Carbon monoxide(II ), or carbon monoxide, CO was discovered by the English chemist Joseph Priestley in 1799. It is a colorless gas, tasteless and odorless, it is slightly soluble in water (3.5 ml in 100 ml of water at 0 ° C), has low melting points (-205 °C) and boiling points (-192 °C).

Carbon monoxide enters the Earth's atmosphere during incomplete combustion of organic substances, during volcanic eruptions, and also as a result of the vital activity of some lower plants (algae). The natural level of CO in the air is 0.01-0.9 mg/m 3 . Carbon monoxide very poisonous. In the human body and higher animals, it actively reacts with

The flame of burning carbon monoxide is a beautiful blue-violet color. It is easy to observe for yourself. To do this, you need to light a match. The lower part of the flame is luminous - this color is given to it by hot particles of carbon (a product of incomplete combustion of wood). From above, the flame is surrounded by a blue-violet border. This burns carbon monoxide formed during the oxidation of wood.

a complex compound of iron - the blood heme (associated with the glo-bin protein), disrupting the functions of oxygen transfer and consumption by tissues. In addition, it enters into an irreversible interaction with some enzymes involved in the energy metabolism of the cell. At a concentration of carbon monoxide in a room of 880 mg / m 3, death occurs after a few hours, and at 10 g / m 3 - almost instantly. The maximum permissible content of carbon monoxide in the air is 20 mg / m 3. The first signs of CO poisoning (at a concentration of 6-30 mg / m 3) are a decrease in the sensitivity of vision and hearing, headache, and a change in heart rate. If a person is poisoned by carbon monoxide, he must be taken to fresh air, artificial respiration should be given to him, in mild cases of poisoning, strong tea or coffee should be given.

Large amounts of carbon monoxide ( II ) enter the atmosphere as a result of human activities. Thus, a car on average emits about 530 kg of CO2 into the air per year. When burning in the engine internal combustion 1 liter of gasoline carbon monoxide emission ranges from 150 to 800 g. On the highways of Russia, the average concentration of CO is 6-57 mg / m 3, that is, it exceeds the poisoning threshold. Carbon monoxide accumulates in poorly ventilated front yards near motorways, in basements and garages. In recent years, special points have been organized on the roads to control the content of carbon monoxide and other products of incomplete combustion of fuel (CO-CH-control).

At room temperature, carbon monoxide is fairly inert. It does not interact with water and alkali solutions, i.e., it is a non-salt-forming oxide, however, when heated, it reacts with solid alkalis: CO + KOH \u003d HSOOK (potassium formate, salt of formic acid); CO + Ca (OH) 2 \u003d CaCO 3 + H 2. These reactions are used to release hydrogen from synthesis gas (CO + 3H 2), which is formed during the interaction of methane with superheated water vapor.

An interesting property of carbon monoxide is its ability to form compounds with transition metals - carbonyls, for example: Ni +4CO ® 70°C Ni(CO) 4 .

Carbon monoxide(II ) is an excellent reducing agent. When heated, it is oxidized by atmospheric oxygen: 2CO + O 2 \u003d 2CO 2. This reaction can also be carried out at room temperature using a catalyst - platinum or palladium. Such catalysts are installed on cars to reduce CO emissions into the atmosphere.

The reaction of CO with chlorine produces a very poisonous gas, phosgene (t kip \u003d 7.6 ° С): CO + Cl 2 \u003d COCl 2 . Previously, it was used as a chemical warfare agent, and now it is used in the production of synthetic polyurethane polymers.

Carbon monoxide is used in the smelting of iron and steel for the reduction of iron from oxides; it is also widely used in organic synthesis. During the interaction of a mixture of carbon oxide ( II ) with hydrogen, depending on the conditions (temperature, pressure), various products are formed - alcohols, carbonyl compounds, carboxylic acids. Of particular importance is the reaction of methanol synthesis: CO + 2H 2 \u003d CH3OH , which is one of the main products of organic synthesis. Carbon monoxide is used to synthesize the phos-gene, formic acid, as a high-calorie fuel.

Carbon monoxide, carbon monoxide (CO) is a colorless, odorless and tasteless gas that is slightly less dense than air. It is toxic to hemoglobin animals (including humans) if its concentrations are above about 35 ppm, although it is also produced in normal animal metabolism in small amounts, and is thought to have some normal biological functions. In the atmosphere, it is spatially variable and rapidly decaying, and has a role in the formation of ozone at ground level. Carbon monoxide is made up of one carbon atom and one oxygen atom linked by a triple bond, which consists of two covalent bonds, as well as one dative covalent bond. This is the simplest carbon monoxide. It is isoelectronic with the cyanide anion, the nitrosonium cation, and molecular nitrogen. In coordination complexes, the carbon monoxide ligand is called the carbonyl.

Story

Aristotle (384-322 BC) first described the process of burning coal, which leads to the formation of toxic fumes. In ancient times, there was a method of execution - to close the criminal in a bathroom with smoldering coals. However, at that time the mechanism of death was unclear. The Greek physician Galen (AD 129-199) suggested that there was a change in the composition of the air that harmed a person when inhaled. In 1776, the French chemist de Lasson produced CO by heating zinc oxide with coke, but the scientist erroneously concluded that the gaseous product was hydrogen because it burned with a blue flame. The gas was identified as a compound containing carbon and oxygen by the Scottish chemist William Cumberland Cruikshank in 1800. Its toxicity in dogs was thoroughly investigated by Claude Bernard around 1846. During World War II, a gas mixture containing carbon monoxide was used to fuel motor vehicles operating in parts of the world where gasoline and diesel were scarce. External (with some exceptions) charcoal or wood-derived gas generators were installed and a mixture of atmospheric nitrogen, carbon monoxide and small amounts of other gasification gases was fed to the gas mixer. The gas mixture resulting from this process is known as wood gas. Carbon monoxide was also used on a large scale during the Holocaust in some German Nazi death camps, most notably in the Chelmno gas vans and in the T4 "euthanasia" killing program.

Sources

Carbon monoxide is formed during the partial oxidation of carbon-containing compounds; it forms when there is not enough oxygen to produce carbon dioxide (CO2), such as when working on a stove or internal combustion engine, in an enclosed space. In the presence of oxygen, including atmospheric concentrations, carbon monoxide burns with a blue flame, producing carbon dioxide. Coal gas, which was widely used until the 1960s for indoor lighting, cooking and heating, contained carbon monoxide as a significant fuel constituent. Some processes in modern technology, such as iron smelting, still produce carbon monoxide as a by-product. Worldwide, the largest sources of carbon monoxide are natural sources, due to photochemical reactions in the troposphere, which generate about 5 × 1012 kg of carbon monoxide per year. Other natural sources of CO include volcanoes, forest fires, and other forms of combustion. In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on heme from the breakdown of hemoglobin. This process produces a certain amount of carboxyhemoglobin in normal people, even if they do not inhale carbon monoxide. Since the first report that carbon monoxide was a normal neurotransmitter in 1993, as well as one of the three gases that naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has received much attention as a biological regulator. In many tissues, all three gases act as anti-inflammatory agents, vasodilators, and promoters of neovascular growth. Small amounts of carbon monoxide are being clinically tested as a drug. However, excessive amounts of carbon monoxide cause carbon monoxide poisoning.

