |
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(CH2)5 |
(CH2)5 |
(CH2)5 |
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N-Na+ |
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N-CO-(CH2)5 - NH |
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Activators (cocatalysts) help speed up the reaction. In their quality |
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N-acyl derivatives of lactam or compounds capable of acylating lactam are used |
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there under polymerization conditions (carboxylic acid anhydrides, esters, isocyanates, etc.). Under |
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under the influence of such a system, the polymerization of ε-caprolactam proceeds without an induction period |
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at atmospheric pressure and ends at 140 - |
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1800 C for 1 - 1.5 hours with a monomer conversion of 97 - 99%. |
Caprolactam |
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Such "soft" conditions and the speed of polymerization |
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allow it to be carried out not in reactors, but in forms, |
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having the configuration and dimensions of future products. |
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Another advantage of anionic polymerization is |
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the possibility of obtaining polyamides with uniformly distributed |
caprolactam |
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twisted spherulite structure, without shrinkage shells |
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wines, pores, cracks and other defects. |
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The method of anionic polymerization of ε-caprolactam in |
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melt in the presence of sodium salt of ε-caprolactam |
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and activator was called "high-speed polymer- |
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zation”, and the resulting polymer is named after |
In a heating cabinet |
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spilled or caprolon B. It is also used on- |
caprolite production: |
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1 - dosing pump; 2 - reactor |
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title "polyamide block" Assignment of own |
production of sodium salt of caprolactam; 3- |
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filter; 4 - melter; 5 - mixer capro |
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the name of the poly-ε- |
lactam with N-acetylcaprolactam; 6 - before- |
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zirovochny pump; 7 - mixer; 8 - form |
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caproamide is explained by the fact that caprolon B, having the same chemical structure as poly- |
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amide 6, markedly differs from it in properties. It exhibits (Table 5) higher strength |
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ness, hardness, heat resistance, has less water absorption, etc. |
This is explained, in |
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slightly larger molecular weight of caprolite, and secondly, more ordered |
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structure. Obtaining caprolon B includes (Fig. 4) |
stages of preparation of raw materials, mixed |
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components and polymerization. |
At the stage of preparation of raw materials, caprolactam is melted and |
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thoroughly dried under negative pressure in a nitrogen atmosphere in a container |
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type with stirrer 4. |
Half of this melt after filtration is mixed in the appa- |
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with the calculated amount of metallic sodium for the preparation of sodium salt |
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ε-caprolactam, and the other half - in apparatus 5 is mixed with a cocatalyst (N - ace- |
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tilcaprolactam). Both melts (solutions) with a temperature of 135 - 140 0 C are dosed by pump-
mi 1 and 6 in the required proportions into a quick mixer 7, from where the mixture enters the casting molds, the capacity of which can reach 0.4 - 0.6 m3. The filled molds are installed for 1.0 - 1.5 hours in heating cabinets for polymerization with a gradual increase
temperature from 140 to 1800 C. Then the molds with the polymer are slowly cooled to room temperature.
temperature and polymer castings are removed from them. In washing off the monomer, it is necessary -
there is no interest here, since its content does not exceed 1.5–2.5%.
High-speed polymerization of ε-caprolactam is used to obtain large-sized and thick-walled or non-standard finished products, as well as castings, products from which are prepared by mechanical processing.
4.4.1.2. Polyamide 12
Polyamide 12 (poly-ω-dodecanamide or nylon 12) is obtained in industry by methods
hydrolytic and anionic polymerization of ω-dodecalactam.
N H2O |
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Hydrolytic polymerization is carried out in the presence of water and acid (adipic,
orthophosphoric). The technology for obtaining nylon 12 by this method is similar to the technology for the synthesis of polyamide 6. The properties of polyamide 12 are shown in table 5.
The anionic polymerization of ω-dodecalactam is also similar to that of ε-caprolactam.
At lower temperatures, a polymer is formed with a higher molecular weight, a more uniformly developed spherulitic structure, and, as a result, with increased physical
mechanical properties.
