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Types of bonds in organic chemistry. Electronic structure of organic compounds How to count bonds in organic chemistry

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1. Hybridization of carbon atomic orbitals

Atomic orbital is a function that describes the density of the electron cloud at each point in space around the nucleus of an atom. An electron cloud is a region of space in which an electron can be detected with a high probability.

To harmonize the electronic structure of the carbon atom and the valence of this element, concepts about the excitation of the carbon atom are used. In the normal (unexcited) state, the carbon atom has two unpaired 2 r 2 electrons.

In an excited state (when energy is absorbed) one of 2 s 2 electrons can go to free r-orbital. Then four unpaired electrons appear in the carbon atom. On the second energy level except 2 s-there are three orbitals 2 r-orbitals. These 2 r-orbitals have an ellipsoidal shape, similar to dumbbells, and are oriented in space at an angle of 90° to each other. 2 r-Orbitals denote 2 r X, 2r y and 2 r z in accordance with the axes along which these orbitals are located.

When chemical bonds are formed, the electron orbitals acquire the same shape.

Thus, in saturated hydrocarbons one s-orbital and three r-orbitals of the carbon atom to form four identical (hybrid) sr 3-orbitals:

This - sr 3 -hybridization.

Hybridization- alignment (mixing) of atomic orbitals ( s And r) with the formation of new atomic orbitals called hybrid orbitals.

TETRAHEDRON (angles = 109°28?

sr 2 -Hybridization- mixing one s- and two r-orbitals. As a result, three hybrids are formed sr 2 -orbitals.

These sr 2-orbitals are located in the same plane (with axes X, at) and are directed to the vertices of the triangle with an angle between the orbitals of 120°.

Unhybridized r-the orbital is perpendicular to the plane of the three hybrid sr 2-orbitals (oriented along the axis z).

Upper half r-orbitals are above the plane, the lower half is below the plane.

Type sr 2-carbon hybridization occurs in compounds with a double bond:

C=C, C=O, C=N.

Moreover, only one of the bonds between two atoms (for example, C=C) can be an - bond. (The other bonding orbitals of the atom point in opposite directions.)

The second bond is formed as a result of overlapping non-hybrid r-orbitals on both sides of the line connecting the atomic nuclei.

Covalent bond formed by lateral overlap r-orbitals of neighboring carbon atoms is called pi( r)-connection .

sr-Hybridization s- and one r sr-orbitals. sr-The orbitals are located on the same line (at an angle of 180°) and directed in opposite directions from the nucleus of the carbon atom. Two r at- connections. In the picture sr-orbitals are shown along the axis y, and the unhybridized two r-orbitals- along axes X And z.

A carbon-carbon triple bond, C?C, consists of a y-bond that occurs when sp-hybrid orbitals, and two p-bonds.

2. Reactions of electrophilic substitution of hydrogen atoms in the benzene series

1. Halogenation reaction. The halogenation reaction of the benzene ring is carried out in the presence of catalysts (most often iron or aluminum halides). The role of the catalyst is to form a highly polarized complex with a halogen: FORMULA. The leftmost chlorine atom in the complex becomes electron unsaturated as a result of polarization of the Cl - Cl bond and is capable of interacting with nucleophilic reagents (in this case, benzene):

d - the complex abstracts a proton and turns into a substitution product (chlorobenzene). The proton interacts with - with the regeneration of aluminum chloride, forming hydrogen chloride:

In the case of an excess of halogen, di- and polyhalogen-substituted compounds can be obtained, up to the complete replacement of all hydrogen atoms in benzene.

Direct iodination in the aromatic ring cannot be carried out due to the low reactivity of iodine. Direct fluoridation aromatic hydrocarbons proceeds so vigorously that a complex mixture of products is formed, in which the target fluorinated derivatives are contained in small quantities. Depending on the conditions of the halogenation reaction of alkylbenzenes, a halogen can replace hydrogen atoms in the benzene ring (“in the cold” in the presence of Lewis acids) or in the side chain (when heated or in the light). In the latter case, the reaction proceeds by a free radical mechanism, similar to the substitution mechanism in alkanes.

2. Nitration reaction. Benzene reacts slowly with concentrated nitric acid. The rate of nitration increases significantly if the nitration reaction is carried out with a mixture of concentrated nitric and sulfuric acids (usually in a ratio of 1:2); this mixture is called nitrating.

The process occurs due to the fact that sulfuric acid, being stronger, protonates nitric acid, and the resulting protonated particle decomposes into water and an active electrophilic reagent - nitronium cation (nitronium cation).

The nitration reaction of benzene is an electrophilic substitution reaction and is ionic in nature. First, a p-complex is formed as a result of the interaction of electrons of the benzene ring with a positively charged particle of the nitronium cation.

Then the transition of the p-complex to the y-complex occurs. In this case, two p-electrons out of six go to the formation of a covalent bond C-NO2+. The remaining four -electrons are distributed among the five carbon atoms of the benzene ring. A y-complex is formed in the form of an unstable carbocation.

The unstable y-complex, under the influence of the HSO4- ion, loses a proton to form the aromatic structure of nitrobenzene.

3. Sulfonation reaction. To introduce a sulfo group into the benzene ring, fuming sulfuric acid is used, i.e., containing an excess of sulfuric anhydride (SO3). The electrophilic particle is SO3. The mechanism of sulfonation of aromatic compounds includes the following stages:

4. Alkylation reaction according to Friedel-Crafts. The role of the catalyst (usually AlCl3) in this process is to enhance the polarization of the alkyl halide to form a positively charged species that undergoes an electrophilic substitution reaction: FORMULA

3. Anthracene: structure and main chemical properties

Anthracene - a compound whose molecule consists of three aromatic rings lying in the same plane. It is obtained from the anthracene fraction of coal tar, boiling at 300...350 °C. In laboratory practice, anthracene can be obtained

a) according to the Friedel-Crafts reaction:

b) according to the Fittig reaction:

In the anthracene molecule, the ninth and tenth positions, which are under the influence of the two outer rings, are the most active. Anthracene easily undergoes addition reactions at these positions:

When exposed to oxidizing agents, anthracene easily forms anthraquinone, which is widely used for the synthesis of dyes:

4. Conjugated dienes and methods for their synthesis

Diene hydrocarbons (dienes) are unsaturated hydrocarbons having two double bonds, the general formula CnH2n-2.

The two double bonds in a hydrocarbon molecule can be arranged in different ways. If they are concentrated at one carbon atom, they are called cumulated: -C=C=C- If two double bonds are separated by one simple bond, they are called conjugated: -C=C - C=C- If double bonds are separated by two or more simple bonds bonds, then they are called isolated: -C=C- (CH2)n - C=C-

5. Rules for orientation in the benzene ring

When studying substitution reactions in the benzene ring, it was discovered that if it already contains a substituent, then, depending on its nature, the second one enters a certain position. Thus, each substituent on the benzene ring exhibits a specific directing or orienting effect. The position of the newly introduced substituent is also influenced by the nature of the substituent itself, i.e., whether the active reagent has an electrophilic or nucleophilic nature. All substituents, by the nature of their directing action in are divided into two groups.

Substituents of the first kind direct the introduced group to ortho- and para-positions:

Substituents of this kind include the following groups, arranged in descending order of their orienting strength: N(CH3)2, NH2, OH, CH3 and other alkyls, as well as Cl, Br, I.

Substituents of the second kind V electrophilic substitution reactions direct the input groups to the meta position. Substituents of this type include the following groups: - NO2, - CN, - SO3H, - CHO, - COOH.

6. The nature of the double bond and chemical properties of ethylene compounds

According to modern concepts, the two bonds connecting two unsaturated carbon atoms are not the same: one of them is a y-bond, and the other a p-bond. The latter bond is less strong and is “broken” during addition reactions.

