Butlerov Alexander Mikhailovich. Development of the theory of the chemical structure of organic compounds
Man has long learned to use various substances to prepare food, dyes, clothing, and medicines. Over time, it has accumulated sufficient quantity information about the properties of certain substances, which made it possible to improve methods of their production, processing, etc. And it turned out that many mineral (inorganic substances) can be obtained directly.
But some substances used by man were not synthesized by him, because they were obtained from living organisms or plants. These substances were called organic. Organic substances could not be synthesized in the laboratory. At the beginning of the 19th century, such a doctrine as vitalism (vita - life) actively developed, according to which organic substances arise only thanks to “ vitality“and it is impossible to create them “artificially.”
But as time passed and science developed, new facts appeared about organic substances that ran counter to the existing vitalist theory.
In 1824, the German scientist F. Wöhler synthesized oxalic acid for the first time in the history of chemical science – organic matter from inorganic substances (cyanogen and water):
(CN) 2 + 4H 2 O → COOH - COOH + 2NH 3
In 1828, Wöller heated sodium cyanate with ammonium sulfur and synthesized urea - waste product of animal organisms:
NaOCN + (NH 4) 2 SO 4 → NH 4 OCN → NH 2 OCNH 2
These discoveries played an important role in the development of science in general, and chemistry in particular. Chemical scientists began to gradually move away from vitalistic teaching, and the principle of dividing substances into organic and inorganic revealed its inconsistency.
Currently substances still divided into organic and inorganic, but the separation criterion is slightly different.
Substances are called organic containing carbon, they are also called carbon compounds. There are about 3 million such compounds, the remaining compounds are about 300 thousand.
Substances that do not contain carbon are called inorganic And. But there are exceptions to general classification: There are a number of compounds that contain carbon, but they belong to inorganic substances (carbon monoxide and dioxide, carbon disulfide, carbonic acid and its salts). All of them are similar in composition and properties to inorganic compounds.
In the course of studying organic substances, new difficulties have arisen: based on theories about inorganic substances, it is impossible to reveal the laws of the structure of organic compounds and explain the valence of carbon. Carbon in different compounds had different valences.
In 1861, the Russian scientist A.M. Butlerov was the first to synthesize a sugary substance.
When studying hydrocarbons, A.M. Butlerov realized that they represent a completely special class chemical substances. Analyzing their structure and properties, the scientist identified several patterns. They formed the basis of the theories chemical structure.
1. The molecule of any organic substance is not random; the atoms in the molecules are connected to each other in a certain sequence according to their valencies. Carbon in organic compounds is always tetravalent.
2. The sequence of interatomic bonds in a molecule is called its chemical structure and is reflected by one structural formula (structural formula).
3. Chemical structure can be determined chemical methods. (Modern physical methods are also currently used).
4. The properties of substances depend not only on the composition of the molecules of the substance, but on their chemical structure (the sequence of combination of atoms of elements).
5. By the properties of a given substance one can determine the structure of its molecule, and by the structure of the molecule – anticipate properties.
6. Atoms and groups of atoms in a molecule exert mutual influence on each other.
This theory became the scientific foundation of organic chemistry and accelerated its development. Based on the provisions of the theory, A.M. Butlerov described and explained the phenomenon isomerism, predicted the existence of various isomers and obtained some of them for the first time.
Consider the chemical structure of ethane – C2H6. Having designated the valence of elements with dashes, we will depict the ethane molecule in the order of connection of atoms, that is, we will write the structural formula. According to the theory of A.M. Butlerov, it will have the following form:
Hydrogen and carbon atoms are bound into one particle, the valence of hydrogen is equal to one, and that of carbon – four. Two carbon atoms connected by a carbon bond – carbon (C – WITH). Ability of carbon to form C – The C-bond is understandable based on the chemical properties of carbon. The carbon atom has four electrons on its outer electron layer; the ability to give up electrons is the same as the ability to gain missing ones. Therefore, carbon most often forms compounds with covalent bond, that is, due to the formation of electron pairs with other atoms, including carbon atoms with each other.
This is one of the reasons for the diversity of organic compounds.
Compounds that have the same composition but different structure, are called isomers. The phenomenon of isomerism – one of the reasons for the diversity of organic compounds
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The largest event in the development of organic chemistry was the creation in 1961 by the great Russian scientist A.M. Butlerov theories of the chemical structure of organic compounds.
Before A.M. Butlerov considered it impossible to know the structure of a molecule, that is, the order of chemical bonds between atoms. Many scientists even denied the reality of atoms and molecules.
A.M. Butlerov denied this opinion. He came from the right place materialistic and philosophical ideas about the reality of the existence of atoms and molecules, about the possibility of knowing the chemical bond of atoms in a molecule. He showed that the structure of a molecule can be established experimentally by studying the chemical transformations of a substance. Conversely, knowing the structure of the molecule, one can deduce the chemical properties of the compound.
