Topics USE codifier: Classification chemical reactions in organic and not organic chemistry.

chemical reactions - this is a type of interaction of particles, when from some chemical substances others are obtained, differing from them in properties and structure. Substances that enter in reaction - reagents. Substances that formed during a chemical reaction products.

During a chemical reaction, chemical bonds are broken and new ones are formed.

During chemical reactions, the atoms involved in the reaction do not change. Only the order of connection of atoms in molecules changes. Thus, the number of atoms of the same substance does not change during a chemical reaction.

Chemical reactions are classified according to different criteria. Consider the main types of classification of chemical reactions.

Classification according to the number and composition of reactants

According to the composition and number of reacting substances, reactions proceeding without a change in the composition of substances are divided, and reactions occurring with a change in the composition of substances:

1. Reactions proceeding without changing the composition of substances (A → B)

For such reactions in inorganic chemistry allotropic transitions of simple substances from one modification to another can be attributed:

S rhombic → S monoclinic.

AT organic chemistry such reactions are isomerization reactions , when another isomer is obtained from one isomer under the action of a catalyst and external factors (as a rule, a structural isomer).

For example, isomerization of butane to 2-methylpropane (isobutane):

CH 3 -CH 2 -CH 2 -CH 3 → CH 3 -CH (CH 3) -CH 3.

2. Reactions occurring with a change in composition

• Coupling reactions (A + B + ... →D)- these are reactions in which one new complex substance is formed from two or more substances. AT inorganic chemistry The compound reaction includes combustion reactions of simple substances, the interaction of basic oxides with acid ones, etc. In organic chemistry such reactions are called reactions accession . Addition reactions — these are reactions in which another molecule is attached to the organic molecule in question. Addition reactions include reactions hydrogenation(interaction with hydrogen), hydration(water connection), hydrohalogenation(addition of hydrogen halide), polymerization(attachment of molecules to each other with the formation of a long chain), etc.

For example, hydration:

CH 2 \u003d CH 2 + H 2 O → CH 3 -CH 2 -OH

• Decomposition reactions (A → B+C+…) These are reactions in the course of which several less complex or simple substances are formed from one complex molecule. In this case, both simple and complex substances can be formed.

For example, when decomposing hydrogen peroxide:

2H2O2→ 2H 2 O + O 2 .

In organic chemistry separate the actual decomposition reactions and the cleavage reactions . Cleavage (elimination) reactions — these are reactions in which atoms or atomic groups are detached from the original molecule while maintaining its carbon skeleton.

For example, the reaction of hydrogen abstraction (dehydrogenation) from propane:

C 3 H 8 → C 3 H 6 + H 2

As a rule, in the name of such reactions there is a prefix "de". Decomposition reactions in organic chemistry occur, as a rule, with a break in the carbon chain.

For example, reaction butane cracking(cleavage into simpler molecules when heated or under the action of a catalyst):

C 4 H 10 → C 2 H 4 + C 2 H 6

• Substitution reactions - these are reactions in which atoms or groups of atoms of one substance are replaced by atoms or groups of atoms of another substance. In inorganic chemistry These reactions proceed according to the scheme:

AB+C=AC+B.

For example, more active halogens displace less active compounds. Interaction potassium iodide With chlorine:

2KI + Cl 2 → 2KCl + I 2 .

Both individual atoms and molecules can be replaced.

For example, when fused less volatile oxides push out more volatile from salts. Yes, non-volatile silicon oxide displaces carbon monoxide from sodium carbonate when melting:

Na 2 CO 3 + SiO 2 → Na 2 SiO 3 + CO 2

AT organic chemistry substitution reactions are reactions in which part organic molecule replaced to other particles. In this case, the substituted particle, as a rule, combines with a part of the substituent molecule.

For example, reaction methane chlorination:

CH 4 + Cl 2 → CH 3 Cl + HCl

In terms of the number of particles and the composition of the interaction products, this reaction is more similar to an exchange reaction. Nonetheless, by mechanism such a reaction is a substitution reaction.

• Exchange reactions are reactions in which two complex substances and exchange their constituent parts:

AB+CD=AC+BD

The exchange reactions are ion exchange reactions flowing in solutions; reactions illustrating the acid-base properties of substances and others.

Example exchange reactions in inorganic chemistry - neutralization of hydrochloric acid alkali:

NaOH + HCl \u003d NaCl + H 2 O

Example exchange reactions in organic chemistry — alkaline hydrolysis of chloroethane:

CH 3 -CH 2 -Cl + KOH \u003d CH 3 -CH 2 -OH + KCl

Classification of chemical reactions by changing the degree of oxidation of elements that form substances

By changing the oxidation state of elements chemical reactions are divided into oxidative reducing reactions , and the reactions going no change in oxidation states chemical elements.

• Redox reactions (ORD) are reactions in which oxidation states substances change. In doing so, there is an exchange electrons.

AT inorganic chemistry such reactions include, as a rule, reactions of decomposition, substitution, compounds, and all reactions involving simple substances. To equalize the OVR, the method is used electronic balance(the number of donated electrons must be equal to the number received) or electron-ion balance method.

AT organic chemistry separate oxidation and reduction reactions, depending on what happens to the organic molecule.

Oxidation reactions in organic chemistry are reactions in which the number of hydrogen atoms decreases or the number of oxygen atoms in the original organic molecule increases.

For example, oxidation of ethanol under the action of copper oxide:

CH 3 -CH 2 -OH + CuO → CH 3 -CH \u003d O + H 2 O + Cu

Recovery reactions in organic chemistry, these are reactions in which the number of hydrogen atoms increases or the number of oxygen atoms decreases in an organic molecule.