The inequality of two bonds in unsaturated compounds is indicated, in particular, by comparing the energies of formation of single and double bonds. The energy of formation of a single bond is 340 kJ/mol (about 82 kcal/mol), and a double bond is 615 kJ/mol (about 147 kcal/mol). Naturally, it takes less energy to break a p-bond than to break a y-bond. Thus, the fragility of a double bond is explained by the fact that one of the two bonds forming a double bond has a different electronic structure than ordinary - bonds and is less strong.

Names of olefins usually derived from the names of the corresponding saturated hydrocarbons, but the ending is en replaced by the ending - Ilen. According to the international nomenclature, instead of ending - Ilen olefins are given a shorter ending - en.

Isomerism olefins depends on the isomerism of the chain of carbon atoms, i.e., on whether the chain is straight or branched, and on the position of the double bond in the chain. There is also a third reason for the isomerism of olefins: the different arrangement of atoms and atomic groups in space, i.e. stereoisomerism. Isomerism, depending on the different arrangement in space of atoms and atomic groups, is calledspatial isomerism , orstereoisomerism .

Geometric , orcis- Andtrans isomerism , is a type of spatial isomerism depending on different locations atoms relative to the plane of the double bond.

To indicate the location of the double bond (as well as branches in the chain), according to the international IUPAC nomenclature, the carbon atoms of the longest chain are numbered, starting from the end to which the double bond is closest. Thus, the two straight-chain isomers of butylene will be called butene-1 and butene-2:

1. Hydrogenation reaction. Unsaturated hydrocarbons easily add hydrogen at the double bond in the presence of catalysts 67 (Pt, Pd, Ni). With Pt or Pd catalyst the reaction occurs at 20...100 °C, with Ni - at more high temperatures:

2. Halogenation reaction. Alkenes under normal conditions add halogens, especially chlorine and bromine. As a result, dihalogen derivatives of alkanes are formed containing halogens at neighboring carbon atoms, the so-called vicinal dihaloalkanes: CH

3CH=CH2 + Cl2> CH3CHClCH2Cl

3. Reaction of addition of hydrogen halides. Hydrohalogenation

4. Alkene hydration reaction. Under normal conditions, alkenes do not react with water. But in the presence of catalysts, under heat and pressure, they add water and form alcohols:

5. Reaction of addition of sulfuric acid. The interaction of alkenes with sulfuric acid proceeds similarly to the addition of hydrogen halides. As a result, acidic esters of sulfuric acid are formed:

6. Alkylation reaction of alkenes. Catalytic addition of alkanes with a tertiary carbon atom to alkenes is possible (catalysts - H2SO4, HF, AlCl3 and BF3):

7. Alkene oxidation reaction. Alkenes are easily oxidized. Depending on the oxidation conditions, different products are formed. When burned in air, alkenes are converted to carbon dioxide and water: CH2 = CH2 + 3O2 > 2CO2 + 2H2O.

When alkenes react with atmospheric oxygen in the presence of a silver catalyst, organic oxides are formed:

Acyl hydroperoxides act similarly on ethylene (Prilezhaev reaction):

One of the most characteristic oxidation reactions is the interaction of alkenes with a weakly alkaline solution of potassium permanganate KMnO4 with the formation of dihydric alcohols - glycols (Wagner reaction). The reaction proceeds in the cold as follows:

Concentrated solutions of oxidizing agents (potassium permanganate in an acidic environment, chromic acid, nitric acid) break the alkene molecule at the double bond to form ketones and acids:

8. Ozonation reaction of alkenes. It is also widely used to determine the structure of alkenes:

9. Substitution reactions. Alkenes are also capable of substitution reactions under certain conditions. Thus, during high-temperature (500...550 °C) chlorination of alkenes, hydrogen is replaced in the allylic position:

10. Alkene polymerization reaction

CH2 = CH2 > (-CH2 - CH2 -) n it turns out to be polyethylene

11. Isomerization reaction. At high temperatures or in the presence of catalysts, alkenes are capable of isomerizing, which either changes the structure of the carbon skeleton or moves the double bond:

7. Naphthalene and its structure. Hückel's rule

Naphthalene hydrocarbons are the main aromatic hydrocarbon of coal tar. There are a large number of polycyclic aromatic compounds in which the benzene rings share ortho carbon atoms. The most important of them are naphthalene, anthracene and phenanthrene. In anthracene, the rings are connected linearly, while in phenanthrene they are connected at an angle, unlike the benzene molecule, not all bonds in the naphthalene core have the same length:

Hückel's rule : aromatic is a planar monocyclic conjugated system containing (4n + 2) p-electrons (where n = 0,1,2...).

Thus, planar cyclic conjugated systems containing 2, 6, 10, 14, etc. will be aromatic. p-electrons.

8. Alkynes and sp-hybridization of the carbon atom. Methods for producing alkynes

Hydrocarbons of the acetylene series have the general formula

WITH n H2 n-2

The first simplest hydrocarbon in this series is acetylene C2H2. The structural formula of acetylene, like other hydrocarbons of this series, contains a triple bond:

N - S? S - N.

sr-Hybridization- this is mixing (alignment in shape and energy) of one s- and one r-orbitals to form two hybrid sr-orbitals. sr-The orbitals are located on the same line (at an angle of 180°) and directed in opposite directions from the nucleus of the carbon atom.

Two r-orbitals remain unhybridized. They are placed mutually perpendicular to the directions at- connections.

In the picture sr-orbitals are shown along the axis y, and the unhybridized two r-orbitals- along axes X And z.

The triple carbon-carbon bond C?C consists of a y-bond, which arises when sp-hybrid orbitals overlap, and two p-bonds.

Calcium carbide is produced on an industrial scale by heating coal in electric ovens with quicklime at a temperature of about 2500 °C according to the reaction

CaO + 3C > CaC2 + CO.

If calcium carbide is exposed to water, it rapidly decomposes with the release of gas - acetylene:

A newer industrial method for producing acetylene is the pyrolysis of hydrocarbons, in particular methane, which at 1400 °C gives a mixture of acetylene with hydrogen:

2CH4>H-C=C-H + 3H2.

1. Dehydrohalogenation of vicinal dihaloalkanes

2. Reaction of sodium acetylenides with primary alkyl halides:

3. Dehalogenation of vicinal tetrahaloalkanes:

9. Preparation methods and chemicalsproperties of alcohols

Alcohols are derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by the corresponding number of hydroxyl groups (-OH).

General formula of alcohols

where R is an alkyl or substituted alkyl group.

The nature of the radical R to which the hydroxyl group is associated determines the saturated or unsaturated state of alcohols, and the number of hydroxyl groups determines its atomicity: alcohols are monoatomic, diatomic, triatomic and polyatomic.

Preparation: 1. Hydration of alkenes

2. Enzymatic hydrolysis of carbohydrates. Enzymatic hydrolysis of sugars by yeast - the most ancient synthetic chemical process - is still of great importance for the production of ethyl alcohol.

When using starch as a starting material, in addition to ethyl alcohol, fusel oil is also formed (in smaller quantities), which is a mixture of primary alcohols, mainly isopentyl, isopropyl and isobutyl.

3. Synthesis of methyl alcohol:

4. Reaction of hydroboration-oxidation of alkenes:

5. Syntheses of alcohols using the Grignard reagent:

Properties: The chemical properties of alcohols are determined by both the structure of the alkyl radical and the reactive hydroxyl group. Reactions involving the hydroxyl group can occur either with the cleavage of the C-OH bond (360 kJ/mol) or with the cleavage O-N connections(429 kJ/mol) A. C-OH bond cleavage

1. Reaction with hydrogen halides:

ROH + HX >RX + H2O.