4.4.2. Polycondensation of hexamethylenediamine and dicarboxylic acids Polyamides from dicarboxylic acids and diamines or from amino acids are obtained by the method
equilibrium polycondensation. For the synthesis of a polymer with a high molecular weight, it is necessary
dimo fulfill several main conditions. One of them is due to the reversibility of polycondensation reactions. Because of this, the formation of a sufficiently high molecular weight polymer
is possible only with the timely and complete removal of water, which is achieved by carrying out
process in vacuum or with continuous current through the reaction mass of dry inert gas.
In addition, it should be taken into account that as the reaction proceeds, the concentrations of reactants and the rate of the process decrease. A typical way to increase the rate of reactions is to increase the temperature. However, above 3000 C, polyamides begin to noticeably decompose.
swear. Therefore, in order to achieve sufficient conversion, it is necessary to increase the duration
the contact strength of the reagents. Thus, the molecular weight of the resulting polyamides can be controlled during their formation by the duration of the process.
In addition to temperature and time factors, to obtain a high molecular weight
Liamide requires strict equimolecularity of the reagents. An excess of one of them, even within 1%, leads to the formation of polymer chains, at the ends of which there will be
identical functional groups of the excess reagent. With an excess of diamine, the end groups will be NH2 groups, and with an excess of acid, COOH groups. This will stop the chain propagation reaction. Equimolecularity is achieved by using
lycondensation not of the acids and diamines themselves, but of their acid salts. The preparation of such salts is
It is an independent stage in the processes of polyamide synthesis by polycondensation. Used
ion for the polycondensation of salts has a number of advantages: salts are non-toxic, easily crystalline
are lysed, practically do not change, unlike diamines, properties during long-term storage
nii, do not require special storage conditions.
Ensuring the equimolecularity of the reagents should theoretically lead to
the formation of a polymer with an infinitely large molecular weight. However, in industrial practice, due to the inevitable loss of part of the reagents and the passage of side reactions, in which
functional groups can enter, the molecular weight of polymers is in the range of 10,000 - 50,000.
4.4.2.1. Polyamide 6.6
Polyamide 6.6 (polyhexamethylene adipamide, P-66, nylon 6.6, anide) is formed during poly-
condensation of hexamethylenediamine and adipic acid.
HN(CH) NHCO(CH) CO |
N H2O |
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.... .... .......... |
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... . |
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. . ... .. . ... .. .... .. |
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hot... .. .. ...... ..... . .... ............. |
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. .. ................................ . |
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..... .. |
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...... . |
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..... .... |
cold |
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Polyamide |
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Fig.5. Scheme for the production of polyhexamethylenediadimamide (polyamide 6.6):
1 - centrifuge; 2 - apparatus for separating salt from a solution; 3 - apparatus for obtaining salt; 4 - autoclave reactor; 5 - refrigerator; 6 - condensate collector; 7 - cutting machine; 8 - dryer; 9 - cooling bath
The first stage of the process is the synthesis of a salt of adipic acid and hexamethylenediami-
on (AG salts). A salt solution is formed in a heated apparatus 3 by mixing 20% me-
tanol solution of adipic acid with 50 - 60% solution of hexamethylenediamine in methanol. In apparatus 2, when the mass is cooled, the AG salt, which is poorly soluble in methanol, is released from the solution. Its crystals are separated from the mother liquid in a centrifuge 1, dried and used
used for polycondensation. Salt - white crystalline powder with Tmelt = 190 - 1910 C,
easily soluble in water, stable when stored dry and in the form of aqueous solutions.
The process of synthesizing polyamide 6,6 from AG salt is not much different from the process of polymerization
ε-caprolactam. The most significant feature is the elevated temperature of the polycone
densations. The optimum reaction rate is reached at 270 - 2800 C. In this case, the reaction proceeds almost to the end, and upon reaching equilibrium, a polymer is formed containing less than 1% of monomers and low molecular weight compounds. The molecular weight distribution is rather narrow. The reason for the absence of significant polydispersity is the side de-
structural processes taking place under the influence of temperature and low molecular weight fractions. First of all, high-molecular fractions are subjected to destruction. For more-
more active limitation of their presence in the commercial polymer, they are added to the reaction mass -
all monofunctional compounds capable of reacting with terminal groups of polyamino-
Yes. As in the synthesis of polyamide 6, such stabilizer compounds (viscosity regulators)
bones) can be acetic, benzoic acid. These compounds not only limit the molecular
the molecular mass of the polymer during its formation, but also contribute to the constancy of the viscosity of the
polymer melt during its processing, i.e. upon remelting, which may cause further polycondensation.