For example, recovery acetaldehyde hydrogen:

CH 3 -CH \u003d O + H 2 → CH 3 -CH 2 -OH

• Protolytic reactions and exchange reactions - these are reactions in which the oxidation states of atoms do not change.

For example, neutralization caustic soda nitric acid:

NaOH + HNO 3 \u003d H 2 O + NaNO 3

Classification of reactions by thermal effect

According to the thermal effect, the reactions are divided into exothermic and endothermic.

exothermic reactions are reactions accompanied by the release of energy in the form of heat (+ Q). These reactions include almost all compound reactions.

Exceptions- reaction nitrogen With oxygen with education nitric oxide (II) - endothermic:

N 2 + O 2 \u003d 2NO - Q

Gaseous reaction hydrogen with hard iodine also endothermic:

H 2 + I 2 \u003d 2HI - Q

Exothermic reactions in which light is released are called reactions. burning.

For example, combustion of methane:

CH 4 + O 2 \u003d CO 2 + H 2 O

Also exothermic are:

Endothermic reactions are the reactions that energy absorption in the form of heat ( — Q ). As a rule, most reactions proceed with the absorption of heat. decomposition(reactions requiring prolonged heating).

For example, decomposition limestone:

CaCO 3 → CaO + CO 2 - Q

Also endothermic are:

• hydrolysis reactions;
• reactions that take place only when heated;
• reactions that take place onlyat very high temperatures or under the influence of an electrical discharge.

For example, the conversion of oxygen to ozone:

3O 2 \u003d 2O 3 - Q

AT organic chemistry With the absorption of heat, decomposition reactions take place. For example, cracking pentane:

C 5 H 12 → C 3 H 6 + C 2 H 6 - Q.

Classification of chemical reactions according to the state of aggregation of reacting substances (by phase composition)

Substances can exist in three main states of aggregation − solid, liquid and gaseous. By phase state share reactions homogeneous and heterogeneous.

• Homogeneous reactions are reactions in which the reactants and products are in one phase, and the collision of the reacting particles occurs in the entire volume of the reaction mixture. Homogeneous reactions include interactions liquid-liquid and gas-gas.

For example, oxidation sour gas:

2SO 2 (g) + O 2 (g) \u003d 2SO 3 (g)

• heterogeneous reactions are reactions in which the reactants and products are in different phases. In this case, the collision of reacting particles occurs only at the phase boundary. These reactions include interactions gas-liquid, gas-solid, solid-solid, and solid-liquid.

For example, interaction carbon dioxide and calcium hydroxide:

CO 2 (g) + Ca (OH) 2 (solution) \u003d CaCO 3 (tv) + H 2 O

To classify reactions according to the phase state, it is useful to be able to determine phase states of substances. This is quite easy to do, using knowledge about the structure of matter, in particular, about.

Substances with ionic, atomic or metallic crystal lattice , usually solid under normal conditions; substances with molecular lattice, usually, liquids or gases under normal conditions.

Please note that when heated or cooled, substances can change from one phase state to another. In this case, it is necessary to focus on the conditions for conducting a particular reaction and physical properties substances.

For example, receiving synthesis gas occurs at very high temperatures, at which water - steam:

CH 4 (g) + H2O (g) \u003d CO (g) + 3H 2 (g)

So steam reforming methane — homogeneous reaction.

Classification of chemical reactions according to the participation of a catalyst

A catalyst is a substance that speeds up a reaction but is not part of the reaction products. The catalyst participates in the reaction, but is practically not consumed during the reaction. Conventionally, the scheme of the catalyst To in the interaction of substances A+B can be depicted as follows: A + K = AK; AK + B = AB + K.

Depending on the presence of a catalyst, catalytic and non-catalytic reactions are distinguished.

• catalytic reactions are reactions that take place with the participation of catalysts. For example, the decomposition of Bertolet salt: 2KClO 3 → 2KCl + 3O 2.
• Non-catalytic reactions are reactions that take place without the participation of a catalyst. For example, combustion of ethane: 2C 2 H 6 + 5O 2 = 2CO 2 + 6H 2 O.

All reactions that occur with the participation of living organisms in the cells proceed with the participation of special protein catalysts - enzymes. Such reactions are called enzymatic.

The mechanism of action and functions of catalysts are considered in more detail in a separate article.

Classification of reactions by direction

Reversible reactions - these are reactions that can proceed both in the forward and in the reverse direction, i.e. when, under given conditions, the reaction products can interact with each other. Reversible reactions include most homogeneous reactions, esterification; hydrolysis reactions; hydrogenation-dehydrogenation, hydration-dehydration; production of ammonia from simple substances, oxidation of sulfur dioxide, production of hydrogen halides (except hydrogen fluoride) and hydrogen sulfide; methanol synthesis; obtaining and decomposition of carbonates and hydrocarbonates, etc.

irreversible reactions are reactions that proceed predominantly in one direction, i.e. reaction products cannot interact with each other under given conditions. Examples are not reversible reactions: burning; explosive reactions; reactions proceeding with the formation of gas, precipitate or water in solutions; dissolution of alkali metals in water; and etc.

DEFINITION

Chemical reaction called the transformation of substances in which there is a change in their composition and (or) structure.

Most often, chemical reactions are understood as the process of transformation of initial substances (reagents) into final substances (products).

Chemical reactions are written using chemical equations containing the formulas of the starting materials and reaction products. According to the law of conservation of mass, the number of atoms of each element in the left and right parts chemical equation equally. Usually, the formulas of the starting substances are written on the left side of the equation, and the formulas of the products are written on the right. The equality of the number of atoms of each element in the left and right parts of the equation is achieved by placing integer stoichiometric coefficients in front of the formulas of substances.