Molecular Properties

Carbon monoxide has a molecular weight of 28.0, making it slightly lighter than air, which has an average molecular weight of 28.8. According to the ideal gas law, CO is therefore less dense than air. The bond length between the carbon atom and the oxygen atom is 112.8 pm. This bond length is consistent with a triple bond, as in molecular nitrogen (N2), which has a similar bond length and almost the same molecular weight. The carbon-oxygen double bonds are much longer, for example 120.8 m for formaldehyde. The boiling point (82 K) and melting point (68 K) are very similar to N2 (77 K and 63 K, respectively). The bond dissociation energy of 1072 kJ/mol is stronger than that of N2 (942 kJ/mol) and represents the strongest known chemical bond. The ground state of the carbon monoxide electron is singlet, as there are no unpaired electrons.

Bonding and dipole moment

Carbon and oxygen together have a total of 10 electrons in the valence shell. Following the octet rule for carbon and oxygen, two atoms form a triple bond, with six electrons in common in three bonding molecular orbitals, rather than the usual double bond found in organic carbonyl compounds. Since four of the shared electrons come from the oxygen atom and only two from the carbon, one bonding orbital is occupied by two electrons from the oxygen atoms, forming a dative or dipole bond. This results in a C ← O polarization of the molecule, with a small negative charge on carbon and a small positive charge on oxygen. The other two bonding orbitals each occupy one electron from carbon and one from oxygen, forming (polar) covalent bonds with reversed C → O polarization, since oxygen is more electronegative than carbon. In free carbon monoxide, the net negative charge δ- remains at the end of the carbon, and the molecule has a small dipole moment of 0.122 D. Thus, the molecule is asymmetric: oxygen has more electron density than carbon, and also a small positive charge, compared to carbon, which is negative. In contrast, the isoelectronic dinitrogen molecule does not have a dipole moment. If carbon monoxide acts as a ligand, the polarity of the dipole can reverse with a net negative charge at the oxygen end, depending on the structure of the coordination complex.

Bond polarity and oxidation state

Theoretical and experimental studies show that despite the greater electronegativity of oxygen, the dipole moment proceeds from the more negative end of carbon to the more positive end of oxygen. These three bonds are actually polar covalent bonds that are highly polarized. The calculated polarization to the oxygen atom is 71% for the σ bond and 77% for both π bonds. The oxidation state of carbon to carbon monoxide in each of these structures is +2. It is calculated as follows: all bonding electrons are considered to belong to more electronegative oxygen atoms. Only two non-bonding electrons on carbon are assigned to carbon. In this count, carbon has only two valence electrons in the molecule compared to four in a free atom.

Biological and physiological properties

Toxicity

Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. Carbon monoxide is a colorless substance, odorless and tasteless, but very toxic. It combines with hemoglobin to form carboxyhemoglobin, which "usurps" the site in hemoglobin that normally carries oxygen but is inefficient for delivering oxygen to body tissues. Concentrations as low as 667 ppm can cause up to 50% of the body's hemoglobin to be converted to carboxyhemoglobin. 50% carboxyhemoglobin levels can lead to convulsions, coma and death. In the United States, the Department of Labor limits long-term levels of carbon monoxide exposure in the workplace to 50 parts per million. For a short period of time, absorption of carbon monoxide is cumulative, as its half-life is about 5 hours in fresh air. The most common symptoms of carbon monoxide poisoning can be similar to other types of poisoning and infections, and include symptoms such as headache, nausea, vomiting, dizziness, fatigue and a feeling of weakness. Affected families often believe they are victims of food poisoning. Babies can be irritable and feed poorly. Neurological symptoms include confusion, disorientation, blurred vision, fainting (loss of consciousness), and seizures. Some descriptions of carbon monoxide poisoning include retinal hemorrhage as well as an abnormal cherry-red color to the blood. In most clinical diagnoses, these features are rare. One of the difficulties with the usefulness of this "cherry" effect is that it corrects, or masks, an otherwise unhealthy appearance, since the main effect of removing venous hemoglobin is to make the suffocated person appear more normal, or a dead person appears alive, similar to the effect of red dyes in embalming composition. This staining effect in anoxic CO-poisoned tissue is due to the commercial use of carbon monoxide in meat staining. Carbon monoxide also binds to other molecules such as myoglobin and mitochondrial cytochrome oxidase. Exposure to carbon monoxide can cause significant damage to the heart and central nervous system, especially in the globus pallidus, often associated with long-term chronic conditions. Carbon monoxide can have serious adverse effects on the fetus of a pregnant woman.

normal human physiology

Carbon monoxide is produced naturally in the human body as a signaling molecule. Thus, carbon monoxide may have a physiological role in the body as a neurotransmitter or blood vessel relaxant. Due to the role of carbon monoxide in the body, disturbances in its metabolism are associated with various diseases, including neurodegeneration, hypertension, heart failure and inflammation.

CO functions as an endogenous signaling molecule.

CO modulates the functions of the cardiovascular system

CO inhibits platelet aggregation and adhesion

CO may play a role as a potential therapeutic agent

Microbiology

Carbon monoxide is a nutrient for methanogenic archaea, a building block for acetyl coenzyme A. This is a topic for a new field of bioorganometallic chemistry. Extremophilic microorganisms can thus metabolize carbon monoxide in places such as the heat vents of volcanoes. In bacteria, carbon monoxide is produced by the reduction of carbon dioxide by the enzyme carbon monoxide dehydrogenase, a Fe-Ni-S-containing protein. CooA is a carbon monoxide receptor protein. The scope of its biological activity is still unknown. It may be part of the signaling pathway in bacteria and archaea. Its prevalence in mammals has not been established.

Prevalence

Carbon monoxide is found in various natural and man-made environments.

Carbon monoxide is present in small amounts in the atmosphere, mainly as a product of volcanic activity, but is also a product of natural and man-made fires (for example, forest fires, burning of plant residues, and burning sugar cane). The burning of fossil fuels also contributes to the formation of carbon monoxide. Carbon monoxide occurs in dissolved form in molten volcanic rocks at high pressures in the Earth's mantle. Because natural sources of carbon monoxide are variable, it is extremely difficult to accurately measure natural gas emissions. Carbon monoxide is a rapidly decaying greenhouse gas and also exerts indirect radiative forcing by increasing concentrations of methane and tropospheric ozone through chemical reactions with other atmospheric constituents (e.g. hydroxyl radical, OH) that would otherwise destroy them. As a result of natural processes in the atmosphere, it is eventually oxidized to carbon dioxide. Carbon monoxide is both short-lived in the atmosphere (lasting about two months on average) and has a spatially variable concentration. In the atmosphere of Venus, carbon monoxide is created by the photodissociation of carbon dioxide by electromagnetic radiation with a wavelength shorter than 169 nm. Because of its long viability in the middle troposphere, carbon monoxide is also used as a transport tracer for pollutant plumes.

