There are many organic compounds, but among them there are compounds with common and similar properties. Therefore they all common features classified, combined into separate classes and groups. The classification is based on hydrocarbons – compounds that consist only of carbon and hydrogen atoms. Other organic substances belong to "Other classes organic compounds».
Hydrocarbons are divided into two large classes: acyclic and cyclic compounds.
Acyclic compounds (fatty or aliphatic) – compounds whose molecules contain an open (not closed in a ring) straight or branched carbon chain with single or multiple bonds. Acyclic compounds are divided into two main groups:
saturated (saturated) hydrocarbons (alkanes), in which all carbon atoms are connected to each other only by simple bonds;
unsaturated (unsaturated) hydrocarbons, in which between carbon atoms, in addition to single simple bonds, there are also double and triple bonds.
Unsaturated (unsaturated) hydrocarbons are divided into three groups: alkenes, alkynes and alkadienes.
Alkenes(olefins, ethylene hydrocarbons) – acyclic unsaturated hydrocarbons, which contain one double bond between carbon atoms, form homologous series with the general formula C n H 2n. The names of alkenes are formed from the names of the corresponding alkanes with the suffix “-ane” replaced by the suffix “-ene”. For example, propene, butene, isobutylene or methylpropene.
Alkynes(acetylene hydrocarbons) – hydrocarbons that contain a triple bond between carbon atoms form a homologous series with the general formula CnH2n-2. The names of alkenes are formed from the names of the corresponding alkanes, replacing the suffix “-an” with the suffix “-in”. For example, ethine (acytelene), butine, peptin.
Alcadienes – organic compounds that contain two carbon-carbon double bonds. Depending on how the double bonds are positioned relative to each other, dienes are divided into three groups: conjugated dienes, allenes, and dienes with isolated double bonds. Typically, dienes include acyclic and cyclic 1,3-dienes, forming with the general formulas C n H 2n-2 and C n H 2n-4. Acyclic dienes are structural isomers of alkynes.
Cyclic compounds, in turn, are divided into two large groups:
- carbocyclic compounds – compounds whose cycles consist only of carbon atoms; Carbocyclic compounds are divided into alicyclic – saturated (cycloparaffins) and aromatic;
- heterocyclic compounds – compounds whose cycles consist not only of carbon atoms, but atoms of other elements: nitrogen, oxygen, sulfur, etc.
In molecules of both acyclic and cyclic compounds Hydrogen atoms can be replaced by other atoms or groups of atoms, thus, by introducing functional groups, hydrocarbon derivatives can be obtained. This property further expands the possibilities of obtaining various organic compounds and explains their diversity.
The presence of certain groups in the molecules of organic compounds determines the commonality of their properties. This is the basis for the classification of hydrocarbon derivatives.
"Other Classes of Organic Compounds" include the following:
Alcohols are obtained by replacing one or more hydrogen atoms with hydroxyl groups – OH. It is a compound with the general formula R – (OH)x, where x – number of hydroxyl groups.
Aldehydes contain an aldehyde group (C=O), which is always located at the end of the hydrocarbon chain.
Carboxylic acids contain one or more carboxyl groups – COOH.
Esters – derivatives of oxygen-containing acids, which are formally products of substitution of hydrogen atoms of hydroxides – OH acidic function on a hydrocarbon residue; are also considered as acyl derivatives of alcohols.
Fats (triglycerides) – natural organic compounds, complete esters glycerol and monocomponent fatty acids; belong to the class of lipids. Natural fats contain three acid radicals with an unbranched structure and, usually, even number carbon atoms.
Carbohydrates – organic substances that contain a straight chain of several carbon atoms, a carboxyl group and several hydroxyl groups.
Amines contain an amino group – NH 2
Amino acids– organic compounds whose molecule simultaneously contains carboxyl and amine groups.
Squirrels – high-molecular organic substances that consist of alpha amino acids connected in a chain by a peptide bond.
Nucleic acids – high molecular weight organic compounds, biopolymers formed by nucleotide residues.
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All organic compounds, depending on the nature of the carbon skeleton, can be divided into acyclic and cyclic.
Acyclic (non-cyclic, chain) compounds are also called fatty or aliphatic. These names are due to the fact that one of the first well-studied compounds of this type were natural fats. Among acyclic compounds, limit ones are distinguished, for example:
and unlimited, for example:
Among the cyclic compounds usually distinguished carbo-cyclic, whose molecules contain rings of carbon atoms, and heterocyclic, the rings of which contain, in addition to carbon, atoms of other elements (oxygen, sulfur, nitrogen, etc.).
