Chemical reactions should be distinguished from nuclear reactions. As a result chemical reactions total number atoms of each chemical element and its isotopic composition do not change. Another thing nuclear reactions- transformation processes atomic nuclei as a result of their interaction with other nuclei or elementary particles, for example, the conversion of aluminum to magnesium:

27 13 Al + 1 1 H \u003d 24 12 Mg + 4 2 He

The classification of chemical reactions is multifaceted, that is, it can be based on various signs. But under any of these signs, reactions both between inorganic and between organic substances can be attributed.

Consider the classification of chemical reactions according to various criteria.

I. According to the number and composition of the reactants

Reactions that take place without changing the composition of substances.

In not organic chemistry such reactions include the processes of obtaining allotropic modifications of one chemical element, for example:

C (graphite) ↔ C (diamond)
S (rhombic) ↔ S (monoclinic)
R (white) ↔ R (red)
Sn (white tin) ↔ Sn (grey tin)
3O 2 (oxygen) ↔ 2O 3 (ozone)

In organic chemistry, this type of reactions can include isomerization reactions that occur without changing not only the qualitative, but also the quantitative composition of the molecules of substances, for example:

1. Isomerization of alkanes.

The reaction of isomerization of alkanes is of great practical importance, since hydrocarbons of the isostructure have a lower ability to detonate.

2. Isomerization of alkenes.

3. Isomerization of alkynes (reaction of A. E. Favorsky).

CH 3 - CH 2 - C \u003d - CH ↔ CH 3 - C \u003d - C- CH 3

ethylacetylene dimethylacetylene

4. Isomerization of haloalkanes (A. E. Favorsky, 1907).

5. Isomerization of ammonium cyanite upon heating.

For the first time, urea was synthesized by F. Wehler in 1828 by isomerization of ammonium cyanate when heated.

Reactions that go with a change in the composition of a substance

There are four types of such reactions: compounds, decompositions, substitutions and exchanges.

1. Connection reactions are such reactions in which one complex substance is formed from two or more substances

In inorganic chemistry, the whole variety of compound reactions can be considered, for example, using the example of reactions for obtaining sulfuric acid from sulfur:

1. Obtaining sulfur oxide (IV):

S + O 2 \u003d SO - from two simple substances one complex is formed.

2. Obtaining sulfur oxide (VI):

SO 2 + 0 2 → 2SO 3 - one complex substance is formed from a simple and complex substance.

3. Obtaining sulfuric acid:

SO 3 + H 2 O \u003d H 2 SO 4 - one complex is formed from two complex substances.

An example of a compound reaction in which one complex substance is formed from more than two starting materials is the final stage in the production of nitric acid:

4NO 2 + O 2 + 2H 2 O \u003d 4HNO 3

In organic chemistry, compound reactions are commonly referred to as "addition reactions". The whole variety of such reactions can be considered on the example of a block of reactions characterizing the properties of unsaturated substances, for example, ethylene:

1. Hydrogenation reaction - hydrogen addition:

CH 2 \u003d CH 2 + H 2 → H 3 -CH 3

ethene → ethane

2. Hydration reaction - addition of water.

3. Polymerization reaction.

2. Decomposition reactions are such reactions in which several new substances are formed from one complex substance.

In inorganic chemistry, the whole variety of such reactions can be considered in the block of reactions for obtaining oxygen by laboratory methods:

1. Decomposition of mercury (II) oxide - two simple ones are formed from one complex substance.

2. Decomposition of potassium nitrate - from one complex substance, one simple and one complex are formed.

3. Decomposition of potassium permanganate - from one complex substance, two complex and one simple are formed, that is, three new substances.

In organic chemistry, decomposition reactions can be considered on the block of reactions for the production of ethylene in the laboratory and in industry:

1. The reaction of dehydration (water splitting) of ethanol:

C 2 H 5 OH → CH 2 \u003d CH 2 + H 2 O

2. Dehydrogenation reaction (hydrogen splitting) of ethane:

CH 3 -CH 3 → CH 2 \u003d CH 2 + H 2

or CH 3 -CH 3 → 2C + ZH 2

3. Cracking reaction (splitting) of propane:

CH 3 -CH 2 -CH 3 → CH 2 \u003d CH 2 + CH 4

3. Substitution reactions are such reactions as a result of which the atoms of a simple substance replace the atoms of an element in a complex substance.

In inorganic chemistry, an example of such processes is a block of reactions that characterize the properties of, for example, metals:

1. Interaction of alkali or alkaline earth metals with water:

2Na + 2H 2 O \u003d 2NaOH + H 2

2. Interaction of metals with acids in solution:

Zn + 2HCl = ZnCl 2 + H 2

3. Interaction of metals with salts in solution:

Fe + CuSO 4 = FeSO 4 + Cu

4. Metalthermy:

2Al + Cr 2 O 3 → Al 2 O 3 + 2Cr

The subject of study of organic chemistry is not simple substances, but only compounds. Therefore, as an example of a substitution reaction, we present the most characteristic property saturated compounds, in particular methane, is the ability of its hydrogen atoms to be replaced by halogen atoms. Another example is bromination aromatic compound(benzene, toluene, aniline).