Reactivity decreases in the series: HI > HBr > HCl

2. Reaction with phosphorus trihalides:

3. Dehydration of alcohols in the presence of water-removing agents:

B. Disconnection HE

4. Reaction of alcohols with metals(Na, K, Mg, Al)

5. Formation of esters:

Esterification reaction

6. Oxidation reactions When alcohols are oxidized with a chromium mixture or KMnO4 in a sulfuric acid solution, the composition of the products depends on the nature of the carbon atom (primary, secondary or tertiary) to which the hydroxyl group is associated: primary alcohols form aldehydes, secondary alcohols form ketones.

9. Alkadienes and methods for their preparation

Diene hydrocarbons (dienes) are unsaturated hydrocarbons having two double bonds with the general formula

The two double bonds in a hydrocarbon molecule can be arranged in different ways.

If they are concentrated at one carbon atom, they are called cumulated:

If two double bonds are separated by one single bond, they are called conjugate:

If double bonds are separated by two or more simple bonds, then they are called isolated: -C=C- (CH2)n - C=C-

Dienes are usually prepared by the same methods as simple alkenes. For example, the most important diene, butadiene-1,3 (used to produce synthetic rubber), is obtained in the USA by dehydrogenation of butane:

In the USSR, industrial synthesis of 1,3 butadiene was used according to the method of S.V. Lebedev (1933) from ethyl alcohol at 400...500 °C over a MgO-ZnO catalyst:

The reaction includes the following stages: dehydrogenation of the alcohol to an aldehyde, aldol condensation of acetaldehyde, reduction of the aldol to 1,3-butanediol, and finally dehydration of the alcohol:

10. Electronegativity of elements and types of chemical bonds

Electronegativity (h) (relative electronegativity) is a fundamental chemical property of an atom, a quantitative characteristic of the ability of an atom in a molecule to displace common electron pairs toward itself, that is, the ability of atoms to attract electrons of other atoms.

The highest degree of electronegativity is for halogens and strong oxidizing agents (p-elements of group VII, O, Kr, Xe), and the lowest for active metals (s-elements of group I).

Ionic. The electron configuration of an inert gas for any atom can be formed due to the transfer of electrons: atoms of one of the elements give up electrons, which go to the atoms of another element.

In this case, a so-called ionic (electrovalent, heteropolar) bond is formed between these atoms.

This type of bond occurs between atoms of elements that have significantly different electronegativity (for example, between a typical metal and a typical non-metal).

Covalent bond. When atoms of equal (atoms of the same element) or similar electronegativity interact, electron transfer does not occur. The electron configuration of the inert gas for such atoms is formed due to the sharing of two, four or six electrons by the interacting atoms. Each of the shared pairs of electrons forms one covalent (homeopolar) bond:

Covalent bond - most common in organic chemistry connection type. It's quite durable.

A covalent bond and therefore a molecule can be nonpolar when both bonded atoms have the same electron affinity (for example, H:H). It can be polar when an electron pair, due to the greater affinity for the electron of one of the atoms, is pulled towards it:

With this method, the designations + and - mean that the atom with the symbol - has excess electron density, and the atom with the + symbol has slightly reduced electron density compared to isolated atoms.

Donor-acceptor bond. When atoms that have lone electron pairs interact with a proton or another atom that lacks two electrons to form an octet (doublet), the lone electron pair becomes shared and forms a new covalent bond between these atoms.

In this case, the atom that donates electrons is called a donor, and the atom that accepts electrons is called an acceptor:

chemical covalent benzene naphthalene

In the emerging ammonium ion, the covalent bond formed differs from the bonds that existed in the ammonia molecule only in the method of formation; in physical and chemical properties, all four N-H connections absolutely identical.

Semipolar connection. This type of donor-acceptor bond is often found in molecules of organic compounds (for example, in nitro compounds, sulfoxides, etc.).

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Variety of inorganic and organic substances

Organic chemistry is chemistry carbon compounds. Inorganic carbon compounds include: carbon oxides, carbonic acid, carbonates and bicarbonates, carbides. Organic substances other than carbon contain hydrogen, oxygen, nitrogen, phosphorus, sulfur and other elements. Carbon atoms can form long unbranched and branched chains, rings, and attach other elements, so the number of organic compounds is close to 20 million, while Not organic matter there are just over 100 thousand.

The basis for the development of organic chemistry is the theory of the structure of organic compounds by A. M. Butlerov. An important role in describing the structure of organic compounds belongs to the concept of valency, which characterizes the ability of atoms to form chemical bonds and determines their number. Carbon in organic compounds always tetravalent. The main postulate of the theory of A.M. Butlerov is the position on the chemical structure of matter, i.e. chemical bond. This order is displayed using structural formulas. Butlerov's theory states the idea that every substance has specific chemical structure And properties of substances depend on structure.

Theory of the chemical structure of organic compounds by A. M. Butlerov

Just as for inorganic chemistry the basis of development is the Periodic Law and Periodic table chemical elements D.I. Mendeleev, became fundamental for organic chemistry.

Theory of the chemical structure of organic compounds by A. M. Butlerov

The main postulate of Butlerov’s theory is the position on the chemical structure of matter, which means the order, the sequence of mutual connection of atoms into molecules, i.e. chemical bond.

Chemical structure- the order of connection of atoms of chemical elements in a molecule according to their valency.

This order can be displayed using structural formulas in which the valencies of atoms are indicated by dashes: one line corresponds to the unit of valence of an atom of a chemical element. For example, for the organic substance methane, which has the molecular formula CH 4, the structural formula looks like this:

The main provisions of the theory of A. M. Butlerov:

Atoms in organic molecules are bonded to each other according to their valency. Carbon in organic compounds is always tetravalent, and its atoms are capable of combining with each other, forming various chains.

· The properties of substances are determined not only by their qualitative and quantitative composition, but also by the order of connection of atoms in the molecule, i.e. chemical structure substances.

· The properties of organic compounds depend not only on the composition of the substance and the order of connection of atoms in its molecule, but also on mutual influence of atoms and groups of atoms on top of each other.

The theory of the structure of organic compounds is a dynamic and developing doctrine. As knowledge about the nature of chemical bonds and the influence of the electronic structure of molecules of organic substances developed, they began to use, in addition to empirical and structural, electronic formulas. Such formulas show the direction displacement of electron pairs in a molecule.

Quantum chemistry and the chemistry of the structure of organic compounds confirmed the doctrine of the spatial direction of chemical bonds (cis- and trans isomerism), studied the energy characteristics of mutual transitions in isomers, made it possible to judge the mutual influence of atoms in the molecules of various substances, created the prerequisites for predicting the types of isomerism and directions and mechanisms of chemical reactions.

Organic substances have a number of characteristics.

· All organic substances contain carbon and hydrogen, so when burned they form carbon dioxide and water.

Organic matter complexly built and can have a huge molecular weight (proteins, fats, carbohydrates).

· Organic substances can be arranged in rows similar in composition, structure and properties homologues.

· For organic substances it is characteristic isomerism.

Isomerism and homology of organic substances

The properties of organic substances depend not only on their composition, but also on order of connection of atoms in a molecule.

Isomerism- this is the phenomenon of the existence of different substances - isomers with the same qualitative and quantitative composition, i.e. with the same molecular formula.

There are two types of isomerism: structural and spatial(stereoisomerism). Structural isomers differ from each other in the bond order of the atoms in the molecule; stereoisomers - the arrangement of atoms in space with the same order of bonds between them.