Carbocyclic compounds are divided into alicyclic (saturated and unsaturated), similar in properties to aliphatic ones, and aromatic, which contain benzene rings.
The considered classification of organic compounds can be presented in the form of a brief diagram
In addition to carbon and hydrogen, many organic compounds also contain other elements, and in the form of functional groups - groups of atoms that determine chemical properties of this class of connections. The presence of these groups makes it possible to subdivide the above types of organic compounds into classes and facilitate their study. Some of the most characteristic functional groups and the corresponding classes of compounds are given in the table
|
Functional |
Name groups |
Classes connections |
|
|
—OH |
Hydroxide Carbonyl |
Alcohols |
C2H5OH Ethanol |
|
Aldehydes |
acetaldehyde |
||
| ketones |
|
||
|
Carboxyl |
Carbon |
||
| —NO 2 | Nitro group | Nitro compounds |
CH3NO2 Nitrometpn |
|
—NH 2 |
You start studying organic chemistry, which we only became a little familiar with in 9th grade. Why "organic"? Let's turn to history.
Even at the turn of the 9th-10th centuries. Arab alchemist Abu Bakr ar-Razi (865-925) first divided everything chemicals according to their origin into three kingdoms: mineral, plant and animal substances. This unique classification lasted for almost a thousand years.
However, in early XIX V. There was a need to combine the chemistry of substances of plant and animal origin into a single science. This approach will seem logical to you if you have at least elementary representations about the composition of living organisms.
From the science course and initial courses biology, you know that the composition of any living cell, both plant and animal, necessarily includes proteins, fats, carbohydrates and other substances that are commonly called organic. At the suggestion of the Swedish chemist J. Ya. Berzelius, from 1808 the science that studies organic substances began to be called organic chemistry.
The idea of the chemical unity of living organisms on Earth delighted scientists so much that they even created a beautiful but false doctrine - vitalism, according to which it was believed that in order to obtain (synthesize) organic compounds from inorganic ones, a special “vital force” (vis vitalis) was needed. Scientists believed that vitality is an obligatory attribute of only living organisms. This led to the false conclusion that the synthesis of organic compounds from inorganic ones outside living organisms - in test tubes or industrial installations - is impossible.
Vitalists reasonably argued that the most important fundamental synthesis on our planet - photosynthesis (Fig. 1) is impossible outside of green plants.
Rice. 1.
Photosynthesis
In a simplified way, the process of photosynthesis is described by the equation
According to the vitalists, any other syntheses of organic compounds outside living organisms are also impossible. However, the further development of chemistry and the accumulation of new scientific facts proved that the vitalists were deeply mistaken.
In 1828, the German chemist F. Wöhler synthesized the organic compound urea from the inorganic substance ammonium cyanate. The French scientist M. Berthelot obtained fat in a test tube in 1854. In 1861, the Russian chemist A.M. Butlerov synthesized a sugary substance. Vitalism has failed.
Nowadays organic chemistry is a rapidly developing industry chemical science and production. Currently, there are more than 25 million organic compounds, among which there are substances that are up to today have not been found in wildlife. The production of these substances became possible thanks to the results scientific activity organic chemists.
All organic compounds can be divided into three types based on their origin: natural, artificial and synthetic.
Natural organic compounds- these are waste products of living organisms (bacteria, fungi, plants, animals). These are proteins, fats, carbohydrates, vitamins, hormones, enzymes, natural rubber, etc. that are well known to you (Fig. 2).
Rice. 2.
Natural organic compounds:
1-4 - in fibers and fabrics (woolen 1, silk 2, linen 3, cotton 4); 5-10 - in food products (milk 5, meat 6, fish 7, vegetable and butter 8, vegetables and fruits 9, cereals and bread 10); 11, 12 - in fuel and raw materials for the chemical industry (natural gas 11, oil 12); 13 - in wood
Artificial organic compounds- these are products of chemically transformed natural substances into compounds that are not found in living nature. Thus, based on the natural organic compound cellulose, artificial fibers (acetate, viscose, copper-ammonia), non-flammable film and photographic films, plastics (celluloid), smokeless powder, etc. are produced (Fig. 3).
