chemistry lesson

Polymers — high-molecular compounds - structure of MATTER - LESSON PLANS for CHEMISTRY 11 class - lesson plans-lesson plans-author's lessons-plan-lesson summary - chemistry

The objectives of the lesson: to consolidate knowledge of the structure, composition, properties, methods of obtaining, classification of IUD, the ability to compose IUD synthesis reactions; to give an idea of the composition, synthesis, properties of the most important organic and inorganic IUD.

Basic concepts: polymer, monomer, structural unit, degree of polymerization, shape of macromolecules: linear, branched, spatial, stereoregular polymers, polymerization reaction, polycondensation reaction, thermoplasticity, thermoreactivity.

Equipment: plastic collection and tables: structure of protein, DNA; alcohol lamp, matches, a spoon for burning substances (for demonstrating experiments).

Lesson progress

I. Organizational moment

The teacher sets goals and tasks for the lesson. The main task of the lesson is to consolidate the students ' ability to characterize a compound based on the theory of the structure of compounds. Checking your homework. Elucidating the specifics of the structure, preparation, application, and classification of compounds that surround us in everyday life — plastics and fibers, based on high-molecular compounds.

II. Checking students ' knowledge

It is necessary to conduct an oral survey of the answers to questions # 1, 2, 3 of § 9 (according to the plan-the summary of the previous lesson).

§ 9. No. 1. General premises.

1) Accumulation of factual material:

a) at the time of the discovery of the Periodic law, 63 elements were known.

By the time of the creation of the TCS by a.m. Butlerov, hundreds of thousands of organic compounds were known, consisting mainly of carbon, hydrogen, oxygen, less often nitrogen, phosphorus, and sulfur.

b) there Were many works of predecessors - both on the classification of inorganic substances, and on the classification of organic substances;

C) the Congress of chemists in Karlsruhe, when the atomic and molecular doctrine was finally established, the first unified definitions of the concepts "molecule" and "atom" were adopted, as well as of atomic weight, which we now call relative atomic mass;

d) important personal qualities of scientists: Russian mentality, patriotism, encyclopedic chemical knowledge, ability to analyze and summarize facts.

2) the General direction of their development: from simple to complex.

Periodic law:

relative atomic mass → charge of the nucleus → the change of the external energy level.

Technical characteristics:

the order of connection of atoms → chemical composition → the spatial structure → electron structure.

3) Prognosticality in statements: D. I. Mendeleev predicts, describes and indicates the ways of discovering yet unknown elements. Creating a prediction theory that has proven itself in practice! There was not only the discovery of new elements, but also the synthesis of new chemical elements (a group of scientists in Dubna under the leadership of academician Flerov synthesized 118 element, possibly will have the name " Moscovite»),

A. M. Butlerov predicts isomerism and explains the ego phenomenon. It performs many syntheses by itself. Currently, there is a synthesis of substances with predetermined properties, as well as the synthesis of IUDs that would replace natural proteins, carbohydrates, etc.

§ 9. no. 2. THC is universal, it has given an explanation of many phenomena. which are described by taking into account the Periodic law, the Periodic system. Ths seems to have forestalled the Periodic law, the system. They have a lot of things in common.

§ 9. No. 3. the Phenomenon of isomerism of inorganic compounds.

Mutual influence of atoms in molecules of inorganic compounds:

Sulfur has a radius of the atom greater than the radius of the oxygen atom, it attracts the hydrogen atom more weakly, which ensures the acidic nature of the h₂s compound.

2) the comparison of the two compounds.

  acid atanova, mesomeric and inducing effects provide the mobility of an atom in a carboxyl group.

 - chloroacetic acid.

Chloroacetic acid will be stronger, because its molecule contains a more EO atom-chlorine, which weakens the δ+ carbon # 1, so that, making up for the loss of electronic density, it attracts the electronic density of the oxygen atom more strongly, providing greater mobility of the hydrogen atom. The degree of dissociation of Chloroacetic acid is greater than the degree of dissociation of acetic acid.

3)

  amino acid aminoethanol acid.

With no. 1 S. O. +3 intermediate S. O.

C # 2 S. O. +1 redox properties.

Acid properties: the hydrogen atom in the group is mobile 

Base properties: in a group, the nitrogen atom has an unshared pair of electrons, so it shows basic properties.

The substance reacts as an acid with metals, alkalis, and salts. alcohols; as a base - with acids. The molecules interact with each other. These reactions are important in protein synthesis.

II. Learning new material

Plan of presentation

1. The definition of the CPA.

2. Classification Navy:

a) by the method of receipt:

— natural — plant and animal origin;

- chemical — artificial, synthetic;

b) by properties and application:

- plastics, elastomers, fiber.

3. Compare Navy:

a) basic structural concepts: monomer, monomer requirements;

b) a structural unit;

C) degree of polymerization, average molecular weight;

d) forms of macromolecules depending on the structure of the chain bases, stereoregularity.

e) crystalline and amorphous structure of the polymer.