Main types of isomerism:

· Structural isomerism - substances differ in the order of bonding of atoms in molecules:

1) isomerism of the carbon skeleton;

2) position isomerism:

multiple bonds;
deputies;
functional groups;

3) isomerism of homologous series (interclass).

· Spatial isomerism - molecules of substances differ not in the order of bonding of atoms, but in their position in space: cis-, trans-isomerism (geometric).

Classification of organic substances

It is known that the properties of organic substances are determined by their composition and chemical structure. Therefore, it is not surprising that the classification of organic compounds is based on the theory of structure - the theory of A. M. Butlerov. Organic substances are classified according to the presence and order of connection of atoms in their molecules. The most durable and least changeable part of the molecule of an organic substance is its skeleton - chain of carbon atoms. Depending on the order of connection of carbon atoms in this chain, substances are divided into acyclic, not containing closed chains of carbon atoms in molecules, and carbocyclic containing such chains (cycles) in molecules.

In addition to carbon and hydrogen atoms, molecules of organic substances can contain atoms of other chemical elements. Substances in whose molecules these so-called heteroatoms are included in a closed chain are classified as heterocyclic compounds.

Heteroatoms(oxygen, nitrogen, etc.) can be part of molecules and acyclic compounds, forming in them functional groups, For example,

hydroxyl

carbonyl

carboxyl

amino group

Functional group- a group of atoms that determines the most characteristic chemical properties of a substance and its belonging to a certain class of compounds.

Nomenclature of organic compounds

At the beginning of the development of organic chemistry, compounds to be discovered were assigned trivial names, often associated with the history of their production: acetic acid (which is the basis of wine vinegar), butyric acid (formed in butter), glycol (i.e. “sweet”), etc. As the number of new discovered substances increased, the need arose to associate names with their structure. This is how rational names appeared: methylamine, diethylamine, ethyl alcohol, methyl ethyl ketone, which are based on the name of the simplest compound. For more complex compounds rational nomenclature is unsuitable.

The theory of structure of A. M. Butlerov provided the basis for the classification and nomenclature of organic compounds according to structural elements and the arrangement of carbon atoms in the molecule. Currently, the most commonly used nomenclature is developed by International Union of Pure and Applied Chemistry (IUPAC), which is called nomenclature IUPAC. IUPAC rules recommend several principles for the formation of names, one of them is the principle of substitution. Based on this, a replacement nomenclature has been developed, which is the most universal. Let us present several basic rules of substitutive nomenclature and consider their application using the example of a heterofunctional compound containing two functional groups - the amino acid leucine:

1. The names of compounds are based on the parent structure (the main chain of an acyclic molecule, a carbocyclic or heterocyclic system). The name of the parent structure forms the basis of the name, the root of the word.

In this case, the parent structure is a chain of five carbon atoms connected by single bonds. Thus, the root part of the name is pentane.

2. Characteristic groups and substituents (structural elements) are designated by prefixes and suffixes. Characteristic groups are divided by seniority. Order of precedence of the main groups:

The senior characteristic group is identified, which is designated in the suffix. All other substituents are named in the prefix in alphabetical order.

In this case, the senior characteristic group is carboxyl, i.e. this compound belongs to the class carboxylic acids, so we add -ic acid to the root part of the name. The second oldest group is the amino group, which is designated by the prefix amino-. In addition, the molecule contains the hydrocarbon substituent methyl-. Thus, the basis of the name is aminomethylpentanoic acid.

3. The name includes the designation of the double and triple bond, which comes immediately after the root.

The compound in question does not contain multiple bonds.

4. The atoms of the parent structure are numbered. Numbering begins from the end of the carbon chain to which the highest characteristic group is located closest:

The numbering of the chain begins with the carbon atom that is part of the carboxyl group, it is assigned the number 1. In this case, the amino group will be at carbon 2, and the methyl group will be at carbon 4.

Thus, the natural amino acid leucine, according to the rules of IUPAC nomenclature, is called 2-amino-4-methylpentanoic acid.

Hydrocarbons. Classification of hydrocarbons

Hydrocarbons- These are compounds consisting only of hydrogen and carbon atoms.

Depending on the structure of the carbon chain, organic compounds are divided into open-chain compounds - acyclic(aliphatic) and cyclic- With closed circuit atoms.

Cyclic ones are divided into two groups: carbocyclic compounds(cycles are formed only by carbon atoms) and heterocyclic(the cycles also include other atoms, such as oxygen, nitrogen, sulfur).

Carbocyclic compounds, in turn, include two series of compounds: alicyclic And aromatic.

Aromatic compounds based on the molecular structure have flat carbon-containing cycles with a special closed system of p-electrons, forming a common π-system (a single π-electron cloud). Aromaticity is also characteristic of many heterocyclic compounds.

All other carbocyclic compounds belong to the alicyclic series.

Both acyclic (aliphatic) and cyclic hydrocarbons can contain multiple (double or triple) bonds. Such hydrocarbons are called unlimited(unsaturated) in contrast to limiting (saturated), containing only single bonds.

Saturated aliphatic hydrocarbons are called alkanes, they have the general formula C n H 2n+2, where n is the number of carbon atoms. Their old name is often used today - paraffins:

Unsaturated aliphatic hydrocarbons containing one double bond are called alkenes. They have the general formula C n H 2n:

Unsaturated aliphatic hydrocarbons with two double bonds are called alkadienes. Their general formula is C n H 2n-2:

Unsaturated aliphatic hydrocarbons with one triple bond are called alkynes. Their general formula is C n H 2n - 2:

Saturated alicyclic hydrocarbons - cycloalkanes, their general formula is C n H 2n:

A special group of hydrocarbons, aromatic, or arenas(with a closed common n-electronic system), known from the example of hydrocarbons with the general formula C n H 2n - 6:

Thus, if their molecules contain one or larger number hydrogen atoms are replaced by other atoms or groups of atoms (halogens, hydroxyl groups, amino groups, etc.), hydrocarbon derivatives are formed: halogen derivatives, oxygen-containing, nitrogen-containing and other organic compounds.

Homologous series of hydrocarbons

Hydrocarbons and their derivatives with the same functional group form homologous series.

Homologous series name a series of compounds belonging to the same class (homologues), arranged in increasing order of their relative molecular masses, similar in structure and chemical properties, where each member differs from the previous one by the homologous difference CH 2. For example: CH 4 - methane, C 2 H 6 - ethane, C 3 H 8 - propane, C 4 H 10 - butane, etc. The similarity of the chemical properties of homologues greatly simplifies the study of organic compounds.

Hydrocarbon isomers

Those atoms or groups of atoms that determine the most characteristic properties of this class of substances are called functional groups.

Halogen derivatives of hydrocarbons can be considered as products of the replacement of one or more hydrogen atoms in hydrocarbons with halogen atoms. In accordance with this, there can be finite and unsaturated mono-, di-, tri- (in the general case poly-) halogen derivatives.

General formula of monohalogen derivatives of saturated hydrocarbons:

and the composition is expressed by the formula

where R is the remainder of a saturated hydrocarbon (alkane), a hydrocarbon radical (this designation is used further when considering other classes of organic substances), G is a halogen atom (F, Cl, Br, I).

For example:

Here is one example of a dihalogen derivative:

TO oxygen-containing organic substances include alcohols, phenols, aldehydes, ketones, carboxylic acids, ethers and esters. Alcohols are derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by hydroxyl groups.

Alcohols are called monohydric if they have one hydroxyl group, and saturated if they are derivatives of alkanes.

General formula for limit monohydric alcohols:

and their composition is expressed by the general formula:

For example:

Known examples polyhydric alcohols, i.e. having several hydroxyl groups:

Phenols- derivatives of aromatic hydrocarbons (benzene series), in which one or more hydrogen atoms in the benzene ring are replaced by hydroxyl groups.