The theory of chemical structure explains the diversity of organic compounds. It is due to the ability of tetravalent carbon to form carbon chains and rings, combine with atoms of other elements and the presence of isomerism in the chemical structure of organic compounds. This theory laid the scientific foundations of organic chemistry and explained its most important laws. The basic principles of his theory A.M. Butlerov outlined it in his report “On the theory of chemical structure.”
The main principles of the theory of structure are as follows:
1) in molecules, atoms are connected to each other in a certain sequence in accordance with their valence. The order in which the atoms bond is called chemical structure;
2) the properties of a substance depend not only on which atoms and in what quantity are included in its molecule, but also on the order in which they are connected to each other, i.e., on the chemical structure of the molecule;
3) atoms or groups of atoms that form a molecule mutually influence each other.
In the theory of chemical structure, much attention is paid to the mutual influence of atoms and groups of atoms in a molecule.
Chemical formulas, which depict the order of connection of atoms in molecules, are called structural formulas or formulas of structure.
The importance of the theory of chemical structure of A.M. Butlerova:
1) is the most important part of the theoretical foundation of organic chemistry;
2) in importance it can be compared with the Periodic Table of Elements by D.I. Mendeleev;
3) it made it possible to systematize a huge practical material;
4) made it possible to predict in advance the existence of new substances, as well as indicate ways to obtain them.
The theory of chemical structure serves as the guiding basis for all research in organic chemistry.
12 Phenols, hydroxy derivatives aromatic compounds, containing one or more hydroxyl groups (–OH) bonded to the carbon atoms of the aromatic nucleus. Based on the number of OH groups, monoatomic compounds are distinguished, for example, oxybenzene C 6 H 5 OH, usually called simply phenol, hydroxytoluenes CH 3 C 6 H 4 OH - the so-called cresols, oxynaphthalenes – naphthols, diatomic, for example dioxybenzenes C 6 H 4 (OH) 2 ( hydroquinone, pyrocatechin, resorcinol), polyatomic, for example pyrogallol, phloroglucinol. F. - colorless crystals with a characteristic odor, less often liquids; highly soluble in organic solvents (alcohol, ether, oensol). Possessing acidic properties, phosphorus forms salt-like products - phenolates: ArOH + NaOH (ArONa + H 2 O (Ar is an aromatic radical). Alkylation and acylation of phenolates leads to phosphorus esters - simple ArOR and complex ArOCOR (R is an organic radical). Esters can be obtained by direct reaction of phosphorus with carboxylic acids, their anhydrides, and acid chlorides. When phenols are heated with CO 2, phenolic acids are formed, for example. salicylic acid . Unlike alcohols, the hydroxyl group of F. is replaced with halogen with great difficulty. Electrophilic substitution in the phosphorus nucleus (halogenation, nitration, sulfonation, alkylation, etc.) is carried out much more easily than in unsubstituted aromatic hydrocarbons; replacement groups are sent to ortho- And pair-position to the OH group (see Orientation rules). Catalytic hydrogenation of F. leads to alicyclic alcohols, for example C 6 H 5 OH is reduced to cyclohexanol. F. is also characterized by condensation reactions, for example, with aldehydes and ketones, which are used in industry to produce phenol and resorcinol-formaldehyde resins, diphenylolpropane, and other important products.
Phosphates are obtained, for example, by hydrolysis of the corresponding halogen derivatives, alkaline melting of arylsulfonic acids ArSO 2 OH, isolated from coal tar, tar brown coals and others. F. is an important raw material in the production of various polymers, adhesives, paints and varnishes, dyes, medicines (phenolphthalein, salicylic acid, salol), surfactants and fragrant substances. Some F. are used as antiseptics and antioxidants (for example, polymers, lubricating oils). For qualitative identification of ferric chloride, solutions of ferric chloride are used, which form colored products with ferric acid. F. are toxic (see Wastewater.).
13 Alkanes
Hydrocarbons are the simplest organic compounds consisting of two elements: carbon and hydrogen. Saturated hydrocarbons, or alkanes ( international name), are called compounds whose composition is expressed general formula C n H 2n+2, where n is the number of carbon atoms. In the molecules of saturated hydrocarbons, carbon atoms are connected to each other by a simple (single) bond, and all other valences are saturated with hydrogen atoms. Alkanes are also called saturated hydrocarbons or paraffins (the term "paraffins" means "low affinity").
The first member of the homologous series of alkanes is methane CH4. The ending -an is typical for the names of saturated hydrocarbons. This is followed by ethane C 2 H 6, propane C 3 H 8, butane C 4 H 10. Starting with the fifth hydrocarbon, the name is formed from the Greek numeral, indicating the number of carbon atoms in the molecule, and the ending -an. This is pentane C 5 H 12 hexane C 6 H 14, heptane C 7 H 16, octane C 8 H 18, nonane C 9 H 20, decane C 10 H 22, etc.
In the homologous series, a gradual change in the physical properties of hydrocarbons is observed: boiling and melting points increase, density increases. Under normal conditions (temperature ~ 22°C), the first four members of the series (methane, ethane, propane, butane) are gases, from C 5 H 12 to C 16 H 34 are liquids, and from C 17 H 36 are solids.