Polycondensation is carried out in an autoclave at a pressure of 1.5 - 1.9 MPa in a nitrogen atmosphere.
Autoclave 4 is loaded with AG salt, the addition of acetic acid (0.1 - 0.2 mol per mol of salt) and
the apparatus through the shirt is heated with dinil to 2200 C. Further, for 1.5 - 2 hours, the dark
The temperature gradually rises to 270 - 2800 C. Then the pressure decreases to atmospheric pressure and after a short exposure rises again. Such pressure changes are repeated
a few times. With a decrease in pressure, the water formed during polycondensation boils
melts and its vapors additionally mix the polymer melt. The water vapor leaving the autoclave is condensed in the refrigerator 5, collected in the collector 6 and discharged into the purification systems.
sewage drains. At the end of the process (6 - 8 hours), the remaining water is removed under vacuum,
and the polyamide melt from the apparatus through the spinneret is squeezed out in the form of a tape into the bath 9 with
4.4.2.2. Polyamides 6.8 and 6.10
These polyamides are obtained by polycondensation of hexamethylenediamine and the corresponding ki-
slot (suberic and sebacic) using technologies similar to the production technology of
diamide 6.6.
Acids and diamine are introduced into the reaction in the form of their salts.
Of these polyamides, only polyamide 610 is of practical interest so far,
since the production of suberic acid is limited by its complexity.
The properties of polyamides 6.8 and 6.10 are shown in table 5.
Mixed polyamides are produced in a similar way when various components are introduced into the polycondensation, for example, salts of AG and caprolactam, salts of AG, SG and caprolac-
4.4.3. Polycondensation of diamines and dicarboxylic acid chlorides
This method has not been widely used in the industry for aliphatic polyamides due to the increased cost of carboxylic acid chlorides. However,
it is the only one for the synthesis of most aromatic polyamides, in particular phenylone and Kevlar.
4.5. Properties and applications of aliphatic polyamides Aliphatic polyamides are hard, horn-like products from white to light cream.
movable color, melting in a narrow temperature range (table 5). Narrow intervals
melting point values indicate a low polydispersity and a high concentration
Tractions in polymers of the crystalline phase. Its content can reach 60 - 80% and depends
sieves on the structure of macromolecules. Regular alifati-
cal homopolyamides, a distinctive feature of which is the content in the macro-
molecule of radicals of only one acid and one diamine. These are, for example, polyamide 6,
polyamide 6.6, polyamide 6.10. The degree of crystallinity of the material in products is affected by the conditions
depending on its processing, heat treatment mode, moisture content and special additives. Ste-
the stump of crystallinity of mixed (obtained from two or more monomers) polyamides is less. They are less durable, but have increased elasticity, transparent.
The high melting points of polyamides are explained by strong hydrogen bonds between macromolecules. The number of these bonds directly depends on the number of amide groups in the macromolecule and, therefore, is inversely related to the number of methylene groups. Hydrogen bonds determine to a large extent all other properties. From-
here: the ratio of methylene and amide groups affects both solubility and water resistance
bone, and on physical and mechanical, and on other indicators.
HOOC–CH 2 –NH 2 + HOOC–CH–NH 2 HOOC–CH 2 –NH–CO–CH–NH 2
CH 3 -H 2 O CH 3
glycine alanine glycylalanine peptide bond
(gli-ala)
Di-, tri-, .... polypeptides are called by the name of the amino acids that make up the polypeptide, in which all incoming amino acids as radicals end in - silt, and the last amino acid sounds unchanged in the name.
Resin is obtained by polycondensation of ε - aminocaproic acid or polymerization of caprolactam (lactam ε - caproic acid) capron:
N CH 2 CH 2 [- NH - (CH 2) 5 - CO - NH - (CH 2) 5 - CO -] m
caprolactam polycaprolactam (kapron)
This resin is used in the production of synthetic nylon fibers.
Another example of a synthetic fiber is enant.
