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 concentrations are above about 35 ppm, although it is also produced in normal animal metabolism in small amounts, and is believed 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. It 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.

History

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 maintain mechanical Vehicle 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 form 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 component. 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 springs COs 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 three gases that naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has gained great attention scientists 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 poisoning. carbon monoxide.

Molecular properties

Carbon monoxide has a molecular weight of 28.0, making it slightly lighter than air, whose average molecular mass is 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 reverse C → O polarization, since oxygen is more electronegative than carbon. In free carbon monoxide, the net negative charge δ- remains at the carbon end, 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 highly 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 feeling weak. 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 dead man seems 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, abnormalities 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 volcanic activity, but is also a product of natural and man-made fires (for example, forest fires, burning of crop residues, and burning of sugar cane). The burning of fossil fuels also contributes to the formation of carbon monoxide. Carbon monoxide is found in dissolved form in molten volcanic rocks during 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 leading to the formation of ozone low level, 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 enclosed environments, the concentration of carbon monoxide can easily rise to lethal levels. On average, 170 people die every year in the United States from non-automotive consumer products that produce carbon monoxide. 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 with 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 layer 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 favored 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, for example with concentrated sulfuric acid. Another way is to heat homogeneous mixture 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 of 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 towards 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 a metastable substance 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 bed 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. On an 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, primarily 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 conventional 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 debatable whether this method masks food spoilage. In 2007, a bill was proposed in the US House of Representatives to call the modified packaging process using carbon monoxide 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 synapses of nerve cells, 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.

Carbon forms two extremely stable oxides (CO and CO 2), three much less stable oxides (C 3 O 2 , C 5 O 2 and C 12 O 9), a number of unstable or poorly studied oxides (C 2 O, C 2 O 3 etc.) and non-stoichiometric graphite oxide. Among the listed oxides, CO and CO 2 play a special role.

DEFINITION

carbon monoxide under normal conditions, a combustible gas, colorless and odorless.

It is quite toxic due to its ability to form a complex with hemoglobin, which is about 300 times more stable than the oxygen-hemoglobin complex.

DEFINITION

Carbon dioxide under normal conditions, it is a colorless gas, about 1.5 times heavier than air, due to which it can be poured, like a liquid, from one vessel to another.

The mass of 1 liter of CO 2 under normal conditions is 1.98 g. The solubility of carbon dioxide in water is low: 1 volume of water at 20 o C dissolves 0.88 volumes of CO 2 , and at 0 o C - 1.7 volumes.

Direct oxidation of carbon with a lack of oxygen or air leads to the formation of CO, with a sufficient amount of them, CO 2 is formed. Some properties of these oxides are presented in table. one.

Table 1. Physical properties of carbon oxides.

Obtaining carbon monoxide

Pure CO can be obtained in the laboratory by dehydrating formic acid (HCOOH) with concentrated sulfuric acid at ~140°C:

HCOOH \u003d CO + H 2 O.

In small quantities, carbon dioxide can be easily obtained by the action of acids on carbonates:

CaCO 3 + 2HCl \u003d CaCl 2 + H 2 O + CO 2.

On an industrial scale, CO 2 is produced mainly as a by-product in the ammonia synthesis process:

CH 4 + 2H 2 O \u003d CO 2 + 4H 2;

CO + H 2 O \u003d CO 2 + H 2.

Large amounts of carbon dioxide are produced when limestone is burned:

CaCO 3 \u003d CaO + CO 2.

Chemical properties of carbon monoxide

Carbon monoxide is reactive at high temperatures. It manifests itself as a strong reducing agent. Reacts with oxygen, chlorine, sulfur, ammonia, alkalis, metals.

CO + NaOH = Na(HCOO) (t = 120 - 130 o C, p);

CO + H 2 \u003d CH 4 + H 2 O (t \u003d 150 - 200 o C, kat. Ni);

CO + 2H 2 \u003d CH 3 OH (t \u003d 250 - 300 o C, kat. CuO / Cr 2 O 3);

2CO + O 2 \u003d 2CO 2 (kat. MnO 2 / CuO);

CO + Cl 2 \u003d CCl 2 O (t \u003d 125 - 150 o C, cat. C);

4CO + Ni = (t = 50 - 100 o C);

5CO + Fe = (t = 100 - 200 o C, p).