C 6 H 6 + Br 2 → C 6 H 5 Br + HBr

benzene → bromobenzene

Let us pay attention to the peculiarity of the substitution reaction at organic matter: as a result of such reactions, not a simple and complex substance is formed, as in inorganic chemistry, but two complex substances.

In organic chemistry, substitution reactions also include some reactions between two complex substances, for example, the nitration of benzene. It is formally an exchange reaction. The fact that this is a substitution reaction becomes clear only when considering its mechanism.

4. Exchange reactions are such reactions in which two complex substances exchange their constituent parts

These reactions characterize the properties of electrolytes and proceed in solutions according to the Berthollet rule, that is, only if a precipitate, gas, or a low-dissociating substance (for example, H 2 O) is formed as a result.

In inorganic chemistry, this can be a block of reactions characterizing, for example, the properties of alkalis:

1. Neutralization reaction that goes with the formation of salt and water.

2. The reaction between alkali and salt, which goes with the formation of gas.

3. The reaction between alkali and salt, which goes with the formation of a precipitate:

СuSO 4 + 2KOH \u003d Cu (OH) 2 + K 2 SO 4

or in ionic form:

Cu 2+ + 2OH - \u003d Cu (OH) 2

In organic chemistry, one can consider a block of reactions characterizing, for example, the properties of acetic acid:

1. The reaction proceeding with the formation of a weak electrolyte - H 2 O:

CH 3 COOH + NaOH → Na (CH3COO) + H 2 O

2. The reaction that goes with the formation of gas:

2CH 3 COOH + CaCO 3 → 2CH 3 COO + Ca 2+ + CO 2 + H 2 O

3. The reaction proceeding with the formation of a precipitate:

2CH 3 COOH + K 2 SO 3 → 2K (CH 3 COO) + H 2 SO 3

2CH 3 COOH + SiO → 2CH 3 COO + H 2 SiO 3

II. By changing oxidation states chemical elements, forming substances

On this basis, the following reactions are distinguished:

1. Reactions that occur with a change in the oxidation states of elements, or redox reactions.

These include many reactions, including all substitution reactions, as well as those reactions of combination and decomposition in which at least one simple substance participates, for example:

1. Mg 0 + H + 2 SO 4 \u003d Mg + 2 SO 4 + H 2

2. 2Mg 0 + O 0 2 = Mg +2 O -2

Complex redox reactions are compiled using the electron balance method.

2KMn +7 O 4 + 16HCl - \u003d 2KCl - + 2Mn +2 Cl - 2 + 5Cl 0 2 + 8H 2 O

In organic chemistry a prime example redox reactions can serve as properties of aldehydes.

1. They are reduced to the corresponding alcohols:

Aldecides are oxidized to the corresponding acids:

2. Reactions that take place without changing the oxidation states of chemical elements.

These include, for example, all ion exchange reactions, as well as many compound reactions, many decomposition reactions, esterification reactions:

HCOOH + CHgOH = HSOCH 3 + H 2 O

III. By thermal effect

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

1. Exothermic reactions proceed with the release of energy.

These include almost all compound reactions. A rare exception is the endothermic reactions of the synthesis of nitric oxide (II) from nitrogen and oxygen and the reaction of gaseous hydrogen with solid iodine.

Exothermic reactions that proceed with the release of light are referred to as combustion reactions. The hydrogenation of ethylene is an example of an exothermic reaction. It runs at room temperature.

2. Endothermic reactions proceed with the absorption of energy.

Obviously, almost all decomposition reactions will apply to them, for example:

1. Calcination of limestone

2. Butane cracking

The amount of energy released or absorbed as a result of the reaction is called the thermal effect of the reaction, and the equation of a chemical reaction indicating this effect is called the thermochemical equation:

H 2 (g) + C 12 (g) \u003d 2HC 1 (g) + 92.3 kJ

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

IV. According to the state of aggregation of reacting substances (phase composition)

According to the state of aggregation of the reacting substances, there are:

1. Heterogeneous reactions - reactions in which the reactants and reaction products are in different states of aggregation (in different phases).

2. Homogeneous reactions - reactions in which the reactants and reaction products are in the same state of aggregation(in one phase).

V. According to the participation of the catalyst

According to the participation of the catalyst, there are:

1. Non-catalytic reactions that take place without the participation of a catalyst.

2. Catalytic reactions taking place with the participation of a catalyst. Since all biochemical reactions occurring in the cells of living organisms proceed with the participation of special biological catalysts of protein nature - enzymes, they are all catalytic or, more precisely, enzymatic. It should be noted that more than 70% of chemical industries use catalysts.

VI. Towards

By direction there are:

1. irreversible reactions flow under these conditions in only one direction. These include all exchange reactions accompanied by the formation of a precipitate, gas or a low-dissociating substance (water) and all combustion reactions.

2. Reversible reactions under these conditions proceed simultaneously in two opposite directions. Most of these reactions are.

In organic chemistry, the sign of reversibility is reflected in the names - antonyms of processes:

Hydrogenation - dehydrogenation,

Hydration - dehydration,

Polymerization - depolymerization.

All esterification reactions are reversible (the opposite process, as you know, is called hydrolysis) and protein hydrolysis, esters, carbohydrates, polynucleotides. The reversibility of these processes underlies the most important property living organism - metabolism.