Enanth is a polyamide of enanthic acid. The enant is obtained by polycondensation of 7-aminoheptanoic acid, which is in the reaction in the form of an internal salt:
N N + H 3 - (CH 2) 6 - COO - [ - NH - (CH 2) 6 - CO -] n + n H 2 O
Enanth is used for the manufacture of synthetic fiber, in the production of "artificial" fur, leather, plastics, etc. Enanth fibers are characterized by high strength, lightness and elasticity.
Tests for self-control of knowledge on the topic: "Amino acids"
1. Name the compound according to the systematic nomenclature
CH 3 - CH - COOH
A) 2-aminopropanoic acid
B) a-aminopropionic acid
C) a-alanine
D) 2-aminopropionic acid
2. Name the compound according to historical nomenclature
CH 3 - CH - CH - COOH
A) a-amino - b- methylbutyric acid
B) a-methyl - b- aminobutyric acid
C) 2-amino-3-methylbutanoic acid
D) 2-methyl - 3 - aminobutanoic acid
3. Alanine H NH 2 belongs to the series
4. The reaction products are
CH 2 - COOH PCl 5 B
NH2 NH3 C
A) A: CH 2 - COONa; B: CH 2 - COCl; C: CH 2 - CONH 2
B) A: CH 2 - COONa; B: CH 2 - COCl 2; C: CH 2 - CONH 4
C) A: CH 2 - COONa; B: CH 2 - COOH; C:CH-NH2
D) A: CH 2 - COONa; B: CH 2 - COOH; C: CH 2 - CONH 2
NH 2 N + H 3 Cl - NH 2
5. The reaction products are
CH 2 - COOH CH 3 Br B
NH2 CH3COCl C
HNO 2 D
A) A: CH 2 - COOH; B: CH 2 - COOH; C:CH2-COOH; D: CH 2 - COOH
N + H 3 Cl - NHCH 3 NH - COCH 3 OH
B) A: CH 2 - COOCl; B:CH2-COOCH3; C:CH2-COOH; D: CH 2 - COOH
NH 2 NH 2 NH-COCH 3 ; Oh
C) A: CH 2 - COCl 2; B: CH 2 - COOH; C:CH2-COOH; D: CH 2 - COOH
NH 2 NH-CH 3 NH - COCH 3 NH-N \u003d O
D) A: CH 2 - COCl 2; B: CH2—COBr; C:CH2-COOH; D: CH 2 - COOH
NH 2 NH 2 NH - COCH 3 OH
6. a-Amino acids form when heated
A) lactams
B) ketopiperazines
C) lactones
D) lactides
7. b-amino acids form when heated
A) unsaturated acids
B) ketopiperazines
C) lactams
D) lactones
8. g-amino acids form when heated
A) lactams
B) unsaturated acids
C) lactides
D) lactones
9. During the polycondensation of amino acids,
A) peptides
C) piperazines
D) polyenes
10. Peptide bond in protein molecules is
11. Polycondensation differs from polymerization:
A) No formation of by-products of low molecular weight
B) Formation of by-products of low molecular weight
C) Oxidation
D) Decay
12. A qualitative reaction to a-amino acids is reaction c:
A) ninhydrin
B) a-naphthol
13. The reaction products in the Strecker-Zelinsky synthesis are named:
CH 3 HCN NH 3 2 HOH (HCl)
CH = O A B C
A) A-α-oxynitrile butyric acid; B- α-aminonitrile of butyric acid; C-
D, L -alanine;
B) A-α-oxynitrile propionic acid; B-α-aminonitrile of aminopropionic acid; C-D, L-alanine;
C) A-α-hydroxynitrile of valeric acid; B-α-aminonitrile of valeric acid;
C-D, L - threonine;
D) A-α-oxynitrile propionic acid; B-α-aminonitrile of propionic acid; C-
D, L - alanine.