The simplest representative with the formula C 6 H 5 OH or

called phenol.

Aldehydes and ketones- derivatives of hydrocarbons containing carbonyl group of atoms

(carbonyl).

In molecules aldehydes one carbonyl bond goes to combine with a hydrogen atom, the other - with a hydrocarbon radical. General formula of aldehydes:

For example:

In case ketones the carbonyl group is connected to two (generally different) radicals, the general formula of ketones is:

For example:

The composition of saturated aldehydes and ketones is expressed by the formula C 2n H 2n O.

Carboxylic acids- hydrocarbon derivatives containing carboxyl groups

(or -COOH).

If there is one carboxyl group in an acid molecule, then the carboxylic acid is monobasic. General formula of saturated monobasic acids:

Their composition is expressed by the formula C n H 2n O 2.

For example:

Ethers are organic substances containing two hydrocarbon radicals connected by an oxygen atom: R-O-R or R 1 -O-R 2.

Radicals can be the same or different. The composition of ethers is expressed by the formula C n H 2n+2 O.

For example:

Esters - compounds formed by replacing the hydrogen atom of the carboxyl group in carboxylic acids with a hydrocarbon radical.

General formula of esters:

For example:

Nitro compounds- derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by a nitro group -NO 2.

General formula of saturated mononitro compounds:

and the composition is expressed by the general formula C n H 2n+1 NO 2 .

For example:

Nitro derivatives of arenes:

Amines- compounds that are considered to be derivatives of ammonia (NH 3), in which the hydrogen atoms are replaced by hydrocarbon radicals. Depending on the nature of the radical, amines can be aliphatic, for example:

and aromatic, for example:

Depending on the number of hydrogen atoms replaced by radicals, the following are distinguished:

primary amines with the general formula:

secondary- with the general formula:

tertiary- with the general formula:

In a particular case, secondary and tertiary amines may have the same radicals.

Primary amines can also be considered as derivatives of hydrocarbons (alkanes), in which one hydrogen atom is replaced by an amino group -NH 2. The composition of saturated primary amines is expressed by the formula C n H 2n + 3 N.

For example:

Amino acids contain two functional groups connected to a hydrocarbon radical: amino group -NH 2 and carboxyl -COOH.

The general formula of α-amino acids (they are most important for the construction of proteins that make up living organisms):

The composition of saturated amino acids containing one amino group and one carboxyl is expressed by the formula C n H 2n + 1 NO 2.

For example:

Other important organic compounds are known that have several different or identical functional groups, long linear chains connected to benzene rings. In such cases, a strict determination of whether a substance belongs to a specific class is impossible. These compounds are often classified into specific groups of substances: carbohydrates, proteins, nucleic acids, antibiotics, alkaloids, etc.

Currently, many compounds are also known that can be classified as both organic and inorganic. x are called organoelement compounds. Some of them can be considered as hydrocarbon derivatives.

For example:

There are compounds that have the same molecular formula, expressing the composition of the substances.

The phenomenon of isomerism is that there can be several substances with different properties, having the same molecular composition, but different structures. These substances are called isomers.

In our case, these are interclass isomers: cycloalkanes and alkanes, alkadienes and alkynes, saturated monohydric alcohols and ethers, aldehydes and ketones, saturated monocarboxylic acids and esters.

Structural isomerism

The following varieties are distinguished structural isomerism: isomerism of the carbon skeleton, positional isomerism, isomerism of various classes of organic compounds (interclass isomerism).

Isomerism of the carbon skeleton is due to different bond order between carbon atoms, forming the skeleton of the molecule. As has already been shown, the molecular formula C 4 H 10 corresponds to two hydrocarbons: n-butane and isobutane. For the hydrocarbon C5H12, three isomers are possible: pentane, isopentane and neopentane.

As the number of carbon atoms in a molecule increases, the number of isomers increases rapidly. For hydrocarbon C 10 H 22 there are already 75 of them, and for hydrocarbon C 20 H 44 - 366,319.

Positional isomerism is due to different positions of the multiple bond, substituent, and functional group with the same carbon skeleton of the molecule:

Isomerism of different classes of organic compounds (interclass isomerism) is due to different positions and combinations of atoms in the molecules of substances that have the same molecular formula, but belong to different classes. Thus, the molecular formula C 6 H 12 corresponds to the unsaturated hydrocarbon hexene-1 and the cyclic hydrocarbon cyclohexane.

The isomers are a hydrocarbon related to alkynes - butine-1 and a hydrocarbon with two double bonds in the butadiene-1,3 chain:

Diethyl ether and butyl alcohol have the same molecular formula C 4 H 10 O:

The structural isomers are aminoacetic acid and nitroethane, corresponding to the molecular formula C 2 H 5 NO 2:

Isomers of this type contain different functional groups and belong to different classes of substances. Therefore, they differ in physical and chemical properties much more than carbon skeleton isomers or positional isomers.

Spatial isomerism

Spatial isomerism is divided into two types: geometric and optical.

Geometric isomerism is characteristic of compounds containing double bonds, and cyclic compounds. Since free rotation of atoms around a double bond or in a ring is impossible, the substituents can be located either on the same side of the plane of the double bond or ring (cis position) or on opposite sides (trans position). The designations cis and trans usually refer to a pair of identical substituents.

Geometric isomers differ in physical and chemical properties.

Optical isomerism occurs if the molecule is incompatible with its image in the mirror. This is possible when the carbon atom in the molecule has four different substituents. This atom is called asymmetric. An example of such a molecule is the α-aminopropionic acid (α-alanine) molecule CH 3 CH(NH 2)OH.

The α-alanine molecule cannot coincide with its mirror image during any movement. Such spatial isomers are called mirror, optical antipodes, or enantiomers. All physical and almost all chemical properties of such isomers are identical.

The study of optical isomerism is necessary when considering many reactions occurring in the body. Most of these reactions occur under the action of enzymes - biological catalysts. The molecules of these substances must fit the molecules of the compounds on which they act, like a key to a lock; therefore, the spatial structure, the relative arrangement of sections of the molecules and other spatial factors are of great importance for the course of these reactions. Such reactions are called stereoselective.

Most natural compounds are individual enantiomers, and their biological effects (ranging from taste and smell to medicinal effect) differs sharply from the properties of their optical antipodes obtained in the laboratory. Such a difference in biological activity is of great importance, since it underlies the most important property of all living organisms - metabolism.

Isomerism

Electronic structure of the carbon atom

Carbon, which is part of organic compounds, exhibits a constant valence. The last energy level of the carbon atom contains 4 electrons, two of which occupy a 2s orbital having spherical shape, and two electrons occupy 2p orbitals, which have a dumbbell-like shape. When excited, one electron from the 2s orbital can move to one of the vacant 2p orbitals. This transition requires some energy expenditure (403 kJ/mol). As a result, the excited carbon atom has 4 unpaired electrons and its electronic configuration is expressed by the formula 2s 1 2p 3 .. Thus, in the case of the methane hydrocarbon (CH 4), the carbon atom forms 4 bonds with the s-electrons of hydrogen atoms. In this case, 1 connection should be formed type s-s(between the s-electron of a carbon atom and the s-electron of a hydrogen atom) and 3 p-s bonds (between 3 p-electrons of a carbon atom and 3 s-electrons of 3 hydrogen atoms). This leads to the conclusion that the four covalent bonds formed by the carbon atom are unequal. However, practical experience in chemistry indicates that all 4 bonds in a methane molecule are absolutely equivalent, and the methane molecule has a tetrahedral structure with bond angles of 109.5 0, which could not be the case if the bonds were unequal. After all, only the orbitals of p-electrons are oriented in space along the mutually perpendicular axes x, y, z, and the orbital of the s-electron has a spherical shape, so the direction of formation of a bond with this electron would be arbitrary. The theory of hybridization was able to explain this contradiction. L. Polling suggested that in any molecules there are no bonds isolated from each other. When bonds are formed, the orbitals of all valence electrons overlap. Several types are known hybridization of electron orbitals. It is assumed that in the molecule of methane and other alkanes, 4 electrons enter into hybridization.