Chemical equations may contain additional information about the features of the reaction: temperature, pressure, radiation, etc., which is indicated by the corresponding symbol above (or “under”) the equals sign.

All chemical reactions can be grouped into several classes, which have certain characteristics.

Classification of chemical reactions according to the number and composition of the initial and resulting substances

According to this classification, chemical reactions are divided into reactions of combination, decomposition, substitution, exchange.

As a result compound reactions from two or more (complex or simple) substances, one new substance is formed. AT general view The equation for such a chemical reaction will look like this:

For example:

CaCO 3 + CO 2 + H 2 O \u003d Ca (HCO 3) 2

SO 3 + H 2 O \u003d H 2 SO 4

2Mg + O 2 \u003d 2MgO.

2FeCl 2 + Cl 2 = 2FeCl 3

Combination reactions are in most cases exothermic, i.e. flow with the release of heat. If simple substances are involved in the reaction, then such reactions are most often redox (ORD), i.e. occur with a change in the oxidation states of the elements. It is impossible to say unequivocally whether the reaction of a compound between complex substances can be attributed to OVR.

Reactions in which several other new substances (complex or simple) are formed from one complex substance are classified as decomposition reactions. In general, the equation for a chemical decomposition reaction will look like this:

For example:

CaCO 3 CaO + CO 2 (1)

2H 2 O \u003d 2H 2 + O 2 (2)

CuSO 4 × 5H 2 O \u003d CuSO 4 + 5H 2 O (3)

Cu (OH) 2 \u003d CuO + H 2 O (4)

H 2 SiO 3 \u003d SiO 2 + H 2 O (5)

2SO 3 \u003d 2SO 2 + O 2 (6)

(NH 4) 2 Cr 2 O 7 \u003d Cr 2 O 3 + N 2 + 4H 2 O (7)

Most decomposition reactions proceed with heating (1,4,5). May be decomposed by electric current(2). The decomposition of crystalline hydrates, acids, bases and salts of oxygen-containing acids (1, 3, 4, 5, 7) proceeds without changing the oxidation states of the elements, i.e. these reactions do not apply to OVR. OVR decomposition reactions include the decomposition of oxides, acids and salts formed by elements in higher degrees oxidation (6).

Decomposition reactions are also found in organic chemistry, but under other names - cracking (8), dehydrogenation (9):

C 18 H 38 \u003d C 9 H 18 + C 9 H 20 (8)

C 4 H 10 \u003d C 4 H 6 + 2H 2 (9)

At substitution reactions a simple substance interacts with a complex one, forming a new simple and a new complex substance. In general, the equation for a chemical substitution reaction will look like this:

For example:

2Al + Fe 2 O 3 \u003d 2Fe + Al 2 O 3 (1)

Zn + 2HCl = ZnCl 2 + H 2 (2)

2KBr + Cl 2 \u003d 2KCl + Br 2 (3)

2KSlO 3 + l 2 = 2KlO 3 + Cl 2 (4)

CaCO 3 + SiO 2 \u003d CaSiO 3 + CO 2 (5)

Ca 3 (RO 4) 2 + ZSiO 2 = ZCaSiO 3 + P 2 O 5 (6)

CH 4 + Cl 2 = CH 3 Cl + Hcl (7)

Substitution reactions are mostly redox reactions (1 - 4, 7). Examples of decomposition reactions in which there is no change in oxidation states are few (5, 6).

Exchange reactions called the reactions that occur between complex substances, in which they exchange their constituent parts. Usually this term is used for reactions involving ions located in aqueous solution. In general, the equation for a chemical exchange reaction will look like this:

AB + CD = AD + CB

For example:

CuO + 2HCl \u003d CuCl 2 + H 2 O (1)

NaOH + HCl \u003d NaCl + H 2 O (2)

NaHCO 3 + HCl \u003d NaCl + H 2 O + CO 2 (3)

AgNO 3 + KBr = AgBr ↓ + KNO 3 (4)

CrCl 3 + ZNaOH = Cr(OH) 3 ↓+ ZNaCl (5)

Exchange reactions are not redox. A special case of these exchange reactions is neutralization reactions (reactions of interaction of acids with alkalis) (2). Exchange reactions proceed in the direction where at least one of the substances is removed from the reaction sphere in the form gaseous substance(3), sediment (4, 5) or low dissociating compound, most often water (1, 2).

Classification of chemical reactions according to changes in oxidation states

Depending on the change in the oxidation states of the elements that make up the reactants and reaction products, all chemical reactions are divided into redox (1, 2) and those occurring without changing the oxidation state (3, 4).

2Mg + CO 2 \u003d 2MgO + C (1)

Mg 0 - 2e \u003d Mg 2+ (reductant)

C 4+ + 4e \u003d C 0 (oxidizing agent)

FeS 2 + 8HNO 3 (conc) = Fe(NO 3) 3 + 5NO + 2H 2 SO 4 + 2H 2 O (2)

Fe 2+ -e \u003d Fe 3+ (reductant)

N 5+ + 3e \u003d N 2+ (oxidizing agent)

AgNO 3 + HCl \u003d AgCl ↓ + HNO 3 (3)

Ca(OH) 2 + H 2 SO 4 = CaSO 4 ↓ + H 2 O (4)

Classification of chemical reactions by thermal effect

Depending on whether heat (energy) is released or absorbed during the reaction, all chemical reactions are conditionally divided into exo - (1, 2) and endothermic (3), respectively. The amount of heat (energy) released or absorbed during a reaction is called the heat of the reaction. If the equation indicates the amount of released or absorbed heat, then such equations are called thermochemical.