Alkanes, starting from the fourth member of the series (butane), have isomers.
All alkanes are saturated with hydrogen to the limit (maximum). Their carbon atoms are in a state of sp 3 hybridization, which means they have simple (single) bonds.
Nomenclature
The names of the first ten members of the series of saturated hydrocarbons have already been given. To emphasize that an alkane has a straight carbon chain, the word normal (n-) is often added to the name, for example:
CH 3 -CH 2 -CH 2 -CH 3 CH 3 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 3
n-butane n-heptane
(normal butane) (normal heptane)
When a hydrogen atom is removed from an alkane molecule, single-valent particles are formed called hydrocarbon radicals (abbreviated as R). The names of monovalent radicals are derived from the names of the corresponding hydrocarbons with the ending –an replaced by –yl. Here are relevant examples:
Radicals are formed not only by organic, but also by inorganic compounds. So, if you subtract the hydroxyl group OH from nitric acid, you get a monovalent radical - NO 2, called a nitro group, etc.
When two hydrogen atoms are removed from a hydrocarbon molecule, divalent radicals are obtained. Their names are also derived from the names of the corresponding saturated hydrocarbons with the ending -ane replaced by -ylidene (if the hydrogen atoms are separated from one carbon atom) or -ylene (if the hydrogen atoms are removed from two adjacent carbon atoms). The radical CH 2 = is called methylene.
The names of radicals are used in the nomenclature of many hydrocarbon derivatives. For example: CH 3 I - methyl iodide, C 4 H 9 Cl - butyl chloride, CH 2 Cl 2 - methylene chloride, C 2 H 4 Br 2 - ethylene bromide (if bromine atoms are bonded to different carbon atoms) or ethylidene bromide (if bromine atoms are bonded to one carbon atom).
To name isomers, two nomenclatures are widely used: old - rational and modern - substitutive, which is also called systematic or international (proposed by the International Union of Pure and Applied Chemistry IUPAC).
According to rational nomenclature, hydrocarbons are considered to be derivatives of methane, in which one or more hydrogen atoms are replaced by radicals. If the same radicals are repeated several times in a formula, then they are indicated by Greek numerals: di - two, three - three, tetra - four, penta - five, hexa - six, etc. For example:
Rational nomenclature is convenient for not very complex connections.
According to substitutive nomenclature, the name is based on one carbon chain, and all other fragments of the molecule are considered as substituents. In this case, the longest chain of carbon atoms is selected and the atoms of the chain are numbered from the end to which the hydrocarbon radical is closest. Then they call: 1) the number of the carbon atom to which the radical is associated (starting with the simplest radical); 2) a hydrocarbon that has a long chain. If the formula contains several identical radicals, then before their names indicate the number in words (di-, tri-, tetra-, etc.), and the numbers of the radicals are separated by commas. Here is how hexane isomers should be called according to this nomenclature:
But more complex example:
Both substitutive and rational nomenclature are used not only for hydrocarbons, but also for other classes of organic compounds. For some organic compounds, historically established (empirical) or so-called trivial names are used (formic acid, sulfuric ether, urea, etc.).
When writing the formulas of isomers, it is easy to notice that the carbon atoms occupy different positions in them. A carbon atom that is bonded to only one carbon atom in the chain is called primary, to two is called secondary, to three is tertiary, and to four is quaternary. So, for example, in the last example, carbon atoms 1 and 7 are primary, 4 and 6 are secondary, 2 and 3 are tertiary, 5 is quaternary. The properties of hydrogen atoms, other atoms, and functional groups depend on whether they are bonded to a primary, secondary, or tertiary carbon atom. This should always be taken into account.
Receipt. Properties.
Physical properties. Under normal conditions, the first four members of the homologous series of alkanes (C 1 - C 4) are gases. Normal alkanes from pentane to heptadecane (C 5 - C 17) are liquids, starting from C 18 and above are solids. As the number of carbon atoms in the chain increases, i.e. As the relative molecular weight increases, the boiling and melting points of alkanes increase. With the same number of carbon atoms in the molecule, branched alkanes have lower boiling points than normal alkanes.
Alkanes are practically insoluble in water, since their molecules are low-polar and do not interact with water molecules; they dissolve well in non-polar organic solvents such as benzene, carbon tetrachloride, etc. Liquid alkanes are easily mixed with each other.
Basic natural springs alkanes - oil and natural gas. Various oil fractions contain alkanes from C 5 H 12 to C 30 H 62. Natural gas consists of methane (95%) with an admixture of ethane and propane.
Among the synthetic methods for producing alkanes, the following can be distinguished:
1. Obtained from unsaturated hydrocarbons. The interaction of alkenes or alkynes with hydrogen (“hydrogenation”) occurs in the presence of metal catalysts (Ni, Pd) at
heating:
CH 3 -C≡CH + 2H 2 → CH 3 -CH 2 -CH 3.
2. Preparation from halogenated conductors. When monohalogenated alkanes are heated with sodium metal, alkanes with double the number of carbon atoms are obtained (Wurtz reaction):
C 2 H 5 Br + 2Na + Br-C 2 H 5 → C 2 H 5 -C 2 H 5 + 2NaBr.