Rice. 3. Products and materials made on the basis of artificial organic compounds: 1.2 - artificial fibers and fabrics; 3 - plastic (celluloid); 4 - photographic film; 5 - smokeless powder
Synthetic organic compounds obtained synthetically, that is, by combining simpler molecules into more complex ones. These include, for example, synthetic rubbers, plastics, drugs, synthetic vitamins, growth stimulants, plant protection products, etc. (Fig. 4).
Rice. 4.
Products and materials made from synthetic organic compounds:
1 - plastics; 2 - medicines; 3 - detergents; 4 - synthetic fibers and fabrics; 5 - paints, enamels and adhesives; 6 - insect control agents; 7 - fertilizers; 8 - synthetic rubbers
Despite the enormous diversity, all organic compounds contain carbon atoms. Therefore, organic chemistry can be called the chemistry of carbon compounds.
Along with carbon, most organic compounds contain hydrogen atoms. These two elements form a number of classes of organic compounds, which are called hydrocarbons. All other classes of organic compounds can be considered as derivatives of hydrocarbons. This allowed the German chemist K. Schorlemmer to give classic definition organic chemistry, which has not lost its significance more than 120 years later.
For example, when replacing one hydrogen atom in an ethane molecule C 2 H 6 with a hydroxyl group -OH, the familiar one is formed ethanol C 2 H 5 OH, and when replacing the hydrogen atom in the methane molecule CH 4 with the carboxyl group -COOH, acetic acid CH 3 COOH is formed.
Why, from more than a hundred elements Periodic table D.I. Mendeleev, it was carbon that became the basis of all living things? Much will become clear to you if you read the following words of D.I. Mendeleev, written by him in the textbook “Fundamentals of Chemistry”: “Carbon is found in nature both in a free and in a connecting state, in very various forms and types... The ability of carbon atoms to connect with each other and give complex particles is manifested in all carbon compounds... In none of the elements... is the ability for complication developed to the same extent as in carbon... Not a single pair of elements does not produce as many compounds as carbon and hydrogen.”
The chemical bonds of carbon atoms with each other and with atoms of other elements (hydrogen, oxygen, nitrogen, sulfur, phosphorus) that make up organic compounds can be destroyed under the influence of natural factors. Therefore, carbon undergoes a continuous cycle in nature: from the atmosphere (carbon dioxide) - into plants (photosynthesis), from plants - into animal organisms, from living - into non-living, from non-living - into living (Fig. 5).
Rice. 5.
Carbon cycle in nature
And in conclusion, we note a number of features characterizing organic compounds.
Since the molecules of all organic compounds contain carbon atoms, and almost all contain hydrogen atoms, most of them are flammable and, as a result of combustion, form carbon monoxide (IV) (carbon dioxide) and water.
Unlike not organic matter, of which there are about 500 thousand, organic compounds are more diverse, so their number now amounts to more than 25 million.
Many organic compounds are more complex than inorganic substances, and many of them have a huge molecular weight, such as proteins, carbohydrates, nucleic acids, i.e. substances due to which life processes occur.
Organic compounds are usually formed due to covalent bonds and therefore have a molecular structure, and therefore have low melting and boiling points, and are thermally unstable.
New words and concepts
- Vitalism.
- Photosynthesis.
- Organic compounds: natural, artificial and synthetic.
- Organic chemistry.
- Features characterizing organic compounds.
Questions and tasks
- Using knowledge from the biology course, compare chemical composition plant and animal cells. What organic compounds do they contain? How do the organic compounds of plant and animal cells differ?
- Describe the carbon cycle in nature.
- Explain why the doctrine of vitalism arose and how it failed.
- What types of organic compounds (by origin) do you know? Give examples and indicate areas of their application.
- Calculate the volume of oxygen (no.) and the mass of glucose formed as a result of photosynthesis from 880 tons of carbon dioxide.
- Calculate the volume of air (n.a.) that will be required to burn 480 kg of CH4 methane if the volume fraction of oxygen in the air is 21%.
>> Chemistry: Classification of organic compounds
You already know 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 an organic substance molecule is its skeleton - a chain of carbon atoms. Depending on the order of connection of carbon atoms in this chain, substances are divided into acyclic, which do not contain closed chains of carbon atoms in molecules, and carbocyclic, containing such chains (cycles) in molecules.
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