Carbon dioxide exhibits acid properties: reacts with alkalis, ammonia hydrate. It is restored by active metals, hydrogen, carbon.

CO 2 + NaOH dilute = NaHCO 3 ;

CO 2 + 2NaOH conc \u003d Na 2 CO 3 + H 2 O;

CO 2 + Ba(OH) 2 = BaCO 3 + H 2 O;

CO 2 + BaCO 3 + H 2 O \u003d Ba (HCO 3) 2;

CO 2 + NH 3 × H 2 O \u003d NH 4 HCO 3;

CO 2 + 4H 2 \u003d CH 4 + 2H 2 O (t \u003d 200 o C, kat. Cu 2 O);

CO 2 + C \u003d 2CO (t\u003e 1000 o C);

CO 2 + 2Mg \u003d C + 2MgO;

2CO 2 + 5Ca = CaC 2 + 4CaO (t = 500 o C);

2CO 2 + 2Na 2 O 2 \u003d 2Na 2 CO 3 + O 2.

Application of carbon monoxide

Carbon monoxide is widely used as a fuel in the form of producer gas or water gas, and is also formed during the separation of many metals from their oxides by reduction with coal. Generator gas is obtained by passing air through hot coal. It contains about 25% CO, 4% CO2 and 70% N 2 with traces of H 2 and CH 4 62.

The use of carbon dioxide is most often due to its physical properties. It is used as a cooling agent, for carbonating beverages, for producing lightweight (foamed) plastics, and as a gas for creating an inert atmosphere.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

The task	Determine how many times heavier than air is carbon monoxide (IV)CO 2.
Solution	The ratio of the mass of a given gas to the mass of another gas taken in the same volume, at the same temperature and the same pressure, is called the relative density of the first gas over the second. This value shows how many times the first gas is heavier or lighter than the second gas. The relative molecular weight of air is taken equal to 29 (taking into account the content of nitrogen, oxygen and other gases in the air). It should be noted that the concept of "relative molecular weight of air" is used conditionally, since air is a mixture of gases. D air (CO 2) \u003d M r (CO 2) / M r (air); D air (CO 2) \u003d 44 / 29 \u003d 1.517. M r (CO 2) \u003d A r (C) + 2 × A r (O) \u003d 12 + 2 × 16 \u003d 12 + 32 \u003d 44.
Answer	Carbon monoxide (IV)CO 2 is 1.517 times heavier than air.

Carbon monoxide, also known as carbon monoxide, has a very strong molecular composition, is chemically inert, and does not dissolve well in water. This compound is also incredibly toxic; when it enters the respiratory system, it combines with blood hemoglobin, and it stops carrying oxygen to tissues and organs.

Chemical names and formula

Carbon monoxide is also known by other names, including carbon monoxide II. In everyday life, it is commonly referred to as carbon monoxide. This carbon monoxide is a poisonous, colorless, tasteless and odorless gas. His chemical formula- CO, and the mass of one molecule is 28.01 g/mol.

Impact on the body

Carbon monoxide combines with hemoglobin to form carboxyhemoglobin, which has no bandwidth oxygen. Inhalation of its vapors causes CNS (central nervous system) damage and suffocation. The resulting lack of oxygen causes headache, dizziness, decreased heart rate and respiratory rate, leading to fainting and subsequent death of the body.

Toxic gas

Carbon monoxide is produced by the partial combustion of substances containing carbon, for example in internal combustion engines. The compound contains 1 carbon atom covalently bonded to 1 oxygen atom. Carbon monoxide is highly toxic and is one of the most common causes of fatal poisoning worldwide. Exposure may cause damage to the heart and other organs.

What are the benefits of carbon monoxide?

Despite its serious toxicity, carbon monoxide is extremely useful - thanks to modern technologies, a number of vital products are created from it. Carbon monoxide, although today considered a pollutant, has always been present in nature, but not in such quantities as, for example, carbon dioxide.