Urban pollution

Carbon monoxide is a temporary atmospheric pollutant in some urban areas, mainly from the exhaust pipes of internal combustion engines (including vehicles, portable and standby generators, lawn mowers, washing machines, etc.) and from incomplete combustion various other fuels (including firewood, coal, charcoal, oil, wax, propane, natural gas, and garbage). Large CO pollution can be observed from space over cities.

Role in the formation of ground-level ozone

Carbon monoxide, along with aldehydes, is part of a series of chemical reaction cycles that form photochemical smog. It reacts with the hydroxyl radical (OH) to give the radical intermediate HOCO, which rapidly transfers the radical hydrogen O2 to form a peroxide radical (HO2) and carbon dioxide (CO2). The peroxide radical then reacts with nitric oxide (NO) to form nitrogen dioxide (NO2) and a hydroxyl radical. NO 2 gives O(3P) through photolysis, thereby forming O3 after reacting with O2. Since the hydroxyl radical is formed during the formation of NO2, the balance of the sequence of chemical reactions, starting with carbon monoxide, leads to the formation of ozone: CO + 2O2 + hν → CO2 + O3 (Where hν refers to the photon of light absorbed by the NO2 molecule in the sequence) Although the creation NO2 is an important step in producing low level ozone, it also increases the amount of ozone in another, somewhat mutually exclusive way, by reducing the amount of NO that is available to react with ozone.

indoor air pollution

In closed environments, the concentration of carbon monoxide can easily rise to lethal levels. On average, in the United States annually from non-automotive consumer goods producing carbon monoxide, 170 people die. However, according to the Florida Department of Health, "More than 500 Americans die each year from accidental exposure to carbon monoxide and thousands more in the US require emergency medical attention for non-fatal carbon monoxide poisoning." These products include faulty fuel combustion appliances such as stoves, cookers, water heaters, and gas and kerosene room heaters; mechanically driven equipment such as portable generators; fireplaces; and charcoal, which is burned in homes and other enclosed spaces. The American Association of Poison Control Centers (AAPCC) reported 15,769 cases of carbon monoxide poisoning, which resulted in 39 deaths in 2007. In 2005, CPSC reported 94 deaths related to carbon monoxide poisoning from a generator. Forty-seven of those deaths occurred during power outages due to severe weather, including Hurricane Katrina. However, people are dying from carbon monoxide poisoning from non-food items such as cars left running in garages attached to homes. The Centers for Disease Control and Prevention reports that every year, several thousand people go to the hospital emergency room for carbon monoxide poisoning.

Presence in the blood

Carbon monoxide is absorbed through breathing and enters the bloodstream through gas exchange in the lungs. It is also produced during the metabolism of hemoglobin and enters the blood from tissues, and thus is present in all normal tissues, even if it is not inhaled into the body. Normal levels of carbon monoxide circulating in the blood are between 0% and 3%, and are higher in smokers. Carbon monoxide levels cannot be assessed through a physical examination. Laboratory tests require a blood sample (arterial or venous) and a laboratory analysis for a CO-oximeter. In addition, non-invasive carboxyhemoglobin (SPCO) with pulsed CO oximetry is more effective than invasive methods.

Astrophysics

Outside the Earth, carbon monoxide is the second most abundant molecule in the interstellar medium, after molecular hydrogen. Due to its asymmetry, the carbon monoxide molecule produces much brighter spectral lines than the hydrogen molecule, making CO much easier to detect. Interstellar CO was first detected by radio telescopes in 1970. It is currently the most commonly used tracer of molecular gas in the interstellar medium of galaxies, and molecular hydrogen can only be detected using ultraviolet light, requiring space telescopes. Observations of carbon monoxide provide most of the information about the molecular clouds in which most stars form. Beta Pictoris, the second brightest star in the constellation Pictor, exhibits an excess of infrared radiation compared to normal stars of its type, due to the large amount of dust and gas (including carbon monoxide) near the star.

Production

Many methods have been developed to produce carbon monoxide.

industrial production

The main industrial source of CO is producer gas, a mixture containing mainly carbon monoxide and nitrogen, formed when carbon is burned in air at high temperature when there is an excess of carbon. In the oven, air is forced through a bed of coke. Initially produced CO2 is balanced with the remaining hot coal to produce CO. The reaction of CO2 with carbon to produce CO is described as the Boudouard reaction. Above 800°C, CO is the dominant product:

CO2 + C → 2 CO (ΔH = 170 kJ/mol)

Another source is "water gas", a mixture of hydrogen and carbon monoxide produced by an endothermic reaction of steam and carbon:

H2O + C → H2 + CO (ΔH = +131 kJ/mol)

Other similar "syngas" can be obtained from natural gas and other fuels. Carbon monoxide is also a by-product of the reduction of metal oxide ores with carbon:

MO + C → M + CO

Carbon monoxide is also produced by the direct oxidation of carbon in a limited amount of oxygen or air.

2C (s) + O 2 → 2CO (g)

Since CO is a gas, the reduction process can be controlled by heating using the positive (favorable) entropy of the reaction. The Ellingham diagram shows that CO production is preferred over CO2 at high temperatures.

Preparation in the laboratory

Carbon monoxide is conveniently obtained in the laboratory by dehydration of formic acid or oxalic acid e.g. with concentrated sulfuric acid. Another way is to heat a homogeneous mixture of powdered zinc metal and calcium carbonate, which releases CO and leaves zinc oxide and calcium oxide:

Zn + CaCO3 → ZnO + CaO + CO

Silver nitrate and iodoform also give carbon monoxide:

CHI3 + 3AgNO3 + H2O → 3HNO3 + CO + 3AgI

coordination chemistry

Most metals form coordination complexes containing covalently attached carbon monoxide. Only metals in lower oxidation states will combine with carbon monoxide ligands. This is because sufficient electron density is needed to facilitate reverse donation from the metallic DXZ orbital, to the π* molecular orbital from CO. The lone pair on the carbon atom in CO also donates electron density in dx²-y² on the metal to form a sigma bond. This electron donation is also manifested by the cis effect, or labilization of CO ligands in the cis position. Nickel carbonyl, for example, is formed by the direct combination of carbon monoxide and metallic nickel:

Ni + 4 CO → Ni(CO) 4 (1 bar, 55 °C)

For this reason, the nickel in the tube or part of it must not come into prolonged contact with carbon monoxide. Nickel carbonyl readily decomposes back to Ni and CO upon contact with hot surfaces, and this method is used for commercial nickel refining in the Mond process. In nickel carbonyl and other carbonyls, the electron pair on the carbon interacts with the metal; carbon monoxide donates an electron pair to the metal. In such situations, carbon monoxide is called a carbonyl ligand. One of the most important metal carbonyls is iron pentacarbonyl, Fe(CO)5. Many metal-CO complexes are made by decarbonylation of organic solvents rather than from CO. For example, iridium trichloride and triphenylphosphine react in refluxing 2-methoxyethanol or DMF to give IrCl(CO)(PPh3)2. Metal carbonyls in coordination chemistry are usually studied using infrared spectroscopy.