A similar reaction do not carry out with two different halogenated alkanes, since this results in a mixture of three different alkanes
3. Preparation from salts of carboxylic acids. When anhydrous salts of carboxylic acids are fused with alkalis, alkanes are obtained containing one less carbon atom compared to the carbon chain of the original carboxylic acids:
4.Obtaining methane. In an electric arc burning in a hydrogen atmosphere, a significant amount of methane is formed:
C + 2H 2 → CH 4.
The same reaction occurs when carbon is heated in a hydrogen atmosphere to 400-500 °C at high blood pressure in the presence of a catalyst.
In laboratory conditions, methane is often obtained from aluminum carbide:
Al 4 C 3 + 12H 2 O = ZSN 4 + 4Al (OH) 3.
Chemical properties. Under normal conditions, alkanes are chemically inert. They are resistant to the action of many reagents: they do not interact with concentrated sulfuric and nitric acids, with concentrated and molten alkalis, they are not oxidized by strong oxidizing agents - potassium permanganate KMnO 4, etc.
Chemical resistance alkanes due to their high strength s- C-C connections and C-H, as well as their non-polarity. Non-polar C-C and C-H bonds in alkanes are not prone to ionic cleavage, but are capable of being cleaved homolytically under the influence of active free radicals. Therefore, alkanes are characterized by radical reactions, which result in compounds where hydrogen atoms are replaced by other atoms or groups of atoms. Consequently, alkanes enter into reactions that proceed through a radical substitution mechanism, denoted by the symbol S R (from English, substitution radicalic). According to this mechanism, hydrogen atoms are most easily replaced at tertiary, then at secondary and primary carbon atoms.
1. Halogenation. When alkanes react with halogens (chlorine and bromine) under the influence of UV radiation or high temperature, a mixture of products from mono- to polyhalogen-substituted alkanes is formed. General scheme This reaction is illustrated using methane as an example:
b) Growth of the chain. The chlorine radical removes a hydrogen atom from the alkane molecule:
Cl + CH 4 →HCl + CH 3
In this case, an alkyl radical is formed, which removes a chlorine atom from the chlorine molecule:
CH 3 + Cl 2 →CH 3 Cl + Cl
These reactions are repeated until the chain breaks in one of the reactions:
Cl + Cl → Cl 2, CH 3 + CH 3 → C 2 H 6, CH 3 + Cl → CH 3 Cl
Overall reaction equation:
In radical reactions (halogenation, nitration), hydrogen atoms at tertiary carbon atoms are first mixed, then at secondary and primary carbon atoms. This is explained by the fact that the bond between the tertiary carbon atom and hydrogen is most easily broken homolytically (bond energy 376 kJ/mol), then the secondary one (390 kJ/mol), and only then the primary one (415 kJ/mol).
3. Isomerization. Normal alkanes can, under certain conditions, transform into branched-chain alkanes:
4. Cracking is the hemolytic cleavage of C-C bonds, which occurs when heated and under the influence of catalysts.
When higher alkanes are cracked, alkenes and lower alkanes are formed; when methane and ethane are cracked, acetylene is formed:
C 8 H 18 → C 4 H 10 + C 4 H 8,
2CH 4 → C 2 H 2 + ZN 2,
C 2 H 6 → C 2 H 2 + 2H 2.
These reactions are of great industrial importance. In this way, high-boiling oil fractions (fuel oil) are converted into gasoline, kerosene and other valuable products.
5. Oxidation. By mild oxidation of methane with atmospheric oxygen in the presence of various catalysts, methyl alcohol, formaldehyde, formic acid:
 |
Mild catalytic oxidation of butane with atmospheric oxygen is one of industrial methods obtaining acetic acid:
t°
2C 4 H 10 + 5O 2 → 4CH 3 COOH + 2H 2 O.
cat
In air, alkanes burn to CO 2 and H 2 O:
C n H 2n+2 + (3n+1)/2O 2 = nCO 2 + (n+1)H 2 O.
Alkenes
Alkenes (otherwise olefins or ethylene hydrocarbons) are acyclic unsaturated hydrocarbons containing one double bond between carbon atoms, forming a homologous series with the general formula CnH2n. The carbon atoms at the double bond are in the state of sp² hybridization.
The simplest alkene is ethene (C2H4). According to the IUPAC nomenclature, the names of alkenes are formed from the names of the corresponding alkanes by replacing the suffix “-ane” with “-ene”; The position of the double bond is indicated by an Arabic numeral.
Homologous series
Alkenes with more than three carbon atoms have isomers. Alkenes are characterized by isomerism of the carbon skeleton, double bond positions, interclass and geometric.
| ethene | C2H4 |
| propene | C3H6 |
| n-butene | C4H8 |
| n-pentene | C5H10 |
| n-hexene | C6H12 |
| n-heptene | C7H14 |
| n-octene | C8H16 |
| n-nonene | C9H18 |
| n-decene | C10H20 |
Physical properties
Melting and boiling points increase with molecular weight and the length of the main carbon chain.