4. Special properties typical for most IUD, aggregate state; melting point, ratio to solvents and aggressive media, strength, thermoplasticity, thermoset activity.

5. polymer synthesis Reactions; polymerization reaction; reaction of polyconlensation, Homo-and heteropolymerization, Homo -, hetero-and polycondensation, copolymerization, copolycondensation.

6. Some information about inorganic polymers.

7. Plan the characteristics of the polymer:

— title;

— structural link;

— monomer;

— fusion reaction;

- degree of polymerization M_r;

— macromolecule shape;

— special physical properties: crystallinity; amorphous, negative property, thermoplasticity, thermosetting;

— application;

— positive and negative qualities.

Polymers are substances with a very high molecular weight that contain a repetitive grouping of atoms.

According to the method of obtaining polymers there are:

natural — vegetable origin (cellulose, starch), animal origin (proteins, nucleic acids, natural rubber), mineral (minerals, rocks, fiber asbestos);

chemical-chemical polymers obtained by processing a natural polymer are called artificial (esters, celluloses), and chemical polymers obtained by synthesis are called synthetic (polyethylene, polypropylene, kapron).

According to their properties and application, polymers are divided into plastics, elastomers, and fibers.

What structure do polymers have? All polymers are synthesized from monomers.

A monomer is a low-molecular-weight substance from which IUD is formed as a result of synthesis.

Requirements for a monomer;

1) the presence of multiple links of one or more.

Example. H₂S=CH₂-ethylene, synthesis of polyethylene.

H₂S=SN-SN=SN-butadiene-1,3.

Synthesis of rubber.

2) the presence of such functional groups that interact with each other.

Example. "an amino acid.

Functional groups-COOP and-NH₂, are able to interact with each other. Protein and capron synthesis.

A structural link is a group of atoms that is repeated many times in the macromolecule of the IUD. The structural link is similar to the monomer in composition, but different in structure.

Example: the monomer of polyethylene H₂C=CH₂.

The structural link of polyethylene is CH₂—CH₂—.

Degree of polymerization — a number that shows the number of structural units in a macromolecule (how many monomers are connected in a macromolecule in polymers) is denoted by n, n— the value is not constant, as a rule, the average, so the molecular weight of the polymer is the average M_CP.

Example:

The geometric structure of the macromolecule — the shape of the macromolecule-depends on the structure of the main chain and can be:

a) linear: (polyethylene)

b) branched: (starch);

C) spatial (mesh, stitched): 

Example: rubber, linear macromolecules are "stitched" together with the help of sulfur atoms.

Stereoregular polymers are formed if IUD macromolecules are constructed from a structure of links of the same spatial configuration or a structure of links with different spatial configuration, but alternating in the chain with a certain frequency.

Non-stereoregular polymers are formed if structural links with different configurations alternate randomly.

Polymers can have a crystalline or amorphous structure.

The crystallinity of a polymer is understood as an ordered (parallel) arrangement of macromolecules.

Amorphous structure is characterized by the lack of ordering of macromolecules. It should be noted that the same molecules pass through the crystalline and amorphous regions of the polymer. In a polymer, an important characteristic is the degree of crystallinity.

Example: high-pressure polyethylene — 50-65%; low-pressure polyethylene-75-90%.

a-site of the polymer's crystalline structure;

b-site of the amorphous structure of the polymer.

As a rule, polymers are solid, having a certain degree of crystallinity and amorphousness, which further characterizes their properties. The IUD does not have a specific melting point.

Example: high-pressure polyethylene from 105-108 °C;

low-pressure polyethylene from 120-130°C.

At a higher temperature, the polymer is not distilled, but begins to decompose and burn. Polyethylene first softens, acquires a transparent color, then with a further increase in temperature melts, and then decomposes, burns with a blue flame, the smell of a burning candle appears, burning continues outside the flame (linear structure of polyethylene). If the polymer has a spatial structure, it immediately decomposes when heated, without passing into a viscous state, and the products of its decomposition (plastics based on phenol-formaldehyde resin) begin to burn.

Question. Why do polymers not subjected to distillation?

Answer. So that the substance melts and evaporates:

it is necessary to overcome the forces of intermolecular interaction (hydrogen bonds). Water is a low-molecular substance when ice is heated, intermolecular hydrogen bonds in crystals are destroyed, water becomes liquid, with further heating, hydrogen bonds in water associates are destroyed, it turns into a gaseous state.

In IUD, the intermolecular forces of interaction are much stronger, because unlike low-molecular substances, they are attracted to each other by a huge number of links.

When the polymer is heated, it first softens, which means that the interaction forces between some macromolecules are already weakened so that they can move relative to each other due to thermal movement. Larger macromolecules of matter interact with each other even more strongly, and to acquire such mobility they require further heating. This is the reason that polymers do not have a specific melting point. In order to carry out the distillation of a substance, it is necessary to heat it to a higher temperature. Large macromolecules would become volatile under very strong heating. But they can not stand it, chemical bonds between the atoms begin to break and the decomposition of the substance occurs before its distillation.