N 2 + 3H 2 = 2NH 3 +46.2 kJ (1)

2Mg + O 2 \u003d 2MgO + 602.5 kJ (2)

N 2 + O 2 \u003d 2NO - 90.4 kJ (3)

Classification of chemical reactions according to the direction of the reaction

According to the direction of the reaction, reversible ( chemical processes, the products of which are capable of reacting with each other under the same conditions in which they are obtained, with the formation of starting substances) and irreversible (chemical processes, the products of which are not able to react with each other with the formation of starting substances).

For reversible reactions, the equation in general form is usually written as follows:

A + B ↔ AB

For example:

CH 3 COOH + C 2 H 5 OH ↔ H 3 COOS 2 H 5 + H 2 O

Examples of irreversible reactions are the following reactions:

2KSlO 3 → 2KSl + ZO 2

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

Evidence of the irreversibility of the reaction can serve as the reaction products of a gaseous substance, a precipitate or a low-dissociating compound, most often water.

Classification of chemical reactions by the presence of a catalyst

From this point of view, catalytic and non-catalytic reactions are distinguished.

A catalyst is a substance that speeds up a chemical reaction. Reactions involving catalysts are called catalytic. Some reactions are generally impossible without the presence of a catalyst:

2H 2 O 2 \u003d 2H 2 O + O 2 (MnO 2 catalyst)

Often, one of the reaction products serves as a catalyst that accelerates this reaction (autocatalytic reactions):

MeO + 2HF \u003d MeF 2 + H 2 O, where Me is a metal.

Examples of problem solving

EXAMPLE 1

Every teacher faces the problem of lack of teaching time. More precisely, it doesn’t even collide, but constantly works in conditions of its chronic lack. Moreover, over the years, the latter has been steadily increasing due to compaction. educational material, reducing the number of hours devoted to the study of chemistry, and complicating the tasks of teaching, designed to provide a versatile developmental impact on the personality of the student.

To resolve this ever-increasing contradiction, it is important, on the one hand, to convincingly reveal to the student the significance of education, the need for personal interest in it and the prospects of self-promotion in acquiring it. On the other hand, to intensify the educational process carried out at the school (UEP). The first can be achieved if the training is structured in such a way that the student WANTS and CAN recognize himself as the SUBJECT OF LEARNING, that is, such a participant in the UVP who understands and accepts his goals, owns ways to achieve them and strives to expand the range of these ways. Thus, the leading conditions for the transformation of a student into a subject of learning (within the framework of subject teaching of chemistry) is his competence in the content of the educational issues under consideration and ways of mastering them and orientation towards achieving holistic knowledge of the subject.

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Classification of chemical reactions in inorganic and organic chemistry.

/to help a young teacher/

Purpose: to systematize students' knowledge about approaches to the classification of chemical reactions. Educational tasks: · to repeat and generalize information about the classification of chemical reactions on the basis of - the number of initial and resulting substances; consider the laws of conservation of mass of matter and energy in chemical reactions as a special case of the manifestation of the universal law of nature.

Educational tasks: · to prove the leading role of theory in the knowledge of practice; Show students the relationship of opposite processes; Prove the materiality of the processes under study;

Developing tasks: development logical thinking by comparison, generalization, analysis, systematization.

Type of lesson: lesson of complex application of knowledge.

Methods and techniques: conversation, paperwork, frontal survey.

Lesson I. Organizational moment

II. Motivation learning activities students, message topics, goals, objectives of the lesson.

III. Checking students' knowledge of factual material.

Frontal conversation: 1. What types of chemical reactions do you know? (reactions of decomposition, connection, substitution and exchange). 2. Define a decomposition reaction? (Decomposition reactions are reactions in which two or more new simple or less complex substances are formed from one complex substance). 3. Define a compound reaction? (Combination reactions are reactions in which two or more substances form one more complex substance). 4. Define a substitution reaction? (Substitution reactions are reactions in which atoms a simple substance replace atoms of one of the elements in a complex substance). 5What is the definition of an exchange reaction? (Exchange reactions are reactions in which two complex substances exchange their constituent parts). 6. What is the basis of this classification? (the basis of the classification is the number of starting and formed substances)

IV. Checking students' knowledge of basic concepts, laws, theories, and the ability to explain their essence.

1. Explain the nature of chemical reactions. (The essence of chemical reactions is reduced to the breaking of bonds in the starting substances and the emergence of new chemical bonds in the reaction products. Wherein total number atoms of each element remains constant, therefore, the mass of substances does not change as a result of chemical reactions.)
2. By whom and when was this pattern established? (In 1748, the Russian scientist M.V. Lomonosov - the law of conservation of the mass of substances).