Those who believe that the compound carbon monoxide does not exist in nature are mistaken. CO dissolves in molten volcanic rock at high pressures in the earth's mantle. The content of carbon oxides in volcanic gases varies from less than 0.01% to 2%, depending on the volcano. Since the natural of this compound is not a constant value, it is not possible to accurately measure natural gas emissions.

Chemical properties

Carbon monoxide (formula CO) refers to non-salt-forming or indifferent oxides. However, at a temperature of +200 o With it reacts with sodium hydroxide. During this chemical process, sodium formate is formed:

NaOH + CO = HCOONa (formic acid salt).

The properties of carbon monoxide are based on its reducing ability. Carbon monoxide:

Molecule structure

The two atoms that make up the carbon monoxide (CO) molecule are linked by a triple bond. Two of them are formed by the fusion of p-electrons of carbon atoms with oxygen, and the third is due to a special mechanism due to the free 2p orbital of carbon and the 2p electron pair of oxygen. This structure provides the molecule with high strength.

A bit of history

More Aristotle from ancient greece described the toxic fumes produced. The mechanism of death itself was not known. However, one of the ancient methods of execution was locking the offender in a steam room, where there were smoldering coals. The Greek physician Galen suggested that certain changes occur in the composition of the air that cause harm when inhaled.

During World War II, carbon monoxide-laced gas was used as fuel for motor vehicles in parts of the world where gasoline and diesel were scarce. External (with a few exceptions) charcoal or wood gas generators were installed, and a mixture of atmospheric nitrogen, carbon monoxide and a small amount of other gases was fed into a gas mixer. It was the so-called wood gas.

Oxidation of carbon monoxide

Carbon monoxide is formed during the partial oxidation of carbon-containing compounds. CO is formed when there is not enough oxygen to produce carbon dioxide (CO 2 ), such as when a furnace or internal combustion engine is operated in an enclosed space. If oxygen is present, as well as certain other atmospheric concentrations, carbon monoxide burns, emitting blue light, producing carbon dioxide, known as carbon dioxide.

Coal gas, widely used until the 1960s for indoor lighting, cooking and heating, had CO as the predominant fuel component. Some processes in modern technologies, such as iron smelting, still produce carbon monoxide as a by-product. The CO compound itself is oxidized to CO 2 at room temperature.

Does CO exist in nature?

Does carbon monoxide exist in nature? One of its natural sources is photochemical reactions occurring in the troposphere. These processes are expected to be able to generate about 5×10 12 kg of substance e annually. Among other sources, as mentioned above, are volcanoes, forest fires and other

Molecular properties

Carbon monoxide has a molar mass of 28.0, making it slightly less dense than air. The bond length between two atoms is 112.8 micrometers. It's close enough that it provides one of the strongest chemical bonds. Both elements in a CO compound together have about 10 electrons in one valence shell.

As a rule, a double bond occurs in organic carbonyl compounds. A characteristic CO is that a strong triple bond arises between atoms with 6 common electrons in 3 bonded molecular orbitals. Since 4 of the shared electrons come from the oxygen atom and only 2 from carbon, one bonded orbital is occupied by two electrons from O 2 , forming a dative or dipole bond. This causes a C ← O polarization of the molecule with a small "-" charge on carbon and a small "+" charge on oxygen.

The remaining two bound orbitals occupy one charged particle from carbon and one from oxygen. The molecule is asymmetric: oxygen has a higher electron density than carbon and is also slightly positively charged compared to negative carbon.

Receipt

In industry, carbon monoxide CO is obtained by heating carbon dioxide or water vapor with coal without access to air:

CO 2 + C \u003d 2CO;

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

The last resulting mixture is also called water or synthesis gas. IN laboratory conditions carbon monoxide II by acting on organic acids with concentrated sulfuric acid, which acts as a dehydrating agent:

HCOOH \u003d CO + H 2 O;

H 2 C 2 O 4 \u003d CO 2 + H 2 O.

The main symptoms and help for CO poisoning

Does carbon monoxide cause poisoning? Yes, and very strong. is the most common occurrence worldwide. The most common symptoms:

• feeling of weakness;
• nausea;
• dizziness;
• fatigue;
• irritability;
• poor appetite;
• headache;
• disorientation;
• visual impairment;
• vomit;
• fainting;
• convulsions.