VII. According to the mechanism of flow, there are:

1. Radical reactions take place between the radicals and molecules formed during the reaction.

As you already know, in all reactions, old chemical bonds are broken and new chemical bonds are formed. The method of breaking the bond in the molecules of the starting substance determines the mechanism (path) of the reaction. If the substance is formed by a covalent bond, then there can be two ways to break this bond: hemolytic and heterolytic. For example, for the molecules of Cl 2 , CH 4 , etc., a hemolytic rupture of bonds is realized, it will lead to the formation of particles with unpaired electrons, that is, free radicals.

Radicals are most often formed when bonds are broken in which the shared electron pairs are distributed approximately equally between atoms (non-polar covalent bond), but many polar bonds can also be broken in a similar way, in particular when the reaction takes place in the gas phase and under the influence of light , as, for example, in the case of the processes discussed above - the interaction of C 12 and CH 4 - . Radicals are highly reactive, as they tend to complete their electron layer by taking an electron from another atom or molecule. For example, when a chlorine radical collides with a hydrogen molecule, it causes a break in the common electron pair that binds hydrogen atoms and forms covalent bond with one of the hydrogen atoms. The second hydrogen atom, becoming a radical, forms a common electron pair with the unpaired electron of the chlorine atom from the collapsing Cl 2 molecule, resulting in a chlorine radical that attacks a new hydrogen molecule, etc.

Reactions, which are a chain of successive transformations, are called chain reactions. For the development of the theory of chain reactions, two outstanding chemists - our compatriot N. N. Semenov and the Englishman S. A. Hinshelwood were awarded the Nobel Prize.
The substitution reaction between chlorine and methane proceeds similarly:

Most of the combustion reactions of organic and inorganic substances, the synthesis of water, ammonia, the polymerization of ethylene, vinyl chloride, etc. proceed according to the radical mechanism.

2. Ionic reactions take place between ions already present or formed during the reaction.

Typical ionic reactions is the interaction between electrolytes in solution. Ions are formed not only during the dissociation of electrolytes in solutions, but also under the action of electrical discharges, heating or radiation. γ-rays, for example, convert water and methane molecules into molecular ions.

According to another ionic mechanism, there are reactions of addition of hydrogen halides, hydrogen, halogens to alkenes, oxidation and dehydration of alcohols, replacement of alcohol hydroxyl by halogen; reactions characterizing the properties of aldehydes and acids. Ions in this case are formed by heterolytic breaking of covalent polar bonds.

VIII. According to the type of energy

initiating the reaction, there are:

1. Photochemical reactions. They are initiated by light energy. In addition to the above photochemical processes of HCl synthesis or the reaction of methane with chlorine, they include the production of ozone in the troposphere as a secondary atmospheric pollutant. In this case, nitric oxide (IV) acts as the primary one, which forms oxygen radicals under the action of light. These radicals interact with oxygen molecules, resulting in ozone.

The formation of ozone goes on as long as there is enough light, since NO can interact with oxygen molecules to form the same NO 2 . The accumulation of ozone and other secondary air pollutants can lead to photochemical smog.

This type of reaction also includes the most important process that occurs in plant cells - photosynthesis, the name of which speaks for itself.

2. Radiation reactions. They are initiated by high-energy radiation - x-rays, nuclear radiation (γ-rays, a-particles - He 2+, etc.). With the help of radiation reactions, very fast radiopolymerization, radiolysis (radiation decomposition), etc. are carried out.

For example, instead of a two-stage production of phenol from benzene, it can be obtained by the interaction of benzene with water under the action of radiation. In this case, radicals [OH] and [H] are formed from water molecules, with which benzene reacts to form phenol:

C 6 H 6 + 2 [OH] → C 6 H 5 OH + H 2 O

Rubber vulcanization can be carried out without sulfur using radiovulcanization, and the resulting rubber will be no worse than traditional rubber.

3. Electrochemical reactions. They are initiated electricity. In addition to the well-known electrolysis reactions, we also indicate the reactions of electrosynthesis, for example, the reactions industrial production inorganic oxidizers

4. Thermochemical reactions. They are initiated by thermal energy. These include all endothermic reactions and many exothermic reactions that require an initial supply of heat, that is, the initiation of the process.

The above classification of chemical reactions is reflected in the diagram.

The classification of chemical reactions, like all other classifications, is conditional. Scientists agreed to divide the reactions into certain types according to the signs they identified. But most chemical transformations can be attributed to different types. For example, let's characterize the ammonia synthesis process.

This is a compound reaction, redox, exothermic, reversible, catalytic, heterogeneous (more precisely, heterogeneous catalytic), proceeding with a decrease in pressure in the system. To successfully manage the process, all of the above information must be taken into account. A specific chemical reaction is always multi-qualitative, it is characterized by different features.

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: · repeat and summarize information about the classification of chemical reactions on the basis - the number of starting and obtained substances; consider the laws of conservation of mass of matter and energy in chemical reactions as special case 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 of logical thinking through 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 of a simple substance replace the atoms of one of the elements in a complex substance). fiveWhat is the definition of an exchange reaction? (Exchange reactions are reactions in which two complex substances exchange their constituents). 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 initial substances and the emergence of new chemical bonds in the reaction products. In this case, the total number of 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. Substitution reactions include nitration and halogenation. 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 acetate

(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 in inorganic and organic chemistry

Chemical reactions, or chemical phenomena, are processes as a result of which others are formed from some substances, differing from them in composition and (or) structure.

