All chemical reactions in inorganic chemistry. Preparation for the EGE "Classification of chemical reactions in inorganic and organic chemistry" lesson plan in chemistry (grade 11) on the topic

Topics of the Unified State Examination codifier: Classification of chemical reactions in organic and inorganic chemistry.

Chemical reactions - this is a type of interaction of particles when one chemical substance produces another that differs from them in properties and structure. Substances that enter in reaction - reagents. Substances that are 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. Let's consider the main types of classification of chemical reactions.

Classification according to the number and composition of reacting substances

Based on the composition and number of reacting substances, reactions that occur without changing the composition of substances are divided into reactions that occur with a change in the composition of substances:

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

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

S orthorhombic → S monoclinic.

IN organic chemistry such reactions include isomerization reactions , when from one isomer, under the influence of a catalyst and external factors, another is obtained (usually 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 that occur with a change in composition

• Compound reactions (A + B + ... → D)- these are reactions in which one new complex substance is formed from two or more substances. IN inorganic chemistry Compound reactions include combustion reactions of simple substances, the interaction of basic oxides with acidic ones, etc. In organic chemistry such reactions are called reactions accessions Addition reactions — These are reactions in which another molecule is added 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 to form a long chain), etc.

For example, hydration:

CH 2 =CH 2 + H 2 O → CH 3 -CH 2 -OH

• Decomposition reactions (A → B+C+…)- these are reactions during 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, during decomposition hydrogen peroxide:

2H2O2→ 2H 2 O + O 2 .

In organic chemistry separate decomposition reactions and elimination reactions . Elimination reactions — These are reactions during which atoms or atomic groups are separated 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, the name of such reactions contains the prefix “de”. Decomposition reactions in organic chemistry usually involve the breaking of a carbon chain.

For example, reaction butane cracking(splitting into simpler molecules by heating or under the influence of a catalyst):

C 4 H 10 → C 2 H 4 + C 2 H 6

• Substitution reactions - these are reactions during 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 occur according to the following scheme:

AB + C = AC + B.

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

2KI + Cl 2 → 2KCl + I 2.

Both individual atoms and molecules can be replaced.

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

Na 2 CO 3 + SiO 2 → Na 2 SiO 3 + CO 2

IN organic chemistry Substitution reactions are reactions in which part of an organic molecule replaced to other particles. In this case, the substituted particle, as a rule, combines with 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 interaction products, this reaction is more similar to an exchange reaction. Nevertheless, by mechanism such a reaction is a replacement reaction.

• Exchange reactions - these are reactions during which two complex substances exchange their constituent parts:

AB + CD = AC + BD

Exchange reactions include ion exchange reactions, flowing in solutions; reactions illustrating the acid-base properties of substances and others.

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

NaOH + HCl = NaCl + H2O

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

CH 3 -CH 2 -Cl + KOH = CH 3 -CH 2 -OH + KCl

Classification of chemical reactions according to changes in the oxidation state of elements forming substances

By changing the oxidation state of elements chemical reactions are divided into redox reactions, and the reactions going on without changing oxidation states chemical elements.

• Redox reactions (ORR) are reactions during which oxidation states substances change. In this case an exchange takes place electrons.

IN inorganic chemistry Such reactions usually include reactions of decomposition, substitution, combination, and all reactions involving simple substances. To equalize the ORR, the method is used electronic balance(the number of electrons given must be equal to the number received) or electron-ion balance method.

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

Oxidation reactions in organic chemistry are reactions during 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=O + H 2 O + Cu

Recovery reactions in organic chemistry, these are reactions during 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=O + H 2 → CH 3 -CH 2 -OH

• Protolytic and metabolic reactions - These are reactions during which the oxidation states of atoms do not change.

For example, neutralization caustic soda nitric acid:

NaOH + HNO 3 = H 2 O + NaNO 3

Classification of reactions by thermal effect

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

Exothermic reactions - these are reactions accompanied by the release of energy in the form of heat (+ Q). Such reactions include almost all compound reactions.

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

N 2 + O 2 = 2NO – Q

Gaseous reaction hydrogen with hard iodine Also endothermic:

H 2 + I 2 = 2HI – Q

Exothermic reactions that produce light are called reactions burning.

For example, methane combustion:

CH 4 + O 2 = CO 2 + H 2 O

Also exothermic are:

Endothermic reactions are reactions accompanied by energy absorption in the form of heat ( — Q ). As a rule, most reactions occur 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 occur only when heated;
• reactions that occur onlyat very high temperatures or under the influence of an electrical discharge.

For example, conversion of oxygen to ozone:

3O 2 = 2O 3 - Q

IN organic chemistry With the absorption of heat, decomposition reactions occur. 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 the reacting substances (according to phase composition)

Substances can exist in three main states of aggregation - hard, liquid And gaseous. By phase state share reactions homogeneous And heterogeneous.