Organic chemistry and chemistry of the main groups of elements

In the presence strong acids and water, carbon monoxide reacts with alkenes to form carboxylic acids in a process known as the Koch-Haaf reaction. In the Guttermann-Koch reaction, arenes are converted to benzaldehyde derivatives in the presence of AlCl3 and HCl. Organolithium compounds (such as butyllithium) react with carbon monoxide, but these reactions have little scientific application. Although CO reacts with carbocations and carbanions, it is relatively unreactive with organic compounds without the intervention of metal catalysts. With reagents from the main group, CO undergoes several remarkable reactions. CO chlorination is an industrial process that produces the important phosgene compound. With borane, CO forms an adduct, H3BCO, which is isoelectronic with the acylium + cation. CO reacts with sodium to create products derived from the C-C bond. The compounds cyclohexahehexone or triquinoyl (C6O6) and cyclopentanepentone or leuconic acid (C5O5), which have so far only been obtained in trace amounts, can be regarded as polymers of carbon monoxide. At pressures above 5 GPa, carbon monoxide is converted into a solid polymer of carbon and oxygen. It is metastable at atmospheric pressure, but it is a powerful explosive.

Usage

Chemical industry

Carbon monoxide is an industrial gas that has many applications in the production of bulk chemical substances. Large amounts of aldehydes are obtained by the reaction of hydroformylation of alkenes, carbon monoxide and H2. Hydroformylation in the Shell process makes it possible to create detergent precursors. Phosgene, suitable for producing isocyanates, polycarbonates and polyurethanes, is produced by passing purified carbon monoxide and chlorine gas through a layer of porous activated carbon, which serves as a catalyst. World production of this compound in 1989 was estimated at 2.74 million tons.

CO + Cl2 → COCl2

Methanol is produced by the hydrogenation of carbon monoxide. In a related reaction, the hydrogenation of carbon monoxide involves the formation of a C-C bond, as in the Fischer-Tropsch process, where carbon monoxide is hydrogenated to liquid hydrocarbon fuels. This technology allows coal or biomass to be converted into diesel fuel. In the Monsanto process, carbon monoxide and methanol react in the presence of a rhodium-based catalyst and homogeneous hydroiodic acid to form acetic acid. This process is responsible for much of the industrial production of acetic acid. AT industrial scale, pure carbon monoxide is used to purify nickel in the Mond process.

meat coloring

Carbon monoxide is used in modified atmospheric packaging systems in the United States, mainly in fresh meat products such as beef, pork and fish, to maintain their fresh appearance. Carbon monoxide combines with myoglobin to form carboxymyoglobin, a bright cherry red pigment. Carboxymyoglobin is more stable than the oxidized form of myoglobin, oxymyoglobin, which can oxidize to the brown pigment metmyoglobin. This stable red color can last much longer than regular packaged meat. Typical carbon monoxide levels used in plants using this process are 0.4% to 0.5%. This technology was first recognized as "generally safe" (GRAS) by the US Food and Drug Administration (FDA) in 2002 for use as a secondary packaging system, and does not require labelling. In 2004, the FDA approved CO as the primary packaging method, stating that CO does not mask the smell of spoilage. Despite this ruling, it remains controversial whether this method masks food spoilage. In 2007, a bill was proposed in the US House of Representatives to call the modified carbon monoxide packaging process a color additive, but the bill was not passed. This packaging process is banned in many other countries, including Japan, Singapore, and countries in the European Union.

The medicine

In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on heme from the breakdown of hemoglobin. This process produces a certain amount of carboxyhemoglobin in normal people, even if they do not inhale carbon monoxide. Since the first report that carbon monoxide was a normal neurotransmitter in 1993, as well as one of three gases that naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has received a great deal of clinical attention as a biological regulator. . In many tissues, all three gases are known to act as anti-inflammatory agents, vasodilators, and neovascular growth enhancers. However, these issues are complex because neovascular growth is not always beneficial, as it plays a role in tumor growth as well as in the development of wet macular degeneration, a disease whose risk is increased 4 to 6-fold by smoking (a major source of carbon monoxide). in the blood, several times more than natural production). There is a theory that in some nerve cell synapses, when long-term memories are stored, the receiving cell produces carbon monoxide, which is passed back to the transmitting chamber, causing it to be transmitted more easily in the future. Some of these nerve cells have been shown to contain guanylate cyclase, an enzyme that is activated by carbon monoxide. Many laboratories around the world have conducted research involving carbon monoxide regarding its anti-inflammatory and cytoprotective properties. These properties can be used to prevent the development of a number of pathological conditions, including ischemic reperfusion injury, transplant rejection, atherosclerosis, severe sepsis, severe malaria, or autoimmune diseases. Human clinical trials have been conducted, but the results have not yet been released.

Everything that surrounds us consists of compounds of various chemical elements. We breathe not just air, but a complex organic compound containing oxygen, nitrogen, hydrogen, carbon dioxide and other necessary components. The influence of many of these elements on the human body in particular and on life on Earth in general has not yet been fully studied. In order to understand the processes of interaction of elements, gases, salts and other formations with each other, the subject "Chemistry" was introduced into the school course. Grade 8 is the start of chemistry lessons according to the approved general education program.

One of the most common compounds found in both earth's crust, and in the atmosphere, is an oxide. An oxide is a compound of any chemical element with an oxygen atom. Even the source of all life on Earth - water - is hydrogen oxide. But in this article we will not talk about oxides in general, but about one of the most common compounds - carbon monoxide. These compounds are obtained by the fusion of oxygen and carbon atoms. These compounds can contain various amounts of carbon and oxygen atoms, but two main compounds of carbon and oxygen should be distinguished: carbon monoxide and carbon dioxide.

Chemical formula and method for producing carbon monoxide

What is its formula? Carbon monoxide is pretty easy to remember - CO. The carbon monoxide molecule is formed by a triple bond, and therefore has a fairly high strength compounds and has a very small internuclear distance (0.1128 nm). The energy of rupture of this chemical compound is 1076 kJ/mol. The triple bond arises due to the fact that the element carbon has a p-orbital in its structure of the atom, not occupied by electrons. This circumstance creates an opportunity for the carbon atom to become an electron pair acceptor. And the oxygen atom, on the contrary, has an unshared pair of electrons on one of the p-orbitals, which means it has electron-donor capabilities. When these two atoms are combined, in addition to two covalent bonds, a third one also appears - a donor-acceptor covalent bond.