In chemical reactions, a change in substances necessarily occurs, in which old bonds are broken and new bonds are formed between atoms.

Chemical reactions should be distinguished from nuclear reactions. As a result of a chemical reaction, the total number of atoms of each chemical element and its isotopic composition do not change. Nuclear reactions are another matter - the processes of transformation of atomic nuclei as a result of their interaction with other nuclei or elementary particles, for example, the transformation of aluminum into magnesium:

$↙(13)↖(27)(Al)+ ()↙(1)↖(1)(H)=()↙(12)↖(24)(Mg)+()↙(2)↖(4 )(He)$

The classification of chemical reactions is multifaceted, i.e. It can be based on various features. But under any of these signs, reactions both between inorganic and between organic substances can be attributed.

Consider the classification of chemical reactions according to various criteria.

Classification of chemical reactions according to the number and composition of reactants. Reactions that take place without changing the composition of the substance

In inorganic chemistry, such reactions include the processes of obtaining allotropic modifications of one chemical element, for example:

$С_((graphite))⇄С_((diamond))$

$S_((rhombic))⇄S_((monoclinic))$

$P_((white))⇄P_((red))$

$Sn_((white tin))⇄Sn_((grey tin))$

$3O_(2(oxygen))⇄2O_(3(ozone))$.

In organic chemistry, this type of reactions can include isomerization reactions that occur without changing not only the qualitative, but also the quantitative composition of the molecules of substances, for example:

1. Isomerization of alkanes.

The reaction of isomerization of alkanes is of great practical importance, because. isostructure hydrocarbons are less prone to detonation.

2. Alkene isomerization.

3. Alkyne isomerization(reaction of A. E. Favorsky).

4. Isomerization of haloalkanes(A. E. Favorsky).

5. Isomerization of ammonium cyanate on heating.

For the first time, urea was synthesized by F. Wehler in 1882 by isomerization of ammonium cyanate when heated.

Reactions that go with a change in the composition of a substance

There are four types of such reactions: compounds, decompositions, substitutions and exchanges.

1. Connection reactions- These are reactions in which two or more substances form one complex substance.

In inorganic chemistry, the whole variety of compound reactions can be considered using the example of reactions for obtaining sulfuric acid from sulfur:

1) obtaining sulfur oxide (IV):

$S+O_2=SO_2$ — one complex substance is formed from two simple substances;

2) production of sulfur oxide (VI):

$2SO_2+O_2(⇄)↖(t,p,cat.)2SO_3$ - one complex substance is formed from simple and complex substances;

3) obtaining sulfuric acid:

$SO_3+H_2O=H_2SO_4$ — one compound is formed from two complex substances.

An example of a compound reaction in which one complex substance is formed from more than two starting materials is the final stage in the production of nitric acid:

$4NO_2+O_2+2H_2O=4HNO_3$.

In organic chemistry, compound reactions are commonly referred to as addition reactions. The whole variety of such reactions can be considered on the example of a block of reactions characterizing the properties of unsaturated substances, for example, ethylene:

1) hydrogenation reaction - addition of hydrogen:

$CH_2(=)↙(ethene)CH_2+H_2(→)↖(Ni,t°)CH_3(-)↙(ethane)CH_3;$

2) hydration reaction - addition of water:

$CH_2(=)↙(ethene)CH_2+H_2O(→)↖(H_3PO_4,t°)(C_2H_5OH)↙(ethanol);$

3) polymerization reaction:

$(nCH_2=CH_2)↙(ethylene)(→)↖(p,cat.,t°)((-CH_2-CH_2-)_n)↙(polyethylene)$

2. Decomposition reactions These are reactions in which several new substances are formed from one complex substance.

In inorganic chemistry, the whole variety of such reactions can be considered using the example of a block of reactions for obtaining oxygen by laboratory methods:

1) decomposition of mercury oxide (II):

$2HgO(→)↖(t°)2Hg+O_2$ — two simple substances are formed from one complex substance;

2) decomposition of potassium nitrate:

$2KNO_3(→)↖(t°)2KNO_2+O_2$ — from one complex substance one simple and one complex substance are formed;

3) decomposition of potassium permanganate:

$2KMnO_4(→)↖(t°)K_2MnO_4+MnO_2+O_2$ — from one complex substance two complex and one simple are formed, i.e. three new substances.

In organic chemistry, decomposition reactions can be considered using the example of a block of reactions for the production of ethylene in the laboratory and industry:

1) the reaction of dehydration (water splitting) of ethanol:

$C_2H_5OH(→)↖(H_2SO_4,t°)CH_2=CH_2+H_2O;$

2) the reaction of dehydrogenation (hydrogen elimination) of ethane:

$CH_3—CH_3(→)↖(Cr_2O_3,500°C)CH_2=CH_2+H_2;$

3) propane cracking (splitting) reaction:

$CH_3-CH_2CH_3(→)↖(t°)CH_2=CH_2+CH_4.$

3. Substitution reactions- these are reactions in which the atoms of a simple substance replace the atoms of an element in a complex substance.