Under normal conditions, alkenes from C2H4 to C4H8 are gases; from C5H10 to C17H34 - liquids, after C18H36 - solids. Alkenes are insoluble in water, but are highly soluble in organic solvents.
Chemical properties
Alkenes are chemically active. Their chemical properties are determined by the presence of a double bond.
Ozonolysis: the alkene is oxidized to aldehydes (in the case of monosubstituted vicinal carbons), ketones (in the case of disubstituted vicinal carbons) or a mixture of aldehyde and ketone (in the case of a tri-substituted alkene at the double bond):
R1–CH=CH–R2 + O3 → R1–C(H)=O + R2C(H)=O + H2O
R1–C(R2)=C(R3)–R4+ O3 → R1–C(R2)=O + R3–C(R4)=O + H2O
R1–C(R2)=CH–R3+ O3 → R1–C(R2)=O + R3–C(H)=O + H2O
Ozonolysis under harsh conditions - the alkene is oxidized to acid:
R"–CH=CH–R" + O3 → R"–COOH + R"–COOH + H2O
Double connection connection:
CH2=CH2 +Br2 → CH2Br-CH2Br
Oxidation with peracids:
CH2=CH2 + CH3COOOH →
or
CH2=CH2 + HCOOH → HOCH2CH2OH
First arose in early XIX V. radical theory(J. Gay-Lussac, F. Wehler, J. Liebig). Radicals are groups of atoms that pass without change during chemical reactions from one compound to another. This concept of radicals has been preserved, but most other provisions of the theory of radicals turned out to be incorrect.
According to type theories(C. Gerard) all organic substances can be divided into types corresponding to certain inorganic substances. For example, alcohols R-OH and simple esters R-O-R were considered as representatives of the H-OH type of water, in which the hydrogen atoms are replaced by radicals. The theory of types created a classification of organic substances, some of the principles of which are used today.
The modern theory of the structure of organic compounds was created by the outstanding Russian scientist A.M. Butlerov.
Basic principles of the theory of the structure of organic compounds A.M. Butlerov
1. Atoms in a molecule are arranged in a certain sequence according to their valence. The valency of the carbon atom in organic compounds is four.
2. The properties of substances depend not only on which atoms and in what quantities are included in the molecule, but also on the order in which they are connected to each other.
3. Atoms or groups of atoms that make up a molecule mutually influence each other, which determines the chemical activity and reactivity of the molecules.
4. Studying the properties of substances allows us to determine their chemical structure.
The mutual influence of neighboring atoms in molecules is the most important property of organic compounds. This influence is transmitted either through a chain of simple bonds or through a chain of conjugated (alternating) simple and double bonds.
Classification of organic compounds is based on the analysis of two aspects of the structure of molecules - the structure of the carbon skeleton and the presence of functional groups.
Organic compounds
Hydrocarbons Heterocyclic compounds
Limit - Unprecedented - Aroma -
efficient practical
Aliphatic Carbocyclic
Ultimate Unsaturated Alicyclic Aromatic
(Alkanes) (Cycloalkanes) (Arenas)
WITH P H 2 P+2 C P H 2 P WITH P H 2 P-6
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All topics in this section:
Alkenes Alkadienes Alkynes
SpN2p SpN2p-2 SpN2p-2 Fig. 1. Classification of organic compounds by structure
Electronic structure of the carbon atom. Hybridization.
For the valence electron layer of the C atom, located in the main subgroup of the fourth group of the second period of D. I. Mendeleev’s Periodic Table, the main quantum number n = 2, secondary (orbital
Conjugate systems
There are two types of conjugate systems (and couplings).
1. p, p-conjugation - electrons are delocalized
TOPIC 3. Chemical structure and isomerism of organic compounds
Isomerism of organic compounds.
The rotation around the C–C s-bond is relatively easy; the hydrocarbon chain can take different shapes. Conformational forms easily transform into each other and therefore are not different compounds
Conformations of cyclic compounds.
Cyclopentane. The five-membered ring in flat form has bond angles of 108°, which is close to normal value for sp3-hybrid atom. Therefore, in flat cyclopentane, in contrast to the cycle
Configuration isomers
These are stereoisomers with different arrangements around certain atoms of other atoms, radicals or functional groups in space relative to each other.
There are concepts of diastere
General characteristics of reactions of organic compounds. Acidity and basicity of organic compounds. To assess the acidity and basicity of organic compounds
highest value
have two theories - the Brønsted theory and theo
Bronsted bases are neutral molecules or ions that can accept a proton (proton acceptors).
Acidity and basicity are not absolute, but relative properties of compounds: acidic properties are detected only in the presence of a base; basic properties - only in the presence of ki
General characteristics of reactions of organic compounds
Most organic reactions involve several sequential (elementary) steps. A detailed description of the totality of these stages is called a mechanism. Reaction mechanism -
Selectivity of reactions
In many cases, an organic compound contains several unequal reaction centers. Depending on the structure of the reaction products, they speak of regioselectivity, chemoselectivity, and
Radical reactions.