Hybridization of carbon atom orbitals

Orbital hybridization is a change in the shape and energy of some electrons during the formation of a covalent bond, leading to more efficient orbital overlap and increased bond strength. Hybridization of orbitals always occurs when electrons belonging to various types orbitals.

1. sp 3 -hybridization(first valence state of carbon). During sp 3 hybridization, 3 p orbitals and one s orbital of an excited carbon atom interact in such a way that the resulting orbitals are absolutely identical in energy and symmetrically located in space. This transformation can be written like this:

During hybridization, the total number of orbitals does not change, but only their energy and shape change. It is shown that sp 3 -hybridization orbitals resemble a three-dimensional figure eight, one of the blades of which is much larger than the other. Four hybrid orbitals are extended from the center to the vertices of a regular tetrahedron at angles of 109.5 0. Bonds formed by hybrid electrons (for example, an s-sp 3 bond) are stronger than bonds formed by unhybridized p electrons (for example, an s-p bond). Because the hybrid sp 3 orbital provides a larger area of electron orbital overlap than the non-hybridized p orbital. Molecules in which sp 3 hybridization occurs have a tetrahedral structure. These, in addition to methane, include methane homologues, inorganic molecules such as ammonia. The figures show a hybridized orbital and a tetrahedral methane molecule.

The chemical bonds that arise in methane between carbon and hydrogen atoms are of the type σ-bonds (sp 3 -s-bond). Generally speaking, any sigma bond is characterized by the fact that the electron density of two interconnected atoms overlaps along the line connecting the centers (nuclei) of the atoms. σ-Bonds correspond to the maximum possible degree of overlap of atomic orbitals, so they are quite strong.

2. sp 2 -hybridization(second valence state of carbon). It arises as a result of the overlap of one 2s and two 2p orbitals. The resulting sp 2 -hybrid orbitals are located in the same plane at an angle of 120 0 to each other, and the non-hybridized p-orbital is perpendicular to it. The total number of orbitals does not change - there are four of them.

The sp 2 hybridization state occurs in alkene molecules, in carbonyl and carboxyl groups, i.e. in compounds containing a double bond. Thus, in the ethylene molecule, the hybridized electrons of the carbon atom form 3 σ bonds (two sp 2 -s type bonds between the carbon atom and hydrogen atoms and one sp 2 -sp 2 type bond between the carbon atoms). The remaining unhybridized p-electron of one carbon atom forms a π-bond with the unhybridized p-electron of the second carbon atom. A characteristic feature of the π bond is that the overlap of electron orbitals occurs outside the line connecting the two atoms. The overlap of orbitals occurs above and below the σ bond connecting both carbon atoms. Thus, a double bond is a combination of σ and π bonds. The first two figures show that in the ethylene molecule the bond angles between the atoms forming the ethylene molecule are 120 0 (corresponding to the spatial orientation of the three sp 2 hybrid orbitals). The figures show the formation of a π bond.

Since the overlap area of unhybridized p-orbitals in π bonds is smaller than the overlap area of orbitals in σ bonds, the π bond is less strong than the σ bond and is more easily broken in chemical reactions.

3. sp hybridization(third valence state of carbon). In the state of sp-hybridization, the carbon atom has two sp-hybrid orbitals located linearly at an angle of 180 0 to each other and two non-hybridized p-orbitals located in two mutually perpendicular planes. sp-hybridization is characteristic of alkynes and nitriles, i.e. for compounds containing a triple bond.

Thus, in an acetylene molecule, the bond angles between atoms are 180 o. The hybridized electrons of a carbon atom form 2 σ bonds (one sp-s bond between a carbon atom and a hydrogen atom and another sp-sp bond between carbon atoms. Two unhybridized p electrons of one carbon atom form two π bonds with unhybridized p electrons of the second carbon atom. The overlap of p-electron orbitals occurs not only above and below the σ bond, but also in front and behind, and the total cloud of p-electrons has a cylindrical shape. Thus, the triple bond is a combination of one σ bond and two π bonds. The presence in the acetylene molecule of less strong two π-bonds ensures the ability of this substance to enter into addition reactions with the cleavage of the triple bond.

Reference material for taking the test:

Periodic table

Solubility table

1. Electronic structure of the carbon atom;

2. Hybridization of atomic orbitals;

3. The nature of the chemical bond;

4. Types of chemical bonds.

When a chemical bond is formed, energy is released, so the appearance of two new valence possibilities leads to the release of additional energy (1053.4 kJ/mol), which exceeds the energy expended on the pairing of 2s electrons (401 kJ/mol).

Orbitals of different shapes (s, p) mix when forming a bond, giving new equivalent hybridized orbitals (hybridization theory, L. Pauling, D. Slater, 1928-1931). The concept of hybridization applies only to molecules, not to atoms, and only orbitals enter into hybridization, not the electrons on them.

Unlike the unhybridized s- and p-orbitals, the hybrid orbital is polar (the electron density is shifted) and is capable of forming stronger bonds.

Valence states of the carbon atom

Shaft. comp.	Interacting orbitals	Space page	Communication type	Shaft. corner
		tetrahedral

		linear

As the type of hybridization of a carbon atom changes, its properties also change. When going from sp 3 to sp-, the fraction of the s-orbital in the composition of the hybridized cloud increases, which entails a change in its shape. The boundaries of the electron cloud approach the nucleus in the case of sp 2 and sp orbitals, compared to the sp 3 cloud. This is reflected in the increase in electronegativity of the carbon atom in the series: sp 3< sp 2 < sp. В связи с этим, уменьшается ковалентный радиус, увеличивается полярность связи.

Types of chemical bond

Ionic bond

Occurs in the case of complete donation of electrons by some atoms and acquisition of them by others. In this case, atoms turn into ions.

Covalent bond

Formed by sharing electrons. The bonding of atoms in a molecule is carried out by an electron pair belonging simultaneously to two atoms. The sharing of electrons is possible in two ways:

1) colligation (exchange mechanism);

2) coordination (donor-acceptor mechanism).

There are two types of covalent bonds: σ (sigma)- and π (pi)-bonds.

A σ bond is a single covalent bond formed when atomic orbitals overlap along a straight line (axis) connecting the nuclei of two bonded atoms with a maximum overlap on this straight line.

A π bond is a bond formed by the lateral overlap of unhybridized p z-atomic orbitals with a maximum overlap on both sides of the straight line connecting the nuclei of atoms.

Quantitative characteristics of covalent bonds

1. Bond energy is the energy released when a bond is formed or required to break it.

2. Bond length is the distance between the centers of bonded atoms.

3. Bond polarity – uneven distribution of electron density.

4. Bond polarizability – displacement of bond electrons under the influence of an external electric field, including that of another reacting particle.