In inorganic chemistry, an example of such processes is a block of reactions that characterize the properties of, for example, metals:

1) interaction of alkali and alkaline earth metals with water:

$2Na+2H_2O=2NaOH+H_2$

2) interaction of metals with acids in solution:

$Zn+2HCl=ZnCl_2+H_2$;

3) interaction of metals with salts in solution:

$Fe+CuSO_4=FeSO_4+Cu;$

4) metallothermy:

$2Al+Cr_2O_3(→)↖(t°)Al_2O_3+2Cr$.

The subject of study of organic chemistry is not simple substances, but only compounds. Therefore, as an example of a substitution reaction, we give the most characteristic property of saturated compounds, in particular methane, the ability of its hydrogen atoms to be replaced by halogen atoms:

$CH_4+Cl_2(→)↖(hν)(CH_3Cl)↙(chloromethane)+HCl$,

$CH_3Cl+Cl_2→(CH_2Cl_2)↙(dichloromethane)+HCl$,

$CH_2Cl_2+Cl_2→(CHCl_3)↙(trichloromethane)+HCl$,

$CHCl_3+Cl_2→(CCl_4)↙(tetrachloromethane)+HCl$.

Another example is the bromination of an aromatic compound (benzene, toluene, aniline):

Let us pay attention to the peculiarity of substitution reactions in organic substances: as a result of such reactions, not a simple and complex substance is formed, as in inorganic chemistry, but two complex substances.

In organic chemistry, substitution reactions also include some reactions between two complex substances, for example, the nitration of benzene:

$C_6H_6+(HNO_3)↙(benzene)(→)↖(H_2SO_4(conc.),t°)(C_6H_5NO_2)↙(nitrobenzene)+H_2O$

It is formally an exchange reaction. The fact that this is a substitution reaction becomes clear only when considering its mechanism.

4. Exchange reactions- these are reactions in which two complex substances exchange their constituent parts.

These reactions characterize the properties of electrolytes and proceed in solutions according to the Berthollet rule, i.e. only if the result is a precipitate, a gas, or a low-dissociation substance (for example, $H_2O$).

In inorganic chemistry, this can be a block of reactions characterizing, for example, the properties of alkalis:

1) a neutralization reaction that goes with the formation of salt and water:

$NaOH+HNO_3=NaNO_3+H_2O$

or in ionic form:

$OH^(-)+H^(+)=H_2O$;

2) the reaction between alkali and salt, which goes with the formation of gas:

$2NH_4Cl+Ca(OH)_2=CaCl_2+2NH_3+2H_2O$

or in ionic form:

$NH_4^(+)+OH^(-)=NH_3+H_2O$;

3) the reaction between alkali and salt, which proceeds with the formation of a precipitate:

$CuSO_4+2KOH=Cu(OH)_2↓+K_2SO_4$

or in ionic form:

$Cu^(2+)+2OH^(-)=Cu(OH)_2↓$

In organic chemistry, one can consider a block of reactions characterizing, for example, the properties of acetic acid:

1) a reaction proceeding with the formation of a weak electrolyte - $H_2O$:

$CH_3COOH+NaOH⇄NaCH_3COO+H_2O$

$CH_3COOH+OH^(-)⇄CH_3COO^(-)+H_2O$;

2) the reaction proceeding with the formation of gas:

$2CH_3COOH+CaCO_3=2CH_3COO^(-)+Ca^(2+)+CO_2+H_2O$;

3) reaction proceeding with the formation of a precipitate:

$2CH_3COOH+K_2SiO_3=2KCH_3COO+H_2SiO_3↓$

$2CH_3COOH+SiO_3^(−)=2CH_3COO^(−)+H_2SiO_3↓$.

Classification of chemical reactions according to the change in the oxidation states of chemical elements that form substances

Reactions that occur with a change in the oxidation states of elements, or redox reactions.

These include many reactions, including all substitution reactions, as well as those reactions of combination and decomposition in which at least one simple substance participates, for example:

1.$(Mg)↖(0)+(2H)↖(+1)+SO_4^(-2)=(Mg)↖(+2)SO_4+(H_2)↖(0)$

$((Mg)↖(0)-2(e)↖(-))↙(reducing agent)(→)↖(oxidation)(Mg)↖(+2)$

$((2H)↖(+1)+2(e)↖(-))↙(oxidizer)(→)↖(reduction)(H_2)↖(0)$

2.$(2Mg)↖(0)+(O_2)↖(0)=(2Mg)↖(+2)(O)↖(-2)$

$((Mg)↖(0)-2(e)↖(-))↙(reductant)(→)↖(oxidation)(Mg)↖(+2)|4|2$

$((O_2)↖(0)+4(e)↖(-))↙(oxidizer)(→)↖(reduction)(2O)↖(-2)|2|1$

As you remember, complex redox reactions are compiled using the electron balance method:

$(2Fe)↖(0)+6H_2(S)↖(+6)O_(4(k))=(Fe_2)↖(+3)(SO_4)_3+3(S)↖(+4)O_2+ 6H_2O$

$((Fe)↖(0)-3(e)↖(-))↙(reducing agent)(→)↖(oxidation)(Fe)↖(+3)|2$

$((S)↖(+6)+2(e)↖(-))↙(oxidizer)(→)↖(reduction)(S)↖(+4)|3$

In organic chemistry, the properties of aldehydes can serve as a striking example of redox reactions:

1. Aldehydes are reduced to the corresponding alcohols:

$(CH_3-(C)↖(+1) ()↖(O↖(-2))↙(H↖(+1))+(H_2)↖(0))↙(\text"acetaldehyde") (→)↖(Ni,t°)(CH_3-(C)↖(-1)(H_2)↖(+1)(O)↖(-2)(H)↖(+1))↙(\text "ethyl alcohol")$

$((C)↖(+1)+2(e)↖(-))↙(oxidizer)(→)↖(reduction)(C)↖(-1)|1$

$((H_2)↖(0)-2(e)↖(-))↙(reductant)(→)↖(oxidation)2(H)↖(+1)|1$

2. Aldehydes are oxidized to the corresponding acids:

$(CH_3-(C)↖(+1) ()↖(O↖(-2))↙(H↖(+1))+(Ag_2)↖(+1)(O)↖(-2)) ↙(\text"acetaldehyde")(→)↖(t°)(CH_3-(Ag)↖(0)(C)↖(+3)(O)↖(-2)(OH)↖(-2 +1)+2(Ag)↖(0)↓)↙(\text"ethyl alcohol")$

$((C)↖(+1)-2(e)↖(-))↙(reducing agent)(→)↖(oxidation)(C)↖(+3)|1$

$(2(Ag)↖(+1)+2(e)↖(-))↙(oxidizer)(→)↖(reduction)2(Ag)↖(0)|1$

Reactions that take place without changing the oxidation states of chemical elements.

These include, for example, all ion exchange reactions, as well as:

• many compound reactions:

$Li_2O+H_2O=2LiOH;$

• many decomposition reactions:

$2Fe(OH)_3(→)↖(t°)Fe_2O_3+3H_2O;$

• esterification reactions:

$HCOOH+CH_3OH⇄HCOOCH_3+H_2O$.

Classification of chemical reactions by thermal effect

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

exothermic reactions.

These reactions proceed with the release of energy.

These include almost all compound reactions. A rare exception is the endothermic reactions of the synthesis of nitric oxide (II) from nitrogen and oxygen and the reaction of gaseous hydrogen with solid iodine:

$N_2+O_2=2NO - Q$,

$H_(2(t))+I(2(t))=2HI - Q$.

Exothermic reactions that proceed with the release of light are referred to as combustion reactions, for example:

$4P+5O_2=2P_2O_5+Q,$

$CH_4+2O_2=CO_2+2H_2O+Q$.

The hydrogenation of ethylene is an example of an exothermic reaction:

$CH_2=CH_2+H_2(→)↖(Pt)CH_3-CH_3+Q$

It runs at room temperature.

Endothermic reactions

These reactions proceed with the absorption of energy.

Obviously, almost all decomposition reactions belong to them, for example:

a) burning limestone:

$CaCO_3(→)↖(t°)CaO+CO_2-Q;$

b) butane cracking:

The amount of energy released or absorbed in a reaction is called the thermal effect of the reaction, and the equation of a chemical reaction indicating this effect is called thermochemical equation, for example:

$H_(2(g))+Cl_(2(g))=2HCl_((g))+92.3 kJ,$

$N_(2(g))+O_(2(g))=2NO_((g)) - 90.4 kJ$.

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

heterogeneous reactions.

These are reactions in which the reactants and reaction products are in different states of aggregation (in different phases):

$2Al_((m))+3CuCl_(2(r-r))=3Cu_((t))+2AlCl_(3(r-r))$,

$CaC_(2(t))+2H_2O_((l))=C_2H_2+Ca(OH)_(2(solid))$.

homogeneous reactions.

These are reactions in which the reactants and reaction products are in the same state of aggregation (in the same phase):

Classification of chemical reactions according to the participation of a catalyst

non-catalytic reactions.

Non-catalytic reactions go without the participation of a catalyst:

$2HgO(→)↖(t°)2Hg+O_2$,

$C_2H_4+3O_2(→)↖(t°)2CO_2+2H_2O$.

catalytic reactions.

catalytic reactions going on with a catalyst:

$2KClO_3(→)↖(MnO_2,t°)2KCl+3O_2,$

$(C_2H_5OH)↙(ethanol)(→)↖(H_2SO-4,t°)(CH_2=CH_2)↙(ethene)+H_2O$

Since all biological reactions occurring in the cells of living organisms proceed with the participation of special biological catalysts of a protein nature - enzymes, they all belong to catalytic or, more precisely, enzymatic.

It should be noted that more than $70%$ of chemical industries use catalysts.

Classification of chemical reactions by direction

irreversible reactions.

irreversible reactions flow under these conditions in only one direction.

These include all exchange reactions accompanied by the formation of a precipitate, gas or a low-dissociating substance (water), and all combustion reactions.

reversible reactions.

Reversible reactions under these conditions proceed simultaneously in two opposite directions.

Most of these reactions are.

In organic chemistry, the sign of reversibility is reflected in the names-antonyms of processes:

• hydrogenation - dehydrogenation;
• hydration - dehydration;
• polymerization - depolymerization.

All esterification reactions are reversible (the opposite process, as you know, is called hydrolysis) and hydrolysis of proteins, esters, carbohydrates, polynucleotides. Reversibility underlies the most important process in a living organism - metabolism.