Chlorine reacts with saturated hydrocarbons only under the influence of light, heat or in the presence of catalysts, and all hydrogen atoms are successively replaced by chlorine: CH4
Electrophilic addition reactions
Unsaturated hydrocarbons - alkenes, cycloalkenes, alkadienes and alkynes - exhibit the ability to undergo addition reactions, since they contain double or triple bonds. More important in vivo is twofold
And elimination from a saturated carbon atom
Let us consider the mechanism of reactions of this type using the example of the interaction of carboxylic acids with alcohols (esterification reaction). In the carboxyl group of the acid, it is realized p,p- pairing, since a couple of elements
Nucleophilic substitution reactions in the series of carboxylic acids.
Only from a purely formal point of view can the carboxyl group be considered as a combination of carbonyl and hydroxyl functions. In fact, their mutual influence on each other is such that completely and
Organic compounds.
Oxidation-reduction reactions (ORR) occupy great place in organic chemistry. Essential have OVR for vital processes. With their help, the body will satisfy
Participating in life processes
The vast majority of organic substances involved in metabolic processes are compounds with two or more functional groups. Such compounds are usually classified
Diatomic phenols
Diatomic phenols - pyrocatechol, resorcinol, hydroquinone - are part of many natural compounds. All of them give a characteristic staining with ferric chloride. Pyrocatechol (o-dihydroxybenzene, catecho
Dicarboxylic and unsaturated carboxylic acids.
Carboxylic acids containing one carboxyl group are called monobasic, two are called dibasic, etc. Dicarboxylic acids are white crystalline substances, having
Amino alcohols
2-Aminoethanol (ethanolamine, colamine) is a structural component of complex lipids, formed by opening the tense three-membered rings of ethylene oxide and ethyleneimine with ammonia or water, respectively.
Hydroxy and amino acids.
Hydroxy acids contain both hydroxyl and carboxyl groups in the molecule, amino acids contain carboxyl and amino groups.
Depending on the location of the hydroxy or amino group
Oxoacids
Oxoacids are compounds containing both carboxyl and aldehyde (or ketone) groups. In accordance with this, aldehyde acids and keto acids are distinguished.
The simplest aldehyde acid Heterofunctional benzene derivatives as medicines. Recent decades have been characterized by the emergence of many new medicines and drugs. At the same time
great importance
continue to preserve some groups of previously known medicinal drugs
TOPIC 11. Amino acids, peptides, proteins
Structure and properties of amino acids and peptides.
Amino acids are compounds in whose molecules amino and carboxyl groups are simultaneously present. Natural a-amine
Spatial structure of polypeptides and proteins For high molecular weight polypeptides and proteins along with primary structure more typical high levels
organizations that are commonly called secondary, tertiary and quaternary structures.
TOPIC 12. Carbohydrates: mono, di- and polysaccharides
Carbohydrates are divided into simple (monosaccharides) and complex (polysaccharides).
Monosaccharides (monoses). These are heteropolyfunctional compounds containing carbonyl and several g
TOPIC 13. Nucleotides and nucleic acids
Nucleic acids (polynucleotides) are biopolymers whose monomer units are nucleotides.
The nucleotide is a three-component structure consisting
Nucleosides.
Heterocyclic bases form N-glycosides with D-ribose or 2-deoxy-D-ribose. In nucleic acid chemistry, such N-glycosides are called nucleosides. D-ribose and 2-deoxy-D-ribose in p
Nucleotides.
Nucleotides are called phosphates of nucleosides. Phosphoric acid usually esterifies the alcohol hydroxyl at C-5" or C-3" in a ribose or deoxyribose residue (the atoms of the nitrogenous base ring are numbered
Steroids Steroids are widely distributed in nature and perform a variety of functions in the body. To date, about 20,000 steroids are known; more than 100 of them are used in medicine. Steroids have Steroid hormones Hormones - biologically active substances
formed as a result of the activity of glands
internal secretion
and taking part in the regulation of metabolism and physiological functions in the body.
Sterols As a rule, the cells are very rich in sterols. Depending on the source of isolation, zoosterols (from animals), phytosterols (from plants), mycosterols (from fungi) and sterols of microorganisms are distinguished. IN Bile acids
In the liver, sterols, particularly cholesterol, are converted into bile acids. Aliphatic side chain at C17
bile acids
, derivatives of the hydrocarbon cholane, consists of 5 carbon atoms
Terpenes and terpenoids This name combines a number of hydrocarbons and their oxygen-containing derivatives - alcohols, aldehydes and ketones, the carbon skeleton of which is built from two, three or more isoprene units. Sami in the food of humans and animals is necessary for their normal functioning.
This is a classic op.