14. Name the substances in the chain of transformations:
COOC 2 H 5 O \u003d N-OH [H] (CH 3 CO) 2 O C 2 H 5 ONa
CH 2 - H2O AND - H2O AT - CH3COOH FROM - C2H5OH D
malonic ether
Cl-CH 2 -CH (CH 3) 2 H 2 O (HCl) t 0
–NaCl E - CH3COOH, AND - CO2 Z
–2C2H5OH
A) A-nitrosomalon ester; B - oximmalonic ester; C-N-acetyloxymalonic ester; D-Na-N-acetyloxymalonic ester; E-isobutyl-N-acetyloxymalonic ester; G-isobutyloximmalonic ether; 3-isoleucine;
C) A-nitrosomalon ester; B - iminomalonic ether; C-N-acetyliminomalone ester; D-Na-N-acetyliminomalone ester; E-isobutyl-N-acetyliminomalone ester; G-isobutyliminomalonic ether; 3-threonine;
C) A-nitrosomalon ester; B-aminomalonic ether; C-N-acetylaminomalon ester; D-Na-N-acetylaminomalon ester; E-isobutyl-N-acetylaminomalon ester; G- isobutylaminomalone ether; Z-leucine;
D) A-oximmalonic ester; B - nitrosomalon ether; C-N-acetylnitrosomalon ester; D-Na-N-acetylnitrosomalon ester; E-isobutyl-N-acetylnitrosomalon ether; G-isobutylnitrosomalon ether; Z-valine.
CARBOHYDRATES
Carbohydrates are a large group of organic substances widely distributed in nature. These are glucose, sucrose, starch, cellulose and so on.
Every year, plants on our planet create a huge mass of carbohydrates, which is estimated at a carbon content of 4 * 10 10 tons. About 80% of the dry matter of plants is carbohydrates and 20-30% is animal organisms.
The term "carbohydrates" was proposed in 1844 by K. Schmidt, since most of these substances correspond to the formula C n (H 2 O) m. For example, a glucose molecule has the formula C 6 H 12 O 6 and is equal to 6 carbon atoms and 6 water molecules. Later, carbohydrates were found that did not correspond to this composition, for example, deoxyhexose (C 6 H 10 O 5), but the term has survived to this day.
Carbohydrates are divided into two large groups - these are simple carbohydrates or monosaccharides (monoses), substances that do not undergo hydrolysis, for example, glucose, fructose. In nature, pentoses and hexoses are more common. The second group is complex carbohydrates, which, when hydrolyzed, give monosaccharides. Complex carbohydrates, in turn, are divided into oligosaccharides and polysaccharides. Oligosaccharides consist of two to ten monose residues. "Oligos" means "few" in translation. The simplest oligosaccharides are disaccharides (bioses), consisting of two monose residues. For example, sucrose C 6 H 12 O 6 consists of residues of two monoses: glucose and fructose. Oligosaccharides consisting of residues of three monoses are called trioses, those of four are called tetraoses, and so on. Polysaccharides (polyoses) are formed from monoses as a result of their polycondensation. That is, polyoses are heterochain polymers or biopolymers, the monomers of which are monoses. Heterochain polymers contain in their chain not only carbon atoms, but also oxygen atoms, for example:
NC 6 H 12 O 6 (C 6 H 10 O 5) n + (n-1) H 2 O or (-C 6 H 10 O 4 - O -) n
Carbohydrates
Task 433
What compounds are called amines? Draw a scheme for the polycondensation of adipic acid and hexamethylenediamine. Name the resulting polymer.
Solution:
Amines are called derivatives of hydrocarbons, formed by substitution in the last hydrogen atoms for groups -NH 2 , -NHR or -NR"
:
Depending on the number of hydrogen atoms at the nitrogen atom, substituted by radicals ( R ), amines are called primary, secondary or tertiary.
Group -NH2 , which is part of the primary amines, is called the amino group. group of atoms >NH in secondary amines is called imino group.
Polycondensation scheme adipic acid and hexamethylenediamine:
Anid (nylon) is the product of polycondensation of adipic acid and hexamethylenediamine.
Task 442
What compounds are called amino acids? Write the formula for the simplest amino acid. Draw a scheme for the polycondensation of aminocaproic acid. What is the resulting polymer called?
Solution:
Amino acids compounds are called, the molecule of which contains both amine(-NH2) and carboxyl groups(-COOH). Their simplest representative is aminoacetic acid (glycine): NH2-CH2-COOH.
Aminocaproic acid polycondensation scheme:
The polycondensation product of aminocaproic acid is called capron (perlon). From capron get fibers that are stronger than natural fibers. These fibers are used in the production of clothing, car and aircraft tire cords, for the manufacture of durable and non-rotting fishing nets and gear, rope products, etc.