Lesson goals. To generalize the idea of ​​a chemical reaction as a process of transformation of one or more initial substances-reagents into substances that differ from them in chemical composition or structure - reaction products. Consider some of the many classifications of chemical reactions according to various criteria. Show the applicability of such classifications for inorganic and organic reactions. Reveal the relative nature of various types of chemical reactions and the relationship of various classifications of chemical processes.

The concept of chemical reactions, their classification according to various criteria in comparison for inorganic and organic substances

A chemical reaction is such a change in substances in which old chemical bonds are broken and new chemical bonds are formed between the particles (“volumes, ions) from which substances are built (slide 2).

Chemical reactions are classified:
1. By the number and composition of reagents and products (slide 3)
a) expansions (slide 4)
Decomposition reactions in organic chemistry, in contrast to decomposition reactions in inorganic chemistry, have their own specifics. They can be considered as the reverse processes of addition, since the result most often is the formation of multiple bonds or cycles.
b) connections (slide 5)
In order to enter into an addition reaction, organic molecule must have a multiple bond (or cycle), this molecule will be the main one (substrate). A simpler molecule (often inorganic matter, reagent) is attached at the site of the break of a multiple bond or ring opening.
c) substitutions (slide 6)
Their distinguishing feature is the interaction of a simple substance with a complex one. Such reactions exist in organic chemistry.
However, the concept of "substitution" in organics is broader than in inorganic chemistry. If in the molecule of the original substance any atom or functional group is replaced by another atom or group, these are also substitution reactions, although from the point of view of inorganic chemistry, the process looks like an exchange reaction.
d) exchange (including neutralization) (slide 7)
It is recommended to carry out in the form laboratory work according to the reaction equations proposed in the presentation

2. By thermal effect (slide 8)
a) endothermic
b) exothermic (including combustion reactions)
The presentation suggested reactions from inorganic and organic chemistry. Combination reactions will be exothermic reactions, and decomposition reactions will be endothermic (the relativity of this conclusion will be emphasized by a rare exception - the reaction of nitrogen with oxygen is endothermic:
N 2 + 0 2 -> 2 NO- Q

3. On the use of a catalyst (slide 9)
b) non-catalytic

4. Direction (slide 10)
a) catalytic (including enzymatic)
b) non-catalytic

5. By phase (slide 11)
a) homogeneous
b) heterogeneous

6. By changing the oxidation state of elements that form reactants and products (slide 12)
a) redox
b) without changing the oxidation state
Redox in inorganic chemistry includes all substitution reactions and those decomposition and compound reactions in which at least one simple substance is involved. In a more generalized version (already taking into account organic chemistry): all reactions involving simple substances. Conversely, reactions proceeding without changing the oxidation states of the elements that form the reactants and reaction products include all exchange reactions.

Consolidation of the studied topic (slide 13-21).

Summary of the lesson.

Lesson 2 Chemical properties, methods for obtaining saturated monobasic carboxylic acids "(Slide 1).

Lesson goals. Give the concept of carboxylic acids and their classification in comparison with mineral acids. Consider the basics of international and trivial nomenclature and isomerism of this type organic compounds. Disassemble the structure of the carboxyl group and predict the chemical behavior of carboxylic acids. Consider general properties carboxylic acids in comparison with the properties of mineral acids. Give an idea of ​​the special properties of carboxylic acids (radical reactions and the formation of functional derivatives). To acquaint students with the most characteristic representatives of carboxylic acids and show their significance in nature and in human life.

The concept of carboxylic acids, their classification according to various criteria

carboxylic acids- a class of organic compounds whose molecules contain a carboxyl group - COOH. The composition of limiting monobasic carboxylic acids corresponds to the general formula (Slide 2)

Carboxylic acids are classified:
According to the number of carboxyl groups carboxylic acids divided into (Slide 3):

• monocarboxylic or monobasic (acetic acid)
• dicarboxylic or dibasic (oxalic acid)

Depending on the structure of the hydrocarbon radical to which the carboxyl group is attached, carboxylic acids are divided into:

• aliphatic (acetic or acrylic)
• alicyclic (cyclohexanecarboxylic)
• aromatic (benzoic, phthalic)

Examples of acids (Slide 4)

Isomerism and structure of carboxylic acids
1. Isomerism of the carbon chain (Slide 5)
2. Isomerism of the position of a multiple bond, for example:
CH 2 \u003d CH - CH 2 - COOH Butene-3-oic acid (vinylacetic acid)
CH 3 - CH \u003d CH - COOH Butene-2-oic acid (crotonic acid)

3. Cis-, trans-isomerism, for example:

Structure(Slide 6)
The carboxyl group COOH consists of the carbonyl group C=O and the hydroxyl group OH.
In the CO group, the carbon atom carries a partial positive charge and attracts the electron pair of the oxygen atom in the OH group. In this case, the electron density on the oxygen atom decreases, and O-N connection weakened:

In turn, the OH group "extinguishes" the positive charge on the CO group.