Exist various ways receiving CO. One of the simplest is passing carbon dioxide over hot coal. Under laboratory conditions, carbon monoxide is produced by the following reaction: formic acid is heated with sulfuric acid, which separates formic acid into water and carbon monoxide.

CO is also released when oxalic and sulfuric acids are heated.

Physical properties of CO

Carbon monoxide (2) has the following physical properties - it is a colorless gas that does not have a pronounced odor. All odors that appear when carbon monoxide leaks are decay products of organic impurities. It is much lighter than air, extremely toxic, very poorly soluble in water, and highly flammable.

The most important property of CO is its negative effect on the human body. Carbon monoxide poisoning can be fatal. More details about the effects of carbon monoxide on the human body will be discussed below.

Chemical properties of CO

Main chemical reactions, in which oxides of carbon (2) can be used - this is a redox reaction, as well as an addition reaction. The redox reaction is expressed in the ability of CO to restore metal from oxides by mixing them with further heating.

When interacting with oxygen, carbon dioxide is formed with the release of a significant amount of heat. Carbon monoxide burns with a bluish flame. A very important function of carbon monoxide is its interaction with metals. As a result of such reactions, metal carbonyls are formed, the vast majority of which are crystalline substances. They are used for the manufacture of ultra-pure metals, as well as for the application of metal coatings. By the way, carbonyls have proven themselves well as catalysts for chemical reactions.

Chemical formula and method for producing carbon dioxide

Carbon dioxide, or carbon dioxide, has the chemical formula CO 2 . The structure of the molecule is somewhat different from that of CO. In this formation, carbon has an oxidation state of +4. The structure of the molecule is linear, and therefore non-polar. The CO 2 molecule does not have the same strong strength as CO. The earth's atmosphere contains about 0.03% carbon dioxide by total volume. An increase in this indicator destroys the ozone layer of the Earth. In science, this phenomenon is called the greenhouse effect.

Carbon dioxide can be obtained in various ways. In industry, it is formed as a result of the combustion of flue gases. May be a by-product of the alcohol manufacturing process. It can be obtained in the process of decomposition of air into basic components, such as nitrogen, oxygen, argon and others. Under laboratory conditions, carbon monoxide (4) can be obtained in the process of burning limestone, and at home, carbon dioxide can be obtained using the reaction of citric acid and baking soda. By the way, this is how carbonated drinks were made at the very beginning of their production.

Physical properties of CO 2

Carbon dioxide is a colorless gaseous substance without a characteristic pungent odor. because of high number oxidation, this gas has a slightly sour taste. This product does not support the combustion process, as it is itself the result of combustion. With an increased concentration of carbon dioxide, a person loses the ability to breathe, which leads to death. More details about the effects of carbon dioxide on the human body will be discussed below. CO 2 is much heavier than air and highly soluble in water even at room temperature.

One of the most interesting properties carbon dioxide is that it does not have a liquid state of aggregation at normal atmospheric pressure. However, if the structure of carbon dioxide is affected by a temperature of -56.6 ° C and a pressure of about 519 kPa, then it transforms into a colorless liquid.

With a significant decrease in temperature, the gas is in the state of the so-called "dry ice" and evaporates at a temperature higher than -78 ° C.

Chemical properties of CO 2

According to its chemical properties, carbon monoxide (4), whose formula is CO 2 , is a typical acid oxide and has all its properties.

1. When interacting with water, it forms carbonic acid, which has low acidity and low stability in solutions.

2. When interacting with alkalis, carbon dioxide forms the corresponding salt and water.

3. During interaction with active metal oxides, it promotes the formation of salts.

4. Does not support the combustion process. Only some active metals, such as lithium, potassium, sodium, can activate this process.

The effect of carbon monoxide on the human body

Let's return to the main problem of all gases - the effect on the human body. Carbon monoxide belongs to the group of extremely life-threatening gases. For humans and animals, it is an extremely strong toxic substance that, when ingested, seriously affects the blood, nervous system of the body and muscles (including the heart).

Carbon monoxide in the air is impossible to recognize, as this gas does not have any pronounced odor. That is what makes him dangerous. Getting through the lungs into the human body, carbon monoxide activates its destructive activity in the blood and hundreds of times faster than oxygen begins to interact with hemoglobin. The result is a very stable compound called carboxyhemoglobin. It interferes with the delivery of oxygen from the lungs to the muscles, which leads to muscle starvation of tissues. The brain is particularly affected by this.

Due to the inability to recognize carbon monoxide poisoning through the sense of smell, you should be aware of some of the main signs that appear in the early stages:

• dizziness accompanied by headache;
• tinnitus and flickering before the eyes;
• strong heartbeat and shortness of breath;
• redness of the face.

In the future, the victim of poisoning develops severe weakness, sometimes vomiting. In severe cases of poisoning, involuntary convulsions are possible, accompanied by further loss of consciousness and coma. If the patient is not provided with appropriate health care, then death is possible.

The effect of carbon dioxide on the human body

Oxides of carbon with an acidity of +4 belong to the category of asphyxiating gases. In other words, carbon dioxide is not toxic substance, however, can significantly affect the flow of oxygen to the body. When the level of carbon dioxide rises to 3-4%, a person has a serious weakness, he begins to sleep. When the level rises to 10%, severe headaches, dizziness, hearing loss begin to develop, sometimes loss of consciousness is observed. If the concentration of carbon dioxide rises to a level of 20%, then death from oxygen starvation occurs.

The treatment for carbon dioxide poisoning is very simple - give the victim access to clean air, if necessary, give artificial respiration. In extreme cases, you need to connect the victim to a ventilator.

From the descriptions of the effect of these two carbon oxides on the body, we can conclude that carbon monoxide still poses a great danger to humans with its high toxicity and directed impact on the body from the inside.

Carbon dioxide does not differ in such insidiousness and is less harmful to humans, therefore it is this substance that people actively use even in the food industry.

The use of carbon oxides in industry and their impact on various aspects of life

Carbon oxides are widely used in various fields of human activity, and their spectrum is extremely rich. So, carbon monoxide is used with might and main in metallurgy in the process of iron smelting. CO has gained wide popularity as a material for keeping food refrigerated. This oxide is used to treat meat and fish to give them fresh look and not change the taste. It is important not to forget about the toxicity of this gas and remember that the allowable dose should not exceed 200 mg per 1 kg of product. CO in recent times are increasingly used in the automotive industry as a fuel for gas-powered vehicles.