Fat-soluble vitamins Vitamin A is a sesquiterpene and is found in butter, milk, egg yolk
, fish oil; lard and margarine do not contain it. This is a growth vitamin; lack of it in food causes
Water-soluble vitamins
At the end of the last century, thousands of sailors on Japanese ships suffered, and many of them died painful deaths from the mysterious beriberi disease. One of the mysteries of beriberi was that the sailors on the Lesson content:
Theories of the structure of organic compounds: prerequisites for their creation, basic principles. Chemical structure as the order of connection and mutual influence of atoms in molecules. Homology, isomerism. Dependence of the properties of substances on the chemical structure. Main directions of development of the theory of chemical structure. The dependence of the appearance of toxicity in organic compounds on the composition and structure of their molecules (the length of the carbon chain and the degree of its branching, the presence of multiple bonds, the formation of cycles and peroxide bridges, the presence of halogen atoms), as well as on the solubility and volatility of the compound.
- Lesson objectives:
- Organize student activities to familiarize and initially consolidate the basic principles of the theory of chemical structure.
Show students the universal nature of the theory of chemical structure using the example of inorganic isomers and the mutual influence of atoms in inorganic substances.
During the classes:
1. Organizational moment.
2. Updating students' knowledge.
1) What does organic chemistry study?
2) What substances are called isomers?
3) What substances are called homologues?
4) Name the theories known to you that arose in organic chemistry at the beginning of the 19th century.
5) What shortcomings did the theory of radicals have?
6) What shortcomings did type theory have?
3. Setting goals and objectives for the lesson.
The concept of valency formed an important part of A.M.’s theory of chemical structure. Butlerov in 1861 Periodic law
, formulated by D.I. Mendeleev in 1869, revealed the dependence of the valency of an element on its position in the periodic table.
Scientists from many countries, with their work, have paved the way for the creation of a theory explaining the structure and properties of organic substances.
At a congress of German naturalists and doctors in the city of Speyer, a report was read entitled “Something in the chemical structure of bodies.” The author of the report was Kazan University professor Alexander Mikhailovich Butlerov. It was this very “something” that constituted the theory of chemical structure, which formed the basis of our modern ideas about chemical compounds.
Organic chemistry received a solid scientific basis, which ensured its rapid development in the next century until the present day. This theory made it possible to predict the existence of new compounds and their properties. The concept of chemical structure made it possible to explain such mysterious phenomenon, like isomerism.
The main principles of the theory of chemical structure are as follows:
1. Atoms in molecules of organic substances are combined in a certain sequence according to their valency.
2. The properties of substances are determined by the qualitative, quantitative composition, order of connection and mutual influence of atoms and groups of atoms in the molecule.
3. The structure of molecules can be established based on the study of their properties.
Let's consider these provisions in more detail. Molecules of organic substances contain atoms of carbon (valence IV), hydrogen (valence I), oxygen (valency II), nitrogen (valency III). Each carbon atom in molecules of organic substances forms four chemical bonds with other atoms, and carbon atoms can be connected in chains and rings. Based on the first principle of the theory of chemical structure, we will draw up structural formulas of organic substances. For example, it has been established that methane has the composition CH4. Taking into account the valences of carbon and hydrogen atoms, only one structural formula of methane can be proposed:
The chemical structure of other organic substances can be described by the following formulas:
The second position of the theory of chemical structure describes the relationship known to us: composition - structure - properties. Let's see the manifestation of this pattern using the example of organic substances.
Ethane and ethyl alcohol have different high-quality composition. The alcohol molecule, unlike ethane, contains an oxygen atom. How will this affect the properties?
The introduction of an oxygen atom into a molecule dramatically changes the physical properties of the substance. This confirms the dependence of properties on the qualitative composition.
Let's compare the composition and structure of the hydrocarbons methane, ethane, propane and butane.
Methane, ethane, propane and butane have the same qualitative composition, but different quantitative ones (the number of atoms of each element). According to the second position of the theory of chemical structure, they should have different properties.
| Substance | Boiling temperature,°C | Melting temperature,°C |
| CH 4 | – 182,5 | – 161,5 |
| C 2 H 6 | – 182,8 | – 88,6 |
| C 3 H 8 | – 187,6 | – 42,1 |
| C 4 H 10 | – 138,3 | – 0,5 |
As can be seen from the table, with an increase in the number of carbon atoms in a molecule, the boiling and melting temperatures increase, which confirms the dependence of the properties on the quantitative composition of the molecules.
The molecular formula C4H10 corresponds not only to butane, but also to its isomer isobutane:
Isomers have the same qualitative (carbon and hydrogen atoms) and quantitative (4 carbon atoms and ten hydrogen atoms) composition, but differ from each other in the order of connection of atoms (chemical structure). Let's see how the difference in the structure of isomers will affect their properties.
A branched hydrocarbon (isobutane) has more high temperatures boiling and melting than a hydrocarbon of normal structure (butane). This can be explained by the closer proximity of molecules to each other in butane, which increases the forces of intermolecular attraction and, therefore, requires more energy to separate them.
The third position of the theory of chemical structure shows the feedback between the composition, structure and properties of substances: composition - structure - properties. Let's consider this using the example of compounds with the composition C 2 H 6 O.