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

For example, oxidation sulfur dioxide:

2SO 2 (g) + O 2 (g) = 2SO 3 (g)

• Heterogeneous reactions - these 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 contact boundary. Such 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) = CaCO 3 (tv) + H 2 O

To classify reactions by 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 metal crystal lattice, usually hard 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 a specific reaction and the physical properties of the substance.

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

CH 4 (g) + H2O (g) = CO (g) + 3H 2 (g)

Thus, steam reform 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 catalyst action diagram TO when substances interact 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 - these are reactions that occur with the participation of catalysts. For example, the decomposition of Berthollet salt: 2KClO 3 → 2KCl + 3O 2.
• Non-catalytic reactions - These are reactions that occur without the participation of a catalyst. For example, ethane combustion: 2C 2 H 6 + 5O 2 = 2CO 2 + 6H 2 O.

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

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

Classification of reactions by direction

Reversible reactions - these are reactions that can occur in both the forward and reverse directions, i.e. when, under given conditions, 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; production and decomposition of carbonates and bicarbonates, etc.

Irreversible reactions - these are reactions that proceed predominantly in one direction, i.e. The reaction products cannot react with each other under these conditions. Examples of irreversible reactions: combustion; explosive reactions; reactions that occur with the formation of gas, precipitate or water in solutions; dissolution of alkali metals in water; and etc.

Lesson objectives. Generalize the idea of ​​a chemical reaction as the process of converting one or more initial reagent substances into substances that differ from them in chemical composition or structure - reaction products. Consider some of the numerous 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 between 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 a change in substances in which old chemical bonds are broken and new chemical bonds are formed between 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) decomposition (slide 4)
Decomposition reactions in organic chemistry, in contrast to decomposition reactions in inorganic chemistry, have their own specifics. They can be considered as processes inverse to addition, since they most often result in the formation of multiple bonds or cycles.
b) connections (slide 5)
In order to enter into an addition reaction, an organic molecule must have a multiple bond (or cycle), this molecule will be the main one (substrate). A simpler molecule (often an inorganic substance, a reagent) is added at the site where the multiple bond is broken or the ring opens.
c) substitutions (slide 6)
Their distinguishing feature is the interaction of a simple substance with a complex one. Such reactions also exist in organic chemistry.
However, the concept of “substitution” in organic chemistry 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 of 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 suggests reactions from inorganic and organic chemistry. Compound 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. In 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 forming reagents and products (slide 12)
a) redox
b) without changing the oxidation state
Redox reactions in inorganic chemistry include all substitution reactions and those decomposition and combination reactions in which at least one simple substance is involved. In a more generalized version (including organic chemistry): all reactions involving simple substances. Conversely, reactions that occur without changing the oxidation states of the elements that form the reactants and reaction products include all exchange reactions.

Reinforcing the topic studied (slides 13-21).

Lesson summary.

Lesson objectives. 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 of organic compounds. Analyze the structure of the carboxyl group and predict the chemical behavior of carboxylic acids. Consider the general properties of carboxylic acids in comparison with the properties of mineral acids. Give an idea of ​​the special properties of carboxylic acids (reactions at radicals and the formation of functional derivatives). Introduce students to the most characteristic representatives of carboxylic acids and show their importance in nature and in human life.

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

Carboxylic acids are classified:
Based on the number of carboxyl groups, carboxylic acids are 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 bonded, 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 = CH – CH 2 – COOH Butene-3-oic acid (vinylacetic acid)
CH 3 – CH = CH – COOH Butene-2-oic acid (crotonic acid)

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

Structure(Slide 6)
The carboxyl group COOH consists of a carbonyl group C=O and a 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 the O-H bond is weakened:

In turn, the OH group “quenches” 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. As the relative molecular weight increases, the solubility of acids in water decreases and the boiling point increases. 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 COOCH 2 CH 3 + H 2 O

6) Interaction with ammonia:
CH 3 COOH + NH 3 CH 3 COONH 4
When ammonium salts of carboxylic acids are heated, their amides are formed:
CH 3 COONH 4 CH 3 CONH 2 + H 2 O
7) Under the influence 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 methyl ester of propanoic acid
CH 3 – CO – O – CH 2 – CH 3 ethyl ester of ethanoic acid
C3H 7 – COOH butanoic acid

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

2. Another common method is the hydrolysis of halogenated hydrocarbons containing three halogen atoms per carbon atom:

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

4. Hydrolysis of esters:

5. Hydrolysis of acid anhydrides:

Methods for producing carboxylic acids
For individual acids There are specific methods of obtaining (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 the catalytic oxidation of butane with atmospheric oxygen:

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

Application of carboxylic acids(Slide 12)

Reinforcing the topic studied (slide 13-14).