V. Checking the depth of understanding of knowledge, the degree of generalization.

Task: determine the type of chemical reaction (compound, decomposition, substitution, exchange). Give explanations for your conclusions. Set the ratios. (ICT)

	1 OPTION	OPTION 2	3 OPTION
	Mg + O 2 \u003d MgO	Fe + CuCl 2 \u003d Cu + FeCl 2	Cu + O 2 \u003d CuO
	K + H 2 O = KOH + H2	P + O 2 \u003d P 2 O 5	Fe 2 O 3 + HCl \u003d FeCl 3 + H 2 O
	Fe + H 2 SO 4 \u003d FeSO 4 + H 2	Mg + HCl = MgCl 2 + H 2	Ba + H 2 O \u003d Ba (OH) 2 + H 2
	Zn + Cu (NO 3 ) 2 \u003d Cu + Zn (NO 3 ) 2	Al 2 O 3 + HCl = AlCl 3 + H 2 O	SO 2 + H2O ↔ H 2 SO 3
	CaO + H 2 O \u003d Ca (OH) 2	P 2 O 5 + H 2 O \u003d H 3 PO 4	CuCl 2 + KOH \u003d Cu (OH) 2 + KCl
	CaO + H 3 PO 4 \u003d Ca 3 (PO 4) 2 + H 2 O	Ba(OH) 2 + HNO 3 = Ba(NO 3 ) 2 + H 2 O	Ca (OH) 2 + HNO 3 \u003d Ca (NO 3) 2 + H 2 O
	NaOH + H 2 S = Na 2 S + H 2 O	Ca + H 2 O \u003d Ca(OH) 2 +H 2	AgNO 3 + NaBr = AgBr↓ + NaNO 3
	BaCl 2 + Na 2 SO 4 \u003d BaSO 4 ↓ + NaCl	AgNO 3 + KCl \u003d AgCl + KNO 3	Cu + Hg(NO 3 ) 2 = Cu(NO 3 ) 2 + Hg
	CO 2 + H2O ↔ H 2 CO 3	Fe(OH) 3 = Fe 2 O 3 + H 2 O	Mg + HCl = MgCl 2 + H 2

VI Classification of chemical reactions in organic chemistry.

A: In inorganic chemistry, compound reactions, and in organic chemistry, such reactions are often called addition reactions (Reactions in which two or more molecules of reactants combine into one) They usually involve compounds containing a double or triple bond. Varieties of addition reactions: hydrogenation, hydration, hydrohalogenation, halogenation, polymerization. Examples of these reactions:

1. Hydrogenation - the reaction of adding a hydrogen molecule to a multiple bond:

H 2 C \u003d CH 2 + H 2 → CH 3 - CH 3

ethylene ethane

HC ≡ CH + H 2 → CH 2 = CH 2

acetylene ethylene

2. Hydrohalogenation - the reaction of the addition of a hydrogen halide to a multiple bond

H 2 C \u003d CH 2 + HCl → CH 3 ─CH 2 Cl

ethylene chloroethane

(according to the rule of V.V. Markovnikov)

H 2 C \u003d CH─CH 3 + HCl → CH 3 ─CHCl─CH 3

propylene 2 - chloropropane

HC≡CH + HCl → H 2 C=CHCl

acetylene vinyl chloride

HC≡C─CH 3 + HCl → H 2 C=CCl─CH 3

propyne 2-chloropropene

3. Hydration - the reaction of adding water to a multiple bond

H 2 C \u003d CH 2 + H 2 O → CH 3 ─CH 2 OH (primary alcohol)

ethene ethanol

(during the hydration of propene and other alkenes, secondary alcohols are formed)

HC≡CH + H 2 O → H 3 C─CHO

acetylene aldehyde - ethanal (Kucherov reaction)

4. Halogenation - the reaction of adding a halogen molecule to a multiple bond

H 2 C \u003d CH─CH 3 + Cl 2 → CH 2 Cl─CHCl─CH3

propylene 1,2 - dichloropropane

HC≡C─CH 3 + Cl 2 → HCCl=CCl─CH 3

propyne 1,2-dichloropropene

5. Polymerization - reactions during which molecules of substances with a small molecular weight are combined with each other to form molecules of substances with a high molecular weight.

n CH 2 \u003d CH 2 → (-CH 2 -CH 2 -) n

Ethylene polyethylene

B: In organic chemistry, decomposition reactions (cleavage) include: dehydration, dehydrogenation, cracking, dehydrohalogenation.

The corresponding reaction equations are:

1. Dehydration (water splitting)

C 2 H 5 OH → C 2 H 4 + H 2 O (H 2 SO 4)

2. Dehydrogenation (hydrogen elimination)

C 6 H 14 → C 6 H 6 + 4H 2

hexane benzene

3.Cracking

C 8 H 18 → C 4 H 10 + C 4 H 8

octane butane butene

4. Dehydrohalogenation (elimination of hydrogen halide)

C 2 H 5 Br → C 2 H 4 + HBr (NaOH, alcohol)

Bromoethane ethylene

Q: In organic chemistry, substitution reactions are understood more broadly, that is, not one atom, but a group of atoms can replace, or not an atom, but a group of atoms is replaced. A variety of substitution reactions include nitration and halogenation of saturated hydrocarbons, aromatic compounds, alcohols and phenol:

C 2 H 6 + Cl 2 → C 2 H 5 Cl + HCl

ethane chloroethane

C 2 H 6 + HNO 3 → C 2 H 5 NO 2 + H 2 O (Konovalov's reaction)

ethane nitroethane

C 6 H 6 + Br 2 → C 6 H 5 Br + HBr

benzene bromobenzene

C 6 H 6 + HNO 3 → C 6 H 5 NO 2 + H 2 O

benzene nitrobenzene

C 2 H 5 OH + HCl → C 2 H 5 Cl + H 2 O

Ethanol chloroethane

C 6 H 5 OH + 3Br 2 → C 6 H 2 Br 3 + 3HBr

phenol 2,4,6 - tribromophenol

D: Exchange reactions in organic chemistry are characteristic of alcohols and carboxylic acids

HCOOH + NaOH → HCOONa + H 2 O

formic acid sodium formate

(neutralization reaction)

CH 3 COOH + C 2 H 5 OH ↔ CH 3 COOC 2 H 5 + H 2 O

acetic ethanol ethyl ether acetic acid

(esterification reaction ↔ hydrolysis)