Physical and chemical properties of carboxylic acids
Lower carboxylic acids are liquids with a pungent odor, highly soluble in water. With increasing relative molecular weight The solubility of acids in water decreases and the boiling point rises. Higher acids, starting with pelargonic

C 8 H 17 COOH - solids, odorless, insoluble in water.
The most important chemical properties characteristic of most carboxylic acids (Slide 7.8):
1) Interaction with active metals:
2 CH 3 COOH + Mg (CH 3 COO) 2 Mg + H 2

2) Interaction with metal oxides:
2CH 3 COOH + CaO (CH 3 COO) 2 Ca + H 2 O

3) Interaction with bases:
CH 3 COOH + NaOHCH 3 COONa + H 2 O

4) Interaction with salts:
CH 3 COOH + NaHCO 3 CH 3 COONa + CO 2 + H 2 O

5) Interaction with alcohols (esterification reaction):
CH 3 COOH + CH 3 CH 2 OHCH 3 COOSH 2 CH 3 + H 2 O

6) Interaction with ammonia:
CH 3 COOH + NH 3 CH 3 COONH 4
When heated, ammonium salts of carboxylic acids form their amides:
CH 3 COONH 4 CH 3 CONH 2 + H 2 O
7) Under the action of SOC l2, carboxylic acids are converted into the corresponding acid chlorides.
CH 3 COOH + SOC l2 CH 3 COCl + HCl + SO 2

4. Interclass isomerism : for example: C 4 H 8 O 2
CH 3 - CH 2 - CO - O - CH 3 propanoic acid methyl ester
CH 3 - CO - O - CH 2 - CH 3 ethanoic acid ethyl ester
С3Н 7 - COOH butanoic acid

(Slide 9,10)
1. Oxidation of aldehydes and primary alcohols - general method for obtaining carboxylic acids:

2. Another general method is the hydrolysis of halogenated hydrocarbons containing three halogen atoms on one carbon atom:

3 NaCl
3. Interaction of the Grignard reagent with CO2:

4. Hydrolysis of esters:

5. Hydrolysis of acid anhydrides:

Methods for obtaining carboxylic acids
For individual acids there are specific ways to obtain (Slide 11):
For getting benzoic acid you can use the oxidation of monosubstituted benzene homologues with an acidic solution of potassium permanganate:

Acetic acid obtained on an industrial scale by catalytic oxidation of butane with atmospheric oxygen:

Formic acid obtained by heating carbon monoxide (II) with powdered sodium hydroxide under pressure and processing the resulting sodium formate with a strong acid:

Application of carboxylic acids(Slide 12)

Consolidation of the studied topic (slide 13-14).

In inorganic chemistry, chemical reactions are classified according to different criteria.

1. By changing the oxidation state to redox, which go with a change in the oxidation state of the elements and acid-base, which proceed without changing the oxidation states.

2. By the nature of the process.

Decomposition reactions are chemical reactions in which simple molecules are formed from more complex ones.

Connection reactions chemical reactions are called, in which complex compounds are obtained from several simpler ones.

Substitution reactions are chemical reactions in which an atom or group of atoms in a molecule is replaced by another atom or group of atoms.

Exchange reactions called chemical reactions that occur without changing the oxidation state of the elements and leading to the exchange of constituent parts of the reagents.

3. If possible, proceed in the opposite direction to reversible and irreversible.

Some reactions, such as the combustion of ethanol, are practically irreversible, i.e. it is impossible to create conditions for it to flow in the opposite direction.

However, there are many reactions that, depending on the process conditions, can proceed both in the forward and reverse directions. Reactions that can proceed in both the forward and reverse directions are called reversible.

4. According to the type of bond rupture - homolytic(equal gap, each atom gets one electron) and heterolytic(unequal gap - one gets a pair of electrons).

5. According to the thermal effect, exothermic(heat release) and endothermic(heat absorption).

Combination reactions will generally be exothermic reactions, while decomposition reactions will be endothermic. A rare exception is the endothermic reaction of nitrogen with oxygen N 2 + O 2 = 2NO - Q.

6. According to the state of aggregation of the phases.

homogeneous(the reaction takes place in one phase, without interfaces; reactions in gases or in solutions).

Heterogeneous(reactions taking place at the phase boundary).

7. By using a catalyst.

A catalyst is a substance that speeds up a chemical reaction but remains chemically unchanged.

catalytic practically do not go without the use of a catalyst and non-catalytic.

Classification of organic reactions

Reaction type	Radical	Nucleophilic (N)	Electrophilic (e)
Substitution (S)	radical substitution (S R)	Nucleophilic substitution (S N)	Electrophilic substitution (S E)
Connection (A)	radical connection (A R)	Nucleophilic addition (A N)	Electrophilic addition (A E)
Cleavage (E) (elimination)	radical cleavage (E R)	Nucleophilic cleavage (E N)	Electrophilic elimination (E E)

Electrophilic refers to heterolytic reactions of organic compounds with electrophiles - particles that carry a whole or fractional positive charge. They are subdivided into electrophilic substitution and electrophilic addition reactions. For example,

H 2 C \u003d CH 2 + Br 2  BrCH 2 - CH 2 Br

Nucleophilic refers to heterolytic reactions of organic compounds with nucleophiles - particles that carry an integer or fractional negative charge. They are subdivided into nucleophilic substitution and nucleophilic addition reactions. For example,

CH 3 Br + NaOH  CH 3 OH + NaBr

Radical (chain) reactions are called chemical reactions involving radicals, for example