Intermolecular interactions

Task No. 1

Explanation:

1) Dehydrohalogenation of chlorobutane under the action of an alcoholic alkali solution:

2) Oxidation of the double bond of butene-1 with an acidified solution of potassium permanganate (cleavage of the double bond):

3) Esterification reaction - the formation of an ester from an alcohol and a carboxylic acid:

4) Alkaline hydrolysis of isopropylpropionate to form sodium propionate and isopropyl alcohol:

5) Fusion of propionic acid salt with alkali to form ethane and sodium carbonate:

Task No. 2

Write the reaction equations that can be used to carry out the following transformations:

Explanation:

1) Methane is obtained from sodium acetate by a decarboxylation reaction, which occurs when it is fused with an alkali, for example, sodium hydroxide:

2) When methane interacts with chlorine in a one to one molar ratio, monochloromethane (X 1) and hydrogen chloride are formed predominantly:

3) When treating monochloromethane with an aqueous solution of alkali, nucleophilic substitution of the chlorine atom with a hydroxyl group occurs to form methyl alcohol (X 2):

4) Methanal (formaldehyde) can be obtained from methyl alcohol by acting as a weak oxidizing agent - copper (II) oxide when heated:

5) Potassium permanganate, acidified with sulfuric acid, oxidizes methanal to carbon dioxide and water. In this case, since the solution environment is acidic, the permanganate ion is reduced to divalent manganese:

Task No. 3

Write the reaction equations that can be used to carry out the following transformations:

When writing reaction equations, use the structural formulas of organic substances.

Explanation:

1) When propanol-1 is exposed to hydrogen bromide, a reaction occurs in which the hydroxyl group in alcohol is replaced by a bromine atom to form 1-bromopropane (X 1)

2) Propene can be obtained from 1-bromopropane by dehydrobromination reaction with an alcoholic alkali solution, for example, sodium hydroxide:

3) In an acidic environment, propene can react with water in accordance with Markovnikov’s rule - hydrogen goes to the most hydrogenated atom, and the hydroxyl group to the least hydrogenated one. This produces isopropyl alcohol:

4) Isopropyl alcohol(X 2) when oxidized by potassium permanganate in an aqueous solution, it turns into acetone, and since the solution medium is neutral, the permanganate ion is reduced from the oxidation state +7 to the oxidation state +4 - manganese dioxide is formed:

5) Acetone can be converted to isopropanol (X 2) by hydrogenation reaction when heated, using a hydrogenation catalyst, for example, nickel:

Task No. 4

Write the reaction equations that can be used to carry out the following transformations:

When writing reaction equations, use the structural formulas of organic substances.

1) When a carboxylic acid salt is calcined with an excess of alkali, a hydrocarbon is formed, in this specific case– benzene (X 1):

2) Benzene undergoes an alkylation reaction with propene in the presence of acid catalysts, resulting in the formation of cumene (X 2):

3) Cumene reacts with chlorine in the light according to a chain radical mechanism. With a lack of chlorine, the replacement of the hydrogen atom at the tertiary carbon atom mainly occurs:

4) When a chlorine derivative is exposed to an alcoholic solution of alkali, hydrogen chloride is eliminated:

5) In the last reaction, at first glance, you might think that a hydrocarbon with a double bond is converted into the corresponding diol, but in order to form glycol, cooling (0-10 o C) is needed, not heating. When heated, deep oxidation to potassium benzoate and potassium carbonate will occur.

The problem is that, apparently, in this assignment from the FIPI bank, which, by the way, some people came across during the early Unified State Examination in April 2016, there was a typo, and they meant 0 o C, not heating.

Task No. 5

Write the reaction equations that can be used to carry out the following transformations:

When writing reaction equations, use the structural formulas of organic substances.

1) When acting on bromoethane aqueous solution alkali, a nucleophilic substitution of the bromine atom with a hydroxide ion occurs, resulting in the formation of ethyl alcohol (X 1):

2) Ethyl alcohol (X 1) can be converted into acetic acid by oxidizing it with an aqueous solution of potassium permanganate in an acidic medium when heated:

3) Acetic acid reacts with neutralization with alkalis, for example, with sodium hydroxide, resulting in the formation of sodium acetate (X 2):

4) After evaporating an aqueous solution of sodium acetate (X 2) and fusing the resulting solid sodium acetate with solid sodium hydroxide, a decarboxylation reaction occurs to form methane (X 3) and sodium carbonate:

5) Pyrolysis of methane at 1500 o C leads to the formation of acetylene (X 4) and hydrogen:

Task No. 6

Write the reaction equations that can be used to carry out the following transformations:

When writing reaction equations, use the structural formulas of organic substances.

1) Propyl acetate, being an ester, undergoes alkaline hydrolysis to form potassium acetate (X 1) and propanol:

2) Methane is obtained from potassium acetate through the decarboxylation reaction that occurs when it is fused with alkali:

3) At a temperature of 1200 o C and rapid cooling (to prevent the decomposition of acetylene into simple substances), methane decomposes into acetylene (X 2) and hydrogen:

4) Dimerization of acetylene occurs in the presence of catalysts - a hydrochloric acid solution of copper (I) and ammonium chlorides - with the formation of vinyl acetylene:

5) When vinyl acetylene is passed through bromine water, discoloration is observed bromine water due to the addition of bromine to multiple bonds with the formation of a saturated bromo derivative of butane - 1,1,2,2,3,4-hexabromobutane (X 3):

Task No. 7

Write the reaction equations that can be used to carry out the following transformations:

When writing reaction equations, use the structural formulas of organic substances.

1) In industry, formaldehyde is produced by the oxidation of methane on an aluminum phosphate catalyst at a temperature of 450 o C and a pressure of 1-2 MPa:

2) During hydrogenation on catalysts (Pt, Pd, Ni), the carbonyl group of formaldehyde is reduced to hydroxyl, i.e. aldehyde turns into alcohol - methanol (X 1):

3) Metallic sodium reacts with methanol to form sodium methoxide (X 2) and release hydrogen:

4) Reacting with hydrochloric acid, sodium methoxide is converted back into methanol (X 1):

5) Potassium permanganate in an acidic environment when heated oxidizes methyl alcohol to carbon dioxide (X 3) (Mn +7 → Mn +2; C -2 → C +4):

Task No. 8

Write the reaction equations that can be used to carry out the following transformations:

1) In the presence of aluminum oxide at a temperature of 400 o C, alcohol dehydrates to form ethylene (X 1) and water:

2) Potassium permanganate in neutral environment oxidizes ethylene to ethylene glycol (X 2) (Mn +7 → Mn +4; 2C -2 → 2C -1):

3) When excess hydrogen bromide acts on ethylene glycol, hydroxyl groups are replaced by bromine anions, resulting in the formation of 1,2-dibromoethane (X 3):

4) Ethine (or acetylene) can be obtained by treating 1,2-dibromoethane with an alcoholic alkali solution:

5) According to the reaction of M.G. Kucherov, in the presence of mercury salts in an acidic environment (in an aqueous or alcohol solution), acetylene is converted into ethanal:

Task No. 9

Write the reaction equations that can be used to carry out the following transformations:

1) Acetone (propanone) can be obtained by the reaction of M.G. Kucherov, acting on propyne (X 1) with water in the presence of mercury salts in an acidic medium (in an aqueous or alcoholic solution):

2) During hydrogenation on catalysts (Pt, Pd, Ni), the carbonyl group of the ketone is reduced to hydroxyl, i.e. the ketone is converted into a secondary alcohol - isopropanol (X 2):

3) When hydrogen bromide acts on isopropanol, a nucleophilic substitution of the hydroxyl group with bromine anion occurs, resulting in the formation of 2-bromopropane:

4) Under the action of an alcohol solution of alkali, 2-bromopropane is converted into an unsaturated hydrocarbon - propylene (X 3):

5) By dehydrogenation of propylene on a catalyst (Pt, Pd, Ni), propyne (X 1) can be obtained:

Task No. 10

Write the reaction equations that can be used to carry out the following transformations:

1) Bromomethane can be obtained by the action of bromine on methane (X 1) in the light. The substitution reaction occurs via a free radical mechanism:

2) When bromomethane reacts with ammonia, an amine salt is first formed, which, with an excess of ammonia, turns into free amine. In the case of methylamine, methylamine (X 2) and ammonium bromide are formed:

3) Nitrous acid is unstable, so it is obtained during the reaction by acting on an acidified amine solution with sodium nitrite. In the case of the primary amine - methylamine - the release of nitrogen is observed, and methanol is formed in the solution (X 3):

4) By treating methyl alcohol with copper (II) oxide upon heating, we obtain formaldehyde, while Cu +2 is reduced to Cu 0:

5) When formaldehyde is oxidized with potassium permanganate in an acidic environment, carbon dioxide (X 4) is released (Mn +7 → Mn +2; C 0 → C +4):

Task No. 11

Write the reaction equations that can be used to carry out the following transformations:

1) Alkanes with a main chain of 6 or more carbon atoms are capable of undergoing a dehydrocyclization reaction, in which the resulting six-membered ring is further dehydrogenated and converted into the energetically more stable benzene ring of an aromatic hydrocarbon. In this case, the resulting cyclohexane is dehydrogenated into benzene (X 1):

2) Alkylation of aromatic hydrocarbons with alkyl halides and in the presence of anhydrous AlCl 3 is a classic example of the Friedel-Crafts reaction. The reaction is an electrophilic substitution on the benzene ring. Alkylation of benzene with methyl chloride leads to the formation of toluene (X 2):

3) When toluene is exposed to excess chlorine in the light, all hydrogen atoms in the methyl radical of toluene are replaced by chlorine. The substitution reaction occurs via a free radical mechanism:

4) During the alkaline hydrolysis of trihalides with chlorine atoms at one carbon atom, salts of carboxylic acids are formed in high yields (in this case, potassium benzoate (X 3)):

5) From potassium benzoate, benzene (X 1) is obtained through the decarboxylation reaction that occurs when it is fused with alkali:

Task No. 12

Write the reaction equations that can be used to carry out the following transformations:

1) 1,2-dichloroethane is a geminal dichloro derivative of ethane. Under conditions of an aqueous solution of alkali, 1,2-dichloroethane is converted into a carbonyl compound - acetaldehyde:

2) When carbonyl compounds are reduced with hydrogen, alcohols are formed. Thus, by passing a mixture of acetaldehyde and hydrogen vapor over a nickel catalyst, ethanol can be obtained (X 1):

3) The replacement of the hydroxyl group of alcohol with an amino group occurs under harsh conditions. By passing ethanol vapor and ammonia over heated aluminum oxide, ethylamine is obtained:

4) When carbon dioxide is passed through an aqueous solution of ethylamine, ethylammonium bicarbonate (X 2) is formed:

5) When heated, ethylammonium bicarbonate decomposes into carbon dioxide, ethylamine (X 3) and water:

Task No. 13

Write the reaction equations that can be used to carry out the following transformations:

1) Acetylene (ethyne) undergoes a hydration reaction in the presence of mercury salts in an aqueous solution to form acetaldehyde (Kucherov reaction) (X 1):

2) Acetaldehyde, when exposed to an acidified aqueous solution of potassium permanganate, is converted into acetic acid:

3) Acetic acid reacts with neutralization with sodium hydroxide, resulting in the formation of sodium acetate (X 2) and water:

4) Sodium acetate reacts with haloalkanes to form esters, in this case methyl ester of acetic acid (methyl acetate) is formed (X 3):

5) Esters in the presence of acids can undergo hydrolysis reactions. When methyl acetate is hydrolyzed in an acidic environment, acetic acid and methanol are formed:

Task No. 14

Write the reaction equations that can be used to carry out the following transformations:

1) When an alcoholic alkali solution acts on any of the dibromoethane isomers, acetylene is formed (X 1):

2) Acting on acetylene (X 1) with water in the presence of mercury salts in an acidic medium (in an aqueous or alcohol solution), acetaldehyde (X 2) is obtained (reaction of M.G. Kucherov):

3) When acetaldehyde is oxidized with potassium permanganate in an acidic environment, acetic acid is formed (Mn +7 → Mn +2; C +1 → C +3):

4) Chloroacetic acid can be obtained by the action of chlorine on acetic acid in the light. The substitution reaction proceeds by a free radical mechanism, as a result of which the hydrogen atom of the alkyl radical is replaced by chlorine (X 3):

5) When chloroacetic acid is treated with ammonia, the amino acid glycine is formed:

Task No. 15

Write the reaction equations that can be used to carry out the following transformations:

1) At temperatures above 140 0 C in the presence of concentrated sulfuric acid, alcohols undergo intramolecular dehydration with the formation of alkene and water. In this case, at 180 0 C and the action of conc. H 2 SO 4 propanol-1 is converted into propylene (X 1):

2) When propylene is passed through bromine water, bromine water becomes discolored due to the addition of bromine to the double bond to form 1,2-dibromopropane (X 2):

3) When an alcohol solution of alkali reacts with 1,2-dibromopropane, propyne is formed:

4) By treating propyne with water in the presence of mercury salts in an acidic medium (in an aqueous or alcohol solution), acetone (X 3) is obtained (reaction of M.G. Kucherov):

5) By passing a mixture of acetone and hydrogen vapor over a palladium catalyst, 2-propanol (or isopropanol) is obtained (X 4):

Task No. 16

Write the reaction equations that can be used to carry out the following transformations:

1) Cyclopropane adds hydrogen bromide with ring opening, resulting in the formation of 1-bromopropane:

2) In laboratory conditions, alkanes are obtained by the Wurtz reaction from haloalkanes. Partial positive charge on the carbon atom at the halogen in halogen derivatives makes it possible for these compounds to react with active metals. Monohalogenalkanes already at room temperature react with sodium, turning into alkanes with a double carbon skeleton. Thus, from two molecules of 1-bromopropane, n-hexane (X 1) is obtained:

3) Alkanes having six or more carbon atoms in a molecule can enter into more complex reactions dehydrogenation, during which the elimination of hydrogen is accompanied by the closure of the chain into a cycle: dehydrogenation - cyclization reactions. In this case, hexane is converted to benzene (X 2):

4) Toluene is obtained by alkylation of benzene with methyl halide in the presence of an AlCl 3 catalyst (electrophilic substitution, S E mechanism):

5) Methyl group toluene is oxidized by potassium permanganate in an acidic environment to a carboxyl group, therefore, toluene is converted into benzoic acid (X 3) (Mn +7 → Mn +2; C -3 → C +3):

Task No. 17

Write the reaction equations that can be used to carry out the following transformations:

1) In laboratory conditions, propane can be obtained by the Wurtz reaction from haloalkanes - chloroethane and chloromethane, but this reaction is associated with the formation of two by-products - butane and ethane. Monohalogenalkanes at room temperature are able to react with sodium:

2) By dehydrogenating propane on a catalyst (Pt, Pd, Ni), propylene can be obtained (X 1):

3) When an alkene is oxidized with permanganate in a neutral environment in the cold, a dihydric alcohol, an alkali and manganese (IV) oxide are formed. In this case, propanediol-1,2 (X 2) is formed from propylene (Mn +7 → Mn +4; C -2 → C -1, C -1 → C 0):

4) Polyhydric alcohols capable of undergoing nucleophilic substitution reactions with hydrogen halides. Acting with an excess of hydrogen bromide on propanediol-1,2, 1,2-dibromopropane (X 3) is obtained:

5) When an alcohol solution of alkali acts on a dihaloalkane - 1,2-dibromopropane - propine (X 4) is formed.

Types of bonds in organic chemistry. Electronic structure of organic compounds How to count bonds in organic chemistry

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