VII Consolidation of ZUN

1. When iron hydroxide (3) is heated, the reaction occurs
2. The interaction of aluminum with sulfuric acid refers to the reaction
3. The interaction of acetic acid with magnesium refers to the reaction
4. Determine the type of chemical reactions in the chain of transformations:

(use of ICT)

A) Si→SiO 2 →Na 2 SiO 3 →H 2 SiO 3 →SiO 2 →Si

B) CH 4 → C 2 H 2 → C 2 H 4 → C 2 H 5 OH → C 2 H

Classification of chemical reactions

Abstract on chemistry of a student of the 11th grade of secondary school No. 653 Alexey Nikolaev

The following can be selected as classification features:

1. The number and composition of the starting materials and reaction products.

2. State of aggregation reactants and reaction products.

3. The number of phases in which the participants in the reaction are.

4. The nature of the carried particles.

5. The possibility of a reaction proceeding in the forward and reverse direction.

6. thermal effect.

7. The phenomenon of catalysis.

Classification according to the number and composition of the starting substances and reaction products.

Connection reactions.

In the reactions of a compound from several reacting substances of a relatively simple composition, one substance of a more complex composition is obtained:

A+B+C=D

As a rule, these reactions are accompanied by heat release, i.e. lead to the formation of more stable and less energy-rich compounds.

Inorganic chemistry.

The reactions of the combination of simple substances are always redox in nature. Connection reactions occurring between complex substances can occur both without a change in valence:

CaCO 3 + CO 2 + H 2 O \u003d Ca (HCO 3) 2,

and be classified as redox:

2FeCl 2 + Cl 2 = 2FeCl 3.

Organic chemistry.

In organic chemistry, such reactions are often called addition reactions. They usually involve compounds containing a double or triple bond. Varieties of addition reactions: hydrogenation, hydration, hydrohalogenation, polymerization. Examples of these reactions:

T o

H 2 C \u003d CH 2 + H 2 → CH 3 - CH 3

ethylene ethane

T o

HC=CH + HCl → H 2 C=CHCl

acetylene vinyl chloride

T o

n CH 2 \u003d CH 2 → (-CH 2 -CH 2 -) n

Ethylene polyethylene

decomposition reactions.

Decomposition reactions lead to the formation of several compounds from one complex substance:

A = B + C + D.

The decomposition products of a complex substance can be both simple and complex substances.

Inorganic chemistry.

Of the decomposition reactions that occur without changing the valence states, it should be noted the decomposition of crystalline hydrates, bases, acids and salts of oxygen-containing acids:

	t o
CuSO 4 5H 2 O		CuSO 4 + 5H 2 O

	t o
4HNO 3		2H 2 O + 4NO 2 O + O 2 O.

2AgNO 3 \u003d 2Ag + 2NO 2 + O 2,

(NH 4) 2Cr 2 O 7 \u003d Cr 2 O 3 + N 2 + 4H 2 O.

Organic chemistry.

In organic chemistry, decomposition reactions include: dehydration, dehydrogenation, cracking, dehydrohalogenation, as well as depolymerization reactions, when the initial monomer is formed from the polymer. The corresponding reaction equations are:

T o

C 2 H 5 OH → C 2 H 4 + H 2 O

T o

C 6 H 14 → C 6 H 6 + 4H 2

hexane benzene

C 8 H 18 → C 4 H 10 + C 4 H 8

Octane Butane Butene

C 2 H5Br → C 2 H 4 + HBr

bromoethane ethylene

(-CH 2 - CH \u003d C - CH 2 -) n → n CH 2 \u003d CH - C \u003d CH 2

\CHz \CHz

natural rubber 2-methylbutadiene-1,3

substitution reactions.

In substitution reactions, usually a simple substance interacts with a complex one, forming another simple substance and another complex one:

A + BC = AB + C.

Inorganic chemistry.

These reactions in the vast majority belong to redox reactions:

2Al + Fe 2 O 3 \u003d 2Fe + Al 2 O 3

Zn + 2HCl = ZnCl 2 + H 2

2KBr + Cl 2 \u003d 2KCl + Br 2

2 KS lO 3 + l 2 \u003d 2KlO 3 + C l 2.

Examples of substitution reactions that are not accompanied by a change in the valence states of atoms are extremely few. It should be noted the reaction of silicon dioxide with salts of oxygen-containing acids, which correspond to gaseous or volatile anhydrides:

CaCO 3 + SiO 2 \u003d CaSiO 3 + CO 2

Ca 3 (RO 4) 2 + ZSiO 2 = ZCaSiO 3 + P 2 O 5

Organic chemistry.

In organic chemistry, substitution reactions are understood more broadly, that is, not one atom, but a group of atoms can replace, or not an atom, but a group of atoms is replaced. A variety of substitution reactions include nitration and halogenation of saturated hydrocarbons, aromatic compounds and alcohols:

C 6 H 6 + Br 2 → C 6 H 5 Br + HBr

benzene bromobenzene

C 2 H 5 OH + HCl → C 2 H 5 Cl + H 2 O

Ethanol chloroethane

Exchange reactions.

Exchange reactionsReactions between two compounds that exchange their constituents are called:

AB + CD = AD + CB.

Inorganic chemistry

If redox processes occur during substitution reactions, then exchange reactions always occur without changing the valence state of atoms. This is the most common group of reactions between complex substances - oxides, bases, acids and salts:

ZnO + H 2 SO 4 \u003d ZnSO 4 + H 2 O

AgNO 3 + KBr = AgBr + KNO 3

CrCl 3 + ZNaOH = Cr(OH) 3 + ZNaCl.