Carbon dioxide is non-toxic, so its scope is widely introduced into the food industry, where it is used as a preservative or baking powder. CO 2 is also used in the manufacture of mineral and carbonated waters. In its solid state ("dry ice"), it is often used in freezers to keep a room or appliance at a consistently low temperature.

Carbon dioxide fire extinguishers have gained great popularity, the foam of which completely isolates the fire from oxygen and prevents the fire from flaring up. Accordingly, another area of ​​application - Fire safety. Cylinders in air pistols are also charged with carbon dioxide. And of course, almost every one of us has read what an air freshener for rooms consists of. Yes, one of the ingredients is carbon dioxide.

As you can see, due to its minimal toxicity, carbon dioxide is more and more common in Everyday life man, while carbon monoxide found use in heavy industry.

There are other carbon compounds with oxygen, since the formula of carbon and oxygen allows the use of various options for compounds with different amount carbon and oxygen atoms. A number of oxides can vary from C 2 O 2 to C 32 O 8 . And to describe each of them, it will take more than one page.

Oxides of carbon in nature

Both types of carbon oxides considered here are present in one way or another in the natural world. So, carbon monoxide can be a product of forest combustion or the result of human activity (exhaust gases and hazardous waste from industrial enterprises).

Carbon dioxide already known to us is also part of the complex composition of the air. Its content in it is about 0.03% of the total volume. With an increase in this indicator, the so-called "greenhouse effect" occurs, which modern scientists are so afraid of.

Carbon dioxide is emitted by animals and humans through exhalation. It is the main source of such an element useful for plants as carbon, which is why many scientists beat the storm, pointing out the inadmissibility of large-scale deforestation. If plants stop absorbing carbon dioxide, then the percentage of its content in the air can rise to critical indicators for human life.

Apparently, many people in power have forgotten the textbook material they studied in childhood. general chemistry. Grade 8”, otherwise the issue of deforestation in many parts of the world would be given more serious attention. By the way, this also applies to the problem of the presence of carbon monoxide in the environment. The amount of human waste and the percentage of releases of this extremely toxic material into the environment is increasing day by day. And it’s not a fact that the fate of the world, described in the wonderful cartoon “Wolly”, will not be repeated, when humanity had to leave the earth that was polluted to the ground and go to other worlds in search of a better life.

Oxides of carbon

In recent years, pedagogical science has given preference to personality-oriented learning. The formation of individual personality traits occurs in the process of activity: study, play, work. That's why an important factor learning is the organization of the learning process, the nature of the relationship between teachers and students and students among themselves. Based on these ideas, I am trying to build the educational process in a special way. At the same time, each student chooses his own pace of studying the material, has the opportunity to work at an accessible level, in a situation of success. At the lesson, it is possible to master and improve not only subject, but also such general educational skills and abilities as setting a learning goal, choosing means and ways to achieve it, monitoring one's achievements, correcting mistakes. Students learn to work with literature, draw up notes, diagrams, drawings, work in a group, in pairs, individually, conduct a constructive exchange of opinions, reason logically and draw conclusions.

It is not easy to conduct such lessons, but if you succeed, you feel satisfaction. I offer the scenario of one of my lessons. It was attended by colleagues, administration and a psychologist.

Lesson type. Learning new material.

Goals. Based on motivation and actualization basic knowledge and students' skills to consider the structure, physical and Chemical properties, production and use of carbon monoxide and carbon dioxide.

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Equipment and reagents.“Programmed Interrogation” cards, poster diagram, devices for obtaining gases, glasses, test tubes, fire extinguisher, matches; lime water, sodium oxide, chalk, hydrochloric acid, indicator solutions, H 2 SO 4 (conc.), HCOOH, Fe 2 O 3 .

Poster scheme
"The structure of the carbon monoxide molecule (carbon(II)) CO"

DURING THE CLASSES

Tables for students in the classroom are arranged in a circle. The teacher and students have the opportunity to freely move to the laboratory tables (1, 2, 3). For the lesson, children sit at study tables (4, 5, 6, 7, ...) with each other at will (free groups of 4 people).

Teacher. Wise Chinese proverb(written beautifully on the board) says:

"I hear - I forget,
I see - I remember
I do - I understand.

Do you agree with the conclusions of the Chinese sages?

And what Russian proverbs reflect Chinese wisdom?

Children give examples.

Teacher. Indeed, only by creating, creating, you can get a valuable product: new substances, devices, machines, as well as intangible values ​​- conclusions, generalizations, conclusions. I invite you today to take part in the study of the properties of two substances. It is known that during the technical inspection of the car, the driver provides a certificate on the state of the exhaust gases of the car. The concentration of what gas is indicated in the certificate?

(O t in e t. CO.)

Student. This gas is poisonous. Getting into the blood, it causes poisoning of the body (“burning out”, hence the name of the oxide - carbon monoxide). In life-threatening quantities, it is found in car exhaust gases.(reads a report from the newspaper that the driver, who fell asleep to death while the engine was running in the garage, died to death). The antidote for carbon monoxide poisoning is inhalation. fresh air and pure oxygen. The other carbon monoxide is carbon dioxide.

Teacher. There is a Programmed Poll card on your desks. Familiarize yourself with its contents and on a blank piece of paper mark the numbers of those tasks, the answers to which you know based on your life experience. Opposite the task-statement number, write the formula of carbon monoxide to which this statement refers.

Student consultants (2 people) collect answer sheets and, based on the results of the answers, form new groups for further work.

Programmed survey "Carbon oxides"

1. The molecule of this oxide consists of one carbon atom and one oxygen atom.

2. The bond between atoms in a molecule is covalent polar.

3. A gas that is practically insoluble in water.

4. This oxide molecule has one carbon atom and two oxygen atoms.

5. It has no odor or color.

6. A gas soluble in water.

7. Does not liquefy even at -190 °C ( t bp = –191.5 °С).

8. Acid oxide.

9. Easily compressed, at 20 °C under a pressure of 58.5 atm it becomes liquid, solidifies into "dry ice".

10. Not poisonous.

11. Non-salt forming.

12. combustible

13. Interacts with water.

14. Reacts with basic oxides.

15. Reacts with metal oxides, recovering free metals from them.

16. Obtained by the interaction of acids with salts of carbonic acid.

17. Poison.

18. Interacts with alkalis.

19. The source of carbon absorbed by plants in greenhouses and greenhouses leads to increased yields.

20. Used in the carbonation of water and drinks.

Teacher. Review the content of the card again. Group the information into 4 blocks:

structure,

physical properties,

Chemical properties,

receipt.

The teacher provides an opportunity to speak to each group of students, summarizes the speeches. Then students of different groups choose their work plan - the order of studying oxides. To this end, they number blocks of information and justify their choice. The order of study may be as written above, or with any other combination of the four blocks marked.

The teacher draws students' attention to the key points of the topic. Since carbon oxides are gaseous substances, they must be handled with care (safety regulations). The teacher approves the plan of each group and distributes consultants (pre-prepared students).