Most polymers are difficult to dissolve in organic solvents for the same reason. It is difficult to separate macromolecules with low-molecular-weight solvents. In polymers of linear structure, this is still possible. But if the mesh spatial structure of the IUD, then the solvent molecules can only penetrate into the polymer, which leads to its swelling (rubber). All this is due to the enormous forces of intermolecular interaction of macromolecules.

The high mechanical strength of the IUD is also explained in the same way. All polymers are inert in aggressive environments — acids, alkalis, strong oxidizers, and are also resistant to environmental influences. Polymers have a low density, they are distinguished by their lightness.

Example: low-pressure polyethylene-0.91—0.93 g/cm³, high-pressure polyethylene-0.95—0.97 g / cm³.

For proper handling of polymers, it is necessary to know the relation to heating of their macromolecules. There are thermoplastics and thermosetting polymers.

Thermoplastic polymers soften when heated and change shape easily in this state. When cooled, they solidify again, keeping the given shape. At the next heating, they soften again and can be given a new shape. Macromolecules do not change when heated.

Example: polyethylene, polypropylene, capron, etc.

Thermosetting polymers become plastic when heated, but then lose their plasticity, become non-melting, insoluble, because there is an interaction of linear macromolecules with the formation of the spatial structure of the polymer. It is no longer possible to re-process such a product.

Example: polymers based on phenol-formaldehyde resin.

Let's consider some reactions of polymer synthesis.

Polymerization reaction — the process of combining a set of monomer molecules into large molecules-macromolecules, i.e. the formation of a high-molecular compound. In the polymerization reaction, monomers with multiple bonds participate, homopolymerization is distinguished, And + A + A-monomers of one substance participate — and heteropolymerization A-B—A-B-monomers of different substances participate.

Example: homopolymerization reaction, synthesis of polyethylene:

Example: reaction of heteropolymerization (copolymerization), synthesis of styrene-butadiene rubber:

The polycondensation reaction is a chemical process of combining the initial monomer molecules in a macromolecule, resulting in the formation of a secondary low-molecular-weight substance (usually water).

Monomers for the polycondensation reaction must have functional groups interacting with each other. Distinguish the reaction of homopolymerization — synthesis of starch, nylon.

Example: the synthesis of starch.

Example: the synthesis of the polyamide from e-aminocaproic acid.

A structural unit of nylon:

Reaction just get aware, of copolycondensation.

Synthesis of phenol-formaldehyde resin, Dacron fiber.

Example: synthesis of phenol-formaldehyde resin:

Example: synthesis of Dacron fiber:

Structural link: 

An example of an inorganic polymer can be plastic sulfur S_n; the structural unit is a sulfur atom, the main purpose of the macromolecule is inorganic:

It should be concluded that the concept of polymer is universal.

Polymers are not only organic, but also inorganic. Carbon forms compounds: diamond, graphite, carbine, fullerene, and crystalline silicon. All these polymers have an atomic structure. But there is a complex of the substance with the atomic structure of polymers: silicon oxide (SiO₂) and its varieties: quartz, silica, rock crystal. Aluminosilicates are two polymers together.

It should be noted that silicon is the second most common element in nature (after oxygen) - 27.6% of the mass of the earth's crust. Its compounds: silicates, aluminosilicates-make up 75 % of the lithosphere. These include about 500 minerals, including rock-forming ones: feldspar, mica, pyroxenes (silicates): sand, clay, asbestos, talc, emerald, Topaz.

Ethylenes of the III, IV groups of the main subgroups of the II, III period B, Al, Si are most prone to the formation of inorganic polymers.

Inorganic polymers can have macromolecules in the form of Homo-and heterocycles. The macromolecules themselves are linear, branched, and reticulate.

Example: diamond, boron, mountain phosphorus, carbine (—C≡C—)_n, polycumulene (=C=C=C=)_n, plastic sulfur, polymer tin-homochainous.

More stable-heterocycle polymers, boron oxide contains fragments(silica),(aluminum oxide); carborundum SiC, polysilic acid (H₂SiO₃)_n.

Many organic element polymers are known. Based on such polymers, silicon, phosphorus, and sulfur are included in the main or side chains.

Then the teacher summarizes the presentation of the new material.

III. Homework assignment

§ 10 (before plastics), pp. 87-93. № 1 -5. Repeat proteins, nucleic acids (class 10).

IV. Consolidation

Students are encouraged to plan the characteristics of the polymer:

1. The name of the polymer.

2. Monomer, structural link. The degree of polymerization of M_SR, the degree of crystallinity (according to reference literature).

3. Form of the macromolecule.

4. Reaction synthesis.

5. Features of physical properties, positive and negative qualities.

6. Application.

Students are offered the following polymers for characterization (in the form of an assessment message): polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethylmethalkrylate (organic glass), phenol-formaldehyde resin, capron, Dacron, acetate, rubber.