A special case of these exchange reactions is neutralization reactions:

Hcl + KOH \u003d KCl + H 2 O.

Usually, these reactions obey the laws of chemical equilibrium and proceed in the direction where at least one of the substances is removed from the reaction sphere in the form of a gaseous, volatile substance, precipitate, or low-dissociation (for solutions) compound:

NaHCO 3 + HCl \u003d NaCl + H 2 O + CO 2

Ca (HCO 3) 2 + Ca (OH) 2 \u003d 2CaCO 3 ↓ + 2H 2 O

Organic chemistry

HCOOH + NaOH → HCOONa + H 2 O

formic acid sodium formate

hydrolysis reactions:

Na 2 CO3 + H 2 O
NaHCO3 + NaOH

sodium carbonate sodium bicarbonate

CO 3 + H 2 O
HCO 3 + OH

esterification reactions:

CH 3 COOH + C 2 H 5 OH
CH 3 COOC 2 H 5 + H 2 O

acetic ethanol ethyl acetate

Aggregate state of reactants and reaction products.

Gas reactions

	t o
H 2 + Cl 2		2HCl.

Reactions in solutions

NaOH (pp) + Hcl (p-p) \u003d NaCl (p-p) + H 2 O (l)

Reactions between solids

	t o
CaO (tv) + SiO 2 (tv)		CaSiO 3 (TV)

The number of phases in which the participants in the reaction are.

A phase is understood as a set of homogeneous parts of a system with the same physical and chemical properties and separated from each other by an interface.

Homogeneous (single-phase) reactions.

These include reactions occurring in the gas phase, and a number of reactions occurring in solutions.

Heterogeneous (multiphase) reactions.

These include reactions in which the reactants and products of the reaction are in different phases. For example:

gas-liquid phase reactions

CO 2 (g) + NaOH (p-p) = NaHCO 3 (p-p).

gas-solid-phase reactions

CO 2 (g) + CaO (tv) \u003d CaCO 3 (tv).

liquid-solid-phase reactions

Na 2 SO 4 (pp) + BaCl 3 (pp) \u003d BaSO 4 (tv) ↓ + 2NaCl (p-p).

liquid-gas-solid-phase reactions

Ca (HCO 3) 2 (pp) + H 2 SO 4 (pp) \u003d CO 2 (r) + H 2 O (l) + CaSO 4 (tv) ↓.

The nature of the carried particles.

protolytic reactions.

Protolytic reactions include chemical processes, the essence of which is the transfer of a proton from one reactant to another.

This classification is based on the protolytic theory of acids and bases, according to which any substance that donates a proton is considered an acid, and a substance capable of accepting a proton is considered a base, for example:

Protolytic reactions include neutralization and hydrolysis reactions.

Redox reactions.

All chemical reactions are divided into those in which the oxidation states do not change (for example, the exchange reaction) and those in which the oxidation states change. They are called redox reactions. They can be decomposition reactions, compounds, substitutions and other more complex reactions. For example:

Zn + 2 H + → Zn 2 + + H 2

FeS 2 + 8HNO 3 (conc ) \u003d Fe (NO 3) 3 + 5NO + 2H 2 SO 4 + 2H 2 O

The vast majority of chemical reactions are redox, they play an extremely important role.

ligand exchange reactions.

These include reactions during which the transfer of an electron pair occurs with the formation of a covalent bond by the donor-acceptor mechanism. For example:

Cu(NO 3) 2 + 4NH 3 = (NO 3) 2

Fe + 5CO =

Al(OH) 3 + NaOH =

A characteristic feature of ligand-exchange reactions is that the formation of new compounds, called complex ones, occurs without a change in the oxidation state.

The possibility of a reaction proceeding in the forward and reverse direction.

irreversible reactions.

irreversible called such chemical processes, the products of which are not able to react with each other with the formation of starting substances. Examples of irreversible reactions are the decomposition of Bertolet salt when heated:

2KSlO 3 → 2KSl + ZO 2,

or oxidation of glucose with atmospheric oxygen:

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

reversible reactions.

reversible called such chemical processes, the products of which are able to react with each other under the same conditions in which they are obtained, with the formation of starting substances.

For reversible reactions, the equation is usually written as follows:

A+B
AB.

Two oppositely directed arrows indicate that under the same conditions, both forward and reverse reactions proceed simultaneously, for example:

CH 3 COOH + C 2 H 5 OH
CH 3 COOS 2 H 5 + H 2 O.

2SO2 +O2
2SO 3 + Q

Consequently, these reactions do not go to the end, because two reactions occur simultaneously - direct (between the starting materials) and reverse (decomposition of the reaction product).

Classification by thermal effect.

The amount of heat that is released or absorbed as a result of a reaction is called the thermal effect of this reaction. According to the thermal effect of the reaction, they are divided into:

exothermic.

Flow with heat

CH 4 + 2O 2 → CO 2 + 2H 2 O + Q

H 2 + Cl 2 → 2HC l + Q

Endothermic.

Flow with heat absorption

N 2 + O 2 → 2NO-Q

2Н 2 O → 2Н 2 + O 2 - Q

Classification taking into account the phenomenon of catalysis.

catalytic.

These include all processes involving catalysts.

Cat.

2SO2 + O2
2SO3

Non-catalytic.

These include any instantaneous reactions in solutions

BaCl 2 + H 2 SO 4 \u003d 2HCl + BaSO 4 ↓

Bibliography

Internet resources:

http://chem.km.ru - "World of Chemistry"

http:// chemi. org. ru – “Manual for applicants. Chemistry"

http://hemi. wallst. ru - "Alternative textbook in chemistry for grades 8-11"

"Guide to Chemistry. Applicants to universities "- E.T. Hovhannisyan, M. 1991

Big Encyclopedic Dictionary. Chemistry "- M. 1998.