Demonstration experiments

1. Pouring carbon dioxide from glass to glass.

2. Extinguishing candles in a glass as CO 2 accumulates.

3. Drop a few small pieces of "dry ice" into a glass of water. The water will boil, and thick white smoke will pour out of it.

CO 2 gas is already liquefied at room temperature under a pressure of 6 MPa. In the liquid state, it is stored and transported in steel cylinders. If you open the valve of such a cylinder, then liquid CO 2 will begin to evaporate, due to which strong cooling occurs and part of the gas turns into a snow-like mass - “dry ice”, which is pressed and used to store ice cream.

4. Demonstration of a chemical foam fire extinguisher (OHP) and an explanation of the principle of its operation using a model - test tubes with a stopper and a gas outlet tube.

Information on structure at table number 1 (instruction cards 1 and 2, the structure of CO and CO 2 molecules).

Information about physical properties- at table number 2 (work with a textbook - Gabrielyan O.S. Chemistry-9. M.: Bustard, 2002, p. 134–135).

Data on the preparation and chemical properties- on tables No. 3 and 4 (instruction cards 3 and 4, instructions for conducting practical work, pp. 149–150 of the textbook).

Homework

The teacher suggests taking the "Programmed Poll" card home and, in preparation for the next lesson, consider ways to obtain information. (How did you know that the gas under study liquefies, reacts with acid, is poisonous, etc.?)

Independent work students

practical work groups of children perform at different speeds. Therefore, those who complete the work faster are offered games.

Fifth extra

Four substances can have something in common, and the fifth substance is out of line, superfluous.

1. Carbon, diamond, graphite, carbide, carbine. (Carbide.)

2. Anthracite, peat, coke, oil, glass. (Glass.)

3. Limestone, chalk, marble, malachite, calcite. (Malachite.)

4. Crystalline soda, marble, potash, caustic, malachite. (Caustic.)

5. Phosgene, phosphine, hydrocyanic acid, potassium cyanide, carbon disulfide. (Phosphine.)

6. Sea water, mineral water, distilled water, ground water, hard water. (Distilled water.)

7. milk of lime, fluff, slaked lime, limestone, lime water. (Limestone.)

8. Li 2 CO 3; (NH 4) 2 CO 3; CaCO 3 ; K 2 CO 3 , Na 2 CO 3 . (CaCO 3 .)

Synonyms

Write the chemical formulas of substances or their names.

1. Halogen - ... (Chlorine or bromine.)

2. Magnesite - ... (MgCO 3 .)

3. Urea - ... ( Urea H2NC(O)NH2.)

4. Potash - ... (K 2 CO 3 .)

5. Dry ice - ... (CO 2 .)

6. Hydrogen oxide - ... ( Water.)

7. Ammonia – … (10% aqueous ammonia solution.)

8. Salts of nitric acid - ... ( Nitrates- KNO 3 , Ca(NO 3) 2 , NaNO 3 .)

9. Natural gas - ... ( Methane CH 4 .)

Antonyms

Write chemical terms that are opposite in meaning to the suggested ones.

1. Oxidizer - ... ( Reducing agent.)

2. Electron donor - ... ( electron acceptor.)

3. Acid properties - ... ( Basic properties.)

4. Dissociation - ... ( Association.)

5. Adsorption - ... ( Desorption.)

6. Anode - ... ( Cathode.)

7. Anion - ... ( Cation.)

8. Metal - ... ( Non-metal.)

9. Starting substances - ... ( reaction products.)

Search for patterns

Establish a sign that unites the indicated substances and phenomena.

1. Diamond, carbine, graphite - ... ( Allotropic modifications of carbon.)

2. Glass, cement, brick - ... ( Construction Materials.)

3. Breathing, decay, volcanic eruption - ... ( Processes accompanied by the release of carbon dioxide.)

4. CO, CO 2, CH 4, SiH 4 - ... ( Compounds of elements of group IV.)

5. NaHCO 3, CaCO 3, CO 2, H 2 CO 3 - ... ( Oxygen compounds of carbon.)

Physical properties.

Carbon monoxide is a colorless and odorless gas, slightly soluble in water.

t pl. 205 °С,

t b.p. 191 °С

critical temperature =140°С

critical pressure = 35 atm.

The solubility of CO in water is about 1:40 by volume.

Chemical properties.

Under ordinary conditions, CO is inert; when heated - reducing agent; non-salt-forming oxide.

1) with oxygen

2C +2 O + O 2 \u003d 2C +4 O 2

2) with metal oxides

C +2 O + CuO \u003d Cu + C +4 O 2

3) with chlorine (in the light)

CO + Cl 2 --hn-> COCl 2 (phosgene)

4) reacts with alkali melts (under pressure)

CO + NaOH = HCOONa (sodium formate (sodium formate))

5) forms carbonyls with transition metals

Ni + 4CO \u003d t ° \u003d Ni (CO) 4

Fe + 5CO \u003d t ° \u003d Fe (CO) 5

Carbon monoxide does not chemically interact with water. CO also does not react with alkalis and acids. He is extremely venomous.

From the chemical side, carbon monoxide is characterized mainly by its tendency to addition reactions and its reducing properties. Both of these tendencies, however, usually appear only at elevated temperatures. Under these conditions, CO combines with oxygen, chlorine, sulfur, some metals, etc. At the same time, when heated, carbon monoxide reduces many oxides to metals, which is very important for metallurgy. Along with heating, an increase in the chemical activity of CO is often caused by its dissolution. Thus, in solution, it is able to reduce salts of Au, Pt, and some other elements to free metals already at ordinary temperatures.

At elevated temperatures and high pressures, CO interacts with water and caustic alkalis: in the first case, HCOOH is formed, and in the second, sodium formic acid. The last reaction proceeds at 120 °C, a pressure of 5 atm and finds technical use.

Easy reduction of palladium chloride in solution according to the summary scheme:

PdCl 2 + H 2 O + CO \u003d CO 2 + 2 HCl + Pd

serves as the most commonly used reaction for the discovery of carbon monoxide in a mixture of gases. Already very small amounts of CO are easily detected by the slight coloring of the solution due to the release of finely crushed palladium metal. The quantitative determination of CO is based on the reaction:

5 CO + I 2 O 5 \u003d 5 CO 2 + I 2.

Oxidation of CO in solution often proceeds at a noticeable rate only in the presence of a catalyst. When choosing the latter, the nature of the oxidizing agent plays the main role. So, KMnO 4 most rapidly oxidizes CO in the presence of finely divided silver, K 2 Cr 2 O 7 - in the presence of mercury salts, KClO 3 - in the presence of OsO 4. In general, in its reducing properties, CO is similar to molecular hydrogen, and its activity under normal conditions is higher than that of the latter. Interestingly, there are bacteria capable of obtaining the energy they need for life due to the oxidation of CO.