>> Chemistry: Types of chemical reactions in organic chemistry

Reactions of organic substances can be formally divided into four main types: substitution, addition, elimination (elimination) and rearrangement (isomerization). It is obvious that the entire variety of reactions of organic compounds cannot be reduced to the framework of the proposed classification (for example, combustion reactions). However, such a classification will help to establish analogies with the classifications of reactions occurring between inorganic substances that are already familiar to you from the course of inorganic chemistry.

Typically, the main organic compound involved in a reaction is called the substrate, and the other component of the reaction is conventionally considered the reactant.

Substitution reactions

Reactions that result in the replacement of one atom or group of atoms in the original molecule (substrate) with other atoms or groups of atoms are called substitution reactions.

Substitution reactions involve saturated and aromatic compounds, such as, for example, alkanes, cycloalkanes or arenes.

Let us give examples of such reactions.

Classification of chemical reactions in inorganic and organic chemistry

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

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

Chemical reactions must 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 a different matter - 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 any of these characteristics can include reactions between both inorganic and organic substances.

Let's consider the classification of chemical reactions according to various criteria.

Classification of chemical reactions according to the number and composition of reactants. Reactions that occur 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:

$С_((graphite))⇄С_((diamond))$

$S_((rhombic))⇄S_((monoclinic))$

$Р_((white))⇄Р_((red))$

$Sn_((white tin))⇄Sn_((gray tin))$

$3О_(2(oxygen))⇄2О_(3(ozone))$.

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

1. Isomerization of alkanes.

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

2. Isomerization of alkenes.

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

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

5. Isomerization of ammonium cyanate by heating.

Urea was first synthesized by F. Wöhler in 1882 by isomerizing ammonium cyanate when heated.

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

Four types of such reactions can be distinguished: combination, decomposition, substitution and exchange.

1. Compound reactions- These are 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 using the example of reactions for the production of sulfuric acid from sulfur:

1) obtaining sulfur oxide (IV):

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

2) obtaining 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:

$SO_3+H_2O=H_2SO_4$ - two complex substances form one complex substance.

An example of a compound reaction in which one complex substance is formed from more than two initial substances is the final stage of producing nitric acid:

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

In organic chemistry, joining reactions are commonly called addition reactions. The whole variety of such reactions can be considered using 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 producing oxygen by laboratory methods:

1) decomposition of mercury (II) oxide:

$2HgO(→)↖(t°)2Hg+O_2$ - two simple ones 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 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) dehydration reaction (elimination of water) of ethanol:

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

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

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

3) propane cracking reaction:

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

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

In inorganic chemistry, an example of such processes is a block of reactions characterizing the properties, for example, of 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 the 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 of saturated compounds, in particular methane, the ability of its hydrogen atoms to be replaced by halogen atoms:

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

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

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

$CHCl_3+Cl_2→(CCl_4)↙(carbon tetrachloride)+HCl$.

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 a 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 in solutions proceed according to Berthollet’s rule, i.e. only if the result is the formation of a precipitate, gas or slightly dissociating substance (for example, $H_2O$).

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

1) neutralization reaction that occurs 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 occurs 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 occurs 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, we can consider a block of reactions that characterize, for example, the properties of acetic acid:

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

$CH_3COOH+NaOH⇄NaCH_3COO+H_2O$

$CH_3COOH+OH^(-)⇄CH_3COO^(-)+H_2O$;

2) reaction that occurs with the formation of gas:

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

3) reaction that occurs 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 changes in oxidation states of chemical elements forming 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 is involved, 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.$(2Mg)↖(0)+(O_2)↖(0)=(2Mg)↖(+2)(O)↖(-2)$

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

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

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, a striking example of redox reactions is the properties of aldehydes:

1. Aldehydes are reduced to the corresponding alcohols:

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

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

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

2. Aldehydes are oxidized into the corresponding acids:

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

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

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

Reactions that occur 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

Based on the thermal effect, reactions are divided into exothermic and endothermic.

Exothermic reactions.

These reactions occur with the release of energy.

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

$N_2+O_2=2NO - Q$,

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

Exothermic reactions that occur with the release of light are classified as combustion reactions, for example:

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

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

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 occur with the absorption of energy.

Obviously, these include almost all decomposition reactions, for example:

a) calcination of limestone:

$CaCO_3(→)↖(t°)CaO+CO_2-Q;$

b) butane cracking:

The amount of energy released or absorbed as a result of a reaction is called thermal effect of 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 the 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):

$2Al_((t))+3CuCl_(2(sol))=3Cu_((t))+2AlCl_(3(sol))$,

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

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 occur 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 are in progress with the participation of 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 occur with the participation of special biological catalysts of a protein nature - enzymes, they are all 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 only in one direction.