Lecture: Classification of chemical reactions in inorganic and organic chemistry

Types of chemical reactions in inorganic chemistry

A) Classification by the number of initial substances:

Decomposition - as a result of this reaction, from one existing complex substance, two or more simple, as well as complex substances are formed.

Example: 2H 2 O 2 → 2H 2 O + O 2

Compound - this is such a reaction in which two or more simple, as well as complex substances, form one, but more complex.

Example: 4Al+3O 2 → 2Al 2 O 3

substitution - This is a certain chemical reaction that takes place between some simple, as well as complex substances. The atoms of a simple substance, in this reaction, are replaced by atoms of one of the elements found in a complex substance.

Example: 2КI + Cl2 → 2КCl + I 2

Exchange - this is such a reaction in which two substances of complex structure exchange their parts.

Example: HCl + KNO 2 → KCl + HNO 2

B) Classification by thermal effect:

exothermic reactions - These are certain chemical reactions in which heat is released.
Examples:

S + O 2 → SO 2 + Q

2C 2 H 6 + 7O 2 → 4CO 2 + 6H 2 O + Q

Endothermic reactions are certain chemical reactions in which heat is absorbed. As a rule, these are decomposition reactions.

Examples:

CaCO 3 → CaO + CO 2 - Q
2KClO 3 → 2KCl + 3O 2 - Q

The heat released or absorbed in a chemical reaction is called thermal effect.

Chemical equations in which the heat effect of a reaction is indicated are called thermochemical.

C) Classification by reversibility:

Reversible reactions are reactions that proceed under the same conditions in mutually opposite directions.

Example: 3H 2 + N 2 ⇌ 2NH 3

irreversible reactions - these are reactions that proceed only in one direction, as well as culminating in the complete consumption of all starting materials. In these reactions, isolate gas, sediment, water.
Example: 2KClO 3 → 2KCl + 3O 2

D) Classification according to the change in the degree of oxidation:

Redox reactions - in the course of these reactions, a change in the degree of oxidation occurs.

Example: Сu + 4HNO 3 → Cu(NO 3) 2 + 2NO 2 + 2H 2 O.

Not redox - reactions without changing the oxidation state.

Example: HNO 3 + KOH → KNO 3 + H 2 O.

E) Phase classification:

Homogeneous reactions – reactions occurring in one phase, when the starting materials and reaction products have the same state of aggregation.

Example: H 2 (gas) + Cl 2 (gas) → 2HCL

heterogeneous reactions - reactions occurring at the phase interface, in which the reaction products and the starting materials have a different state of aggregation.
Example: CuO+ H 2 → Cu+H 2 O

Classification by catalyst use:

A catalyst is a substance that speeds up a reaction. A catalytic reaction proceeds in the presence of a catalyst, a non-catalytic reaction without a catalyst.
Example: 2H 2 0 2 MnO2 → 2H 2 O + O 2 catalyst MnO 2

The interaction of alkali with acid proceeds without a catalyst.
Example: KOH + HCl → KCl + H 2 O

Inhibitors are substances that slow down a reaction.
Catalysts and inhibitors themselves are not consumed during the reaction.

Types of chemical reactions in organic chemistry

substitution - this is a reaction during which one atom / group of atoms is replaced in the original molecule with other atoms / groups of atoms.
Example: CH 4 + Cl 2 → CH 3 Cl + Hcl

Accession are reactions in which several molecules of a substance combine into one. Addition reactions include:

• Hydrogenation is a reaction in which hydrogen is added to a multiple bond.

Example: CH 3 -CH \u003d CH 2 (propene) + H 2 → CH 3 -CH 2 -CH 3 (propane)

Hydrohalogenation is a reaction that adds a hydrogen halide.

Example: CH 2 \u003d CH 2 (ethene) + Hcl → CH 3 -CH 2 -Cl (chloroethane)

Alkynes react with hydrogen halides (hydrogen chloride, hydrogen bromide) in the same way as alkenes. Attachment in a chemical reaction takes place in 2 stages, and is determined by the Markovnikov rule:

When protic acids and water are added to unsymmetrical alkenes and alkynes, a hydrogen atom is attached to the most hydrogenated carbon atom.

The mechanism of this chemical reaction. Formed in the 1st, fast stage, the p-complex in the 2nd slow stage gradually turns into an s-complex - a carbocation. In the 3rd stage, the stabilization of the carbocation occurs - that is, the interaction with the bromine anion:

I1, I2 - carbocations. P1, P2 - bromides.

Halogenation A reaction in which a halogen is added. Halogenation is also called all processes, as a result of which in organic compounds halogen atoms are introduced. This concept is used in broad sense". In accordance with this concept, the following chemical reactions based on halogenation are distinguished: fluorination, chlorination, bromination, iodination.

Halogen-containing organic derivatives are considered the most important compounds that are used both in organic synthesis and as target products. Halogen derivatives of hydrocarbons are considered to be the starting products in a large number of nucleophilic substitution reactions. With regard to the practical use of compounds containing halogen, they are used in the form of solvents, such as chlorine-containing compounds, refrigerants - chlorofluoro derivatives, freons, pesticides, pharmaceuticals, plasticizers, monomers for plastics.

Hydration– addition reactions of a water molecule to a multiple bond.

Polymerization - this is a special type of reaction in which molecules of a substance that have a relatively small molecular weight, join each other, subsequently forming molecules of a substance with a high molecular weight.