The comparative activity of CO and H 2 as reducing agents can be assessed by studying the reversible reaction:

H 2 O + CO \u003d CO 2 + H 2 + 42 kJ,

the equilibrium state of which at high temperatures is established rather quickly (especially in the presence of Fe 2 O 3). At 830 ° C, the equilibrium mixture contains equal amounts of CO and H 2, i.e., the affinity of both gases for oxygen is the same. Below 830 °C, CO is a stronger reducing agent, and higher, H 2 .

The binding of one of the products of the reaction discussed above, in accordance with the law of mass action, shifts its equilibrium. Therefore, by passing a mixture of carbon monoxide and water vapor over calcium oxide, hydrogen can be obtained according to the scheme:

H 2 O + CO + CaO \u003d CaCO 3 + H 2 + 217 kJ.

This reaction takes place already at 500 °C.

In air, CO ignites at about 700 ° C and burns with a blue flame to CO 2:

2 CO + O 2 \u003d 2 CO 2 + 564 kJ.

The significant heat release accompanying this reaction makes carbon monoxide a valuable gaseous fuel. However, it finds the widest application as a starting product for the synthesis of various organic substances.

The combustion of thick layers of coal in furnaces occurs in three stages:

1) C + O 2 \u003d CO 2; 2) CO 2 + C \u003d 2 CO; 3) 2 CO + O 2 \u003d 2 CO 2.

If the pipe is closed prematurely, a lack of oxygen is created in the furnace, which can cause the spread of CO throughout the heated room and lead to poisoning (burnout). It should be noted that the smell of "carbon monoxide" is not caused by CO, but by impurities of some organic substances.

A CO flame can have temperatures up to 2100°C. The combustion reaction of CO is interesting in that when heated to 700-1000 ° C, it proceeds at a noticeable rate only in the presence of traces of water vapor or other hydrogen-containing gases (NH 3 , H 2 S, etc.). This is due to the chain nature of the reaction under consideration, which proceeds through the intermediate formation of OH radicals according to the schemes:

H + O 2 \u003d HO + O, then O + CO \u003d CO 2, HO + CO \u003d CO 2 + H, etc.

At very high temperatures, the CO combustion reaction becomes markedly reversible. The content of CO 2 in an equilibrium mixture (at a pressure of 1 atm) above 4000 °C can only be negligible. The CO molecule itself is so thermally stable that it does not decompose even at 6000 °C. CO molecules have been found in the interstellar medium. Under the action of CO on metallic K at 80 ° C, a colorless crystalline, very explosive compound of the composition K 6 C 6 O 6 is formed. With the elimination of potassium, this substance easily passes into carbon monoxide C 6 O 6 ("triquinone"), which can be considered as a product of CO polymerization. Its structure corresponds to a six-membered cycle formed by carbon atoms, each of which is connected by a double bond to oxygen atoms.

The interaction of CO with sulfur according to the reaction:

CO + S = COS + 29 kJ

goes fast only at high temperatures. The resulting carbon thioxide (О=С=S) is a colorless and odorless gas (mp -139, bp -50 °С). Carbon monoxide (II) is able to combine directly with some metals. As a result, metal carbonyls are formed, which should be considered as complex compounds.

Carbon monoxide(II) also forms complex compounds with some salts. Some of them (OsCl 2 ·3CO, PtCl 2 ·CO, etc.) are stable only in solution. The formation of the latter substance is associated with the absorption of carbon monoxide (II) by a solution of CuCl in strong HCl. Similar compounds are apparently also formed in an ammonia solution of CuCl, which is often used to absorb CO in the analysis of gases.

Receipt.

Carbon monoxide is formed when carbon is burned in the absence of oxygen. Most often it is obtained as a result of the interaction of carbon dioxide with hot coal:

CO 2 + C + 171 kJ = 2 CO.

This reaction is reversible, and its equilibrium below 400 °C is almost completely shifted to the left, and above 1000 °C - to the right (Fig. 7). However, it is established with a noticeable speed only at high temperatures. Therefore, under normal conditions, CO is quite stable.

Rice. 7. Equilibrium CO 2 + C \u003d 2 CO.

The formation of CO from elements proceeds according to the equation:

2 C + O 2 \u003d 2 CO + 222 kJ.

Small amounts of CO are conveniently obtained by decomposition of formic acid: HCOOH \u003d H 2 O + CO

This reaction easily proceeds when HCOOH reacts with hot, strong sulfuric acid. In practice, this preparation is carried out either by the action of conc. sulfuric acid to liquid HCOOH (when heated), or by passing the vapors of the latter over phosphorus hemipentoxide. The interaction of HCOOH with chlorosulfonic acid according to the scheme:

HCOOH + CISO 3 H \u003d H 2 SO 4 + HCI + CO

goes on at normal temperatures.

A convenient method for laboratory production of CO can be heating with conc. sulfuric acid, oxalic acid or potassium iron cyanide. In the first case, the reaction proceeds according to the scheme: H 2 C 2 O 4 \u003d CO + CO 2 + H 2 O.

Along with CO, carbon dioxide is also released, which can be retained by passing the gas mixture through a barium hydroxide solution. In the second case, the only gaseous product is carbon monoxide:

K 4 + 6 H 2 SO 4 + 6 H 2 O \u003d 2 K 2 SO 4 + FeSO 4 + 3 (NH 4) 2 SO 4 + 6 CO.

Large amounts of CO can be obtained by incomplete combustion of coal in special furnaces - gas generators. Ordinary ("air") generator gas contains on average (vol.%): CO-25, N2-70, CO 2 -4 and small impurities of other gases. When burned, it gives 3300-4200 kJ per m 3. Replacing ordinary air with oxygen leads to a significant increase in CO content (and an increase in the calorific value of the gas).

Even more CO contains water gas, consisting (in the ideal case) of a mixture of equal volumes of CO and H 2 and giving 11700 kJ / m 3 during combustion. This gas is obtained by blowing water vapor through a layer of hot coal, and at about 1000 ° C, the interaction takes place according to the equation:

H 2 O + C + 130 kJ \u003d CO + H 2.

The reaction of formation of water gas proceeds with the absorption of heat, the coal is gradually cooled, and in order to maintain it in a hot state, it is necessary to alternate the passage of water vapor with the passage of air (or oxygen) into the gas generator. In this regard, water gas contains approximately CO-44, H 2 -45, CO 2 -5 and N 2 -6%. It is widely used for the synthesis of various organic compounds.

Often a mixed gas is obtained. The process of obtaining it is reduced to the simultaneous blowing of air and water vapor through a layer of hot coal, i.e. combining both methods described above. Therefore, the composition of the mixed gas is intermediate between generator and water. On average, it contains: CO-30, H 2 -15, CO 2 -5 and N 2 -50%. Cubic meter it gives when burned about 5400 kJ.