Let's imagine that we have samples of two substances with the same molecular formula C 2 H 6 O, which was determined during qualitative and quantitative analysis. But how can we find out the chemical structure of these substances? Studying their physical and chemical properties will help answer this question. When the first substance interacts with metallic sodium, the reaction does not occur, but the second actively interacts with it, releasing hydrogen. Let us determine the quantitative ratio of substances in the reaction. To do this, add a certain mass of sodium to the known mass of the second substance. Let's measure the volume of hydrogen. Let's calculate the amounts of substances. In this case, it turns out that from two moles of the substance under study, one mole of hydrogen is released. Therefore, each molecule of this substance is the source of one hydrogen atom. What conclusion can be drawn? Only one hydrogen atom differs in properties and, therefore, in structure (which atoms it is associated with) from all the others. Taking into account the valence of carbon, hydrogen and oxygen atoms, only one formula can be proposed for a given substance:
For the first substance, a formula can be proposed in which all hydrogen atoms have the same structure and properties:
A similar result can be obtained by studying physical properties these substances.
Thus, based on studying the properties of substances, we can draw a conclusion about its chemical structure.
The importance of the theory of chemical structure can hardly be overestimated. She armed the chemists scientific basis to study the structure and properties of organic substances. The Periodic Law formulated by D.I. has a similar meaning. Mendeleev. The theory of structure summarized everything scientific views, prevailing in chemistry of that time. Scientists were able to explain the behavior of organic substances during chemical reactions. Based on the theory of A.M. Butlerov predicted the existence of isomers of some substances, which were later obtained. Just like the Periodic Law, the theory of chemical structure received its further development after the formation of the theory of atomic structure, chemical bonding and stereochemistry.
Created by A.M. Butlerov in the 60s of the 19th century, the theory of the chemical structure of organic compounds brought the necessary clarity to the reasons for the diversity of organic compounds, revealed the relationship between the structure and properties of these substances, made it possible to explain the properties of already known and predict the properties of yet undiscovered organic compounds.
Discoveries in the field of organic chemistry (tetravalency of carbon, the ability to form long chains) allowed Butlerov in 1861 to formulate the main generations of the theory:
1) Atoms in molecules are connected according to their valence (carbon-IV, oxygen-II, hydrogen-I), the sequence of atom connections is reflected by structural formulas.
2) The properties of substances depend not only on chemical composition, but also on the order of connection of atoms in the molecule (chemical structure). Exist isomers, that is, substances that have the same quantitative and qualitative composition, but different structures, and, therefore, different properties.
C 2 H 6 O: CH 3 CH 2 OH - ethyl alcohol and CH 3 OCH 3 - dimethyl ether
C 3 H 6 – propene and cyclopropane - CH 2 =CH−CH 3
3) Atoms mutually influence each other, this is a consequence of the different electronegativity of the atoms forming the molecules (O>N>C>H), and these elements have different effects on the displacement of common electron pairs.
4) Based on the structure of a molecule of an organic substance, one can predict its properties, and based on its properties, one can determine its structure.
Further development TSOS received after establishing the structure of the atom, adopting the concept of types chemical bonds, about types of hybridization, discovery of the phenomenon of spatial isomerism (stereochemistry).
Ticket No. 7 (2)
Electrolysis as a redox process. Electrolysis of melts and solutions using sodium chloride as an example. Practical use electrolysis.
Electrolysis- this is a redox process that occurs on the electrodes during the passage of a constant electric current through a melt or electrolyte solution
The essence of electrolysis is the implementation of chemical reactions using electrical energy. The reactions are reduction at the cathode and oxidation at the anode.
The cathode(-) gives electrons to the cations, and the anode(+) accepts electrons from the anions.
NaCl melt electrolysis
NaCl-―>Na + +Cl -
K(-): Na + +1e-―>Na 0 | 2 percent recovery
A(+) :2Cl-2e-―>Cl 2 0 | 1 percent oxidation
2Na + +2Cl - -―>2Na+Cl 2
Electrolysis aqueous solution NaCl
In the electrolysis of NaC| Na + and Cl - ions, as well as water molecules, participate in water. When a current passes, Na + cations move towards the cathode, and Cl - anions move towards the anode. But at the cathode Instead of Na ions, water molecules are reduced:
2H 2 O + 2e-―> H 2 +2OH -
and chloride ions are oxidized at the anode:
2Cl - -2e-―>Cl 2
As a result, there is hydrogen at the cathode, chlorine at the anode, and NaOH accumulates in the solution
In ionic form: 2H 2 O+2e-―>H 2 +2OH-
2Cl - -2e-―>Cl 2
electrolysis
2H 2 O+2Cl - -―>H 2 +Cl 2 +2OH -
electrolysis
In molecular form: 2H 2 O+2NaCl-―> 2NaOH+H 2 +Cl 2
Application of electrolysis:
1)Protection of metals from corrosion
2) Obtaining active metals (sodium, potassium, alkaline earth, etc.)
3) Purification of certain metals from impurities (electric refining)
Ticket No. 8 (1)
Related information:
- A) Theory of knowledge is a science that studies the forms, methods and techniques of the emergence and patterns of development of knowledge, its relationship to reality, the criteria of its truth.