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

Reversible reactions.

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

The overwhelming majority of such reactions are.

In organic chemistry, the sign of reversibility is reflected by the antonyms of the processes:

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

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

When chemical reactions occur, some bonds break and others form. Chemical reactions are conventionally divided into organic and inorganic. Organic reactions are considered to be reactions in which at least one of the reactants is an organic compound that changes its molecular structure during the reaction. The difference between organic reactions and inorganic ones is that, as a rule, molecules are involved in them. The rate of such reactions is low, and the product yield is usually only 50-80%. To increase the reaction rate, catalysts are used and the temperature or pressure is increased. Next, we will consider the types of chemical reactions in organic chemistry.

Classification by the nature of chemical transformations

• Substitution reactions
• Addition reactions
• Isomerization reaction and rearrangement
• Oxidation reactions
• Decomposition reactions

Substitution reactions

During substitution reactions, one atom or group of atoms in the initial molecule is replaced by other atoms or groups of atoms, forming a new molecule. As a rule, such reactions are characteristic of saturated and aromatic hydrocarbons, for example:

Addition reactions

When addition reactions occur, one molecule of a new compound is formed from two or more molecules of substances. Such reactions are typical for unsaturated compounds. There are reactions of hydrogenation (reduction), halogenation, hydrohalogenation, hydration, polymerization, etc.:

1. Hydrogenation– addition of a hydrogen molecule:

Elimination reaction

As a result of elimination reactions, organic molecules lose atoms or groups of atoms, and a new substance is formed containing one or more multiple bonds. Elimination reactions include reactions dehydrogenation, dehydration, dehydrohalogenation and so on.:

Isomerization reactions and rearrangement

During such reactions, intramolecular rearrangement occurs, i.e. the transition of atoms or groups of atoms from one part of the molecule to another without changing the molecular formula of the substance participating in the reaction, for example:

Oxidation reactions

As a result of exposure to an oxidizing reagent, the oxidation state of carbon in an organic atom, molecule or ion increases due to the loss of electrons, resulting in the formation of a new compound:

Condensation and polycondensation reactions

Consists in the interaction of several (two or more) organic compounds with the formation of new C-C bonds and a low molecular weight compound:

Polycondensation is the formation of a polymer molecule from monomers containing functional groups with the release of a low molecular weight compound. Unlike polymerization reactions, which result in the formation of a polymer having a composition similar to the monomer, as a result of polycondensation reactions, the composition of the resulting polymer differs from its monomer:

Decomposition reactions

This is the process of breaking down a complex organic compound into less complex or simple substances:

C 18 H 38 → C 9 H 18 + C 9 H 20

Classification of chemical reactions by mechanisms

Reactions involving the rupture of covalent bonds in organic compounds are possible by two mechanisms (i.e., a path leading to the rupture of an old bond and the formation of a new one) – heterolytic (ionic) and homolytic (radical).

Heterolytic (ionic) mechanism

In reactions proceeding according to the heterolytic mechanism, intermediate particles of the ionic type with a charged carbon atom are formed. Particles carrying a positive charge are called carbocations, and negative ones are called carbanions. In this case, it is not the breaking of the common electron pair that occurs, but its transition to one of the atoms, with the formation of an ion:

Strongly polar, for example H–O, C–O, and easily polarizable, for example C–Br, C–I bonds exhibit a tendency to heterolytic cleavage.

Reactions proceeding according to the heterolytic mechanism are divided into nucleophilic and electrophilic reactions. A reagent that has an electron pair to form a bond is called nucleophilic or electron-donating. For example, HO - , RO - , Cl - , RCOO - , CN - , R - , NH 2 , H 2 O , NH 3 , C 2 H 5 OH , alkenes, arenes.

A reagent that has an unfilled electron shell and is capable of attaching a pair of electrons in the process of forming a new bond. The following cations are called electrophilic reagents: H +, R 3 C +, AlCl 3, ZnCl 2, SO 3, BF 3, R-Cl, R 2 C=O

Nucleophilic substitution reactions

Characteristic for alkyl and aryl halides:

Nucleophilic addition reactions

Electrophilic substitution reactions

Electrophilic addition reactions

Homolytic (radical mechanism)

In reactions proceeding according to the homolytic (radical) mechanism, at the first stage the covalent bond is broken with the formation of radicals. The resulting free radical then acts as an attacking reagent. Bond cleavage by a radical mechanism is typical for non-polar or low-polar covalent bonds (C–C, N–N, C–H).

Distinguish between radical substitution and radical addition reactions

Radical displacement reactions

Characteristic of alkanes

Radical addition reactions

Characteristic of alkenes and alkynes

Thus, we examined the main types of chemical reactions in organic chemistry