Exposure to this toxic gas can cause significant damage, which can often lead to long-term chronic conditions. Carbon monoxide can cause serious damage to a pregnant woman's fetus. Victims, for example, after a fire, should be given immediate assistance. it is urgent to call an ambulance, give access to fresh air, remove clothing that restricts breathing, calm, warm. Severe poisoning, as a rule, is treated only under the supervision of doctors, in a hospital.

Application

Carbon monoxide, as already mentioned, is poisonous and dangerous, but it is one of the basic compounds that are used in modern industry for organic synthesis. CO is used to produce pure metals, carbonyls, phosgene, carbon sulphide, methyl alcohol, formamide, and aromatic acids. This substance is also used as fuel. Despite its toxicity and poisonousness, it is often used as a raw material for the production of various substances in the chemical industry.

Carbon Monoxide vs Carbon Dioxide: What's the Difference?

Carbon monoxide and carbon dioxide (CO and CO 2) are often mistaken for each other. Both gases are odorless and colorless, and both negatively affect the cardiovascular system. Both gases can enter the body through inhalation, skin and eyes. These compounds, when exposed to a living organism, have a number of common symptoms - headaches, dizziness, convulsions and hallucinations. Most people have a hard time telling the difference and don't realize that car exhaust emits both CO and CO 2 . Indoors, an increase in the concentration of these gases can be hazardous to the health and safety of the person exposed to them. What is the difference?

At high concentrations, both can be fatal. The difference is that CO 2 is a common natural gas required for all plant and animal life. CO is not common. It is a by-product of oxygen-free fuel combustion. The critical chemical difference is that CO 2 contains one carbon atom and two oxygen atoms, while CO has only one. Carbon dioxide is non-flammable, while monoxide is more likely to ignite.

Carbon dioxide naturally occurs in the atmosphere: humans and animals breathe in oxygen and exhale carbon dioxide, which means that living beings can withstand small amounts of it. This gas is also necessary for the implementation of photosynthesis by plants. However, carbon monoxide does not occur naturally in the atmosphere and can cause health problems even at low concentrations. The density of both gases is also different. Carbon dioxide is heavier and denser than air, while carbon monoxide is slightly lighter. This feature of them should be taken into account when installing appropriate sensors in houses.

The physical properties of carbon monoxide (carbon monoxide CO) at normal atmospheric pressure are considered depending on the temperature at its negative and positive values.

In tables the following physical properties of CO are presented: carbon monoxide density ρ , specific heat capacity at constant pressure Cp, thermal conductivity coefficients λ and dynamic viscosity μ .

The first table shows the density and specific heat of carbon monoxide CO in the temperature range from -73 to 2727°C.

The second table gives the values ​​of such physical properties of carbon monoxide as thermal conductivity and its dynamic viscosity in the temperature range from minus 200 to 1000°C.

The density of carbon monoxide, as well as, depends significantly on temperature - when carbon monoxide CO is heated, its density decreases. For example, at room temperature, the density of carbon monoxide is 1.129 kg / m 3, but in the process of heating to a temperature of 1000 ° C, the density of this gas decreases by 4.2 times - to a value of 0.268 kg / m 3.

Under normal conditions (temperature 0°C) carbon monoxide has a density of 1.25 kg/m 3 . If we compare its density with or other common gases, then the density of carbon monoxide relative to air is less important - carbon monoxide is lighter than air. It is also lighter than argon, but heavier than nitrogen, hydrogen, helium and other light gases.

The specific heat capacity of carbon monoxide under normal conditions is 1040 J/(kg deg). As the temperature of this gas rises, its specific heat capacity increases. For example, at 2727°C its value is 1329 J/(kg deg).

Density of carbon monoxide CO and its specific heat capacity

t, °С	ρ, kg / m 3	C p , J/(kg deg)	t, °С	ρ, kg / m 3	C p , J/(kg deg)	t, °С	ρ, kg / m 3	C p , J/(kg deg)
-73	1,689	1045	157	0,783	1053	1227	0,224	1258
-53	1,534	1044	200	0,723	1058	1327	0,21	1267
-33	1,406	1043	257	0,635	1071	1427	0,198	1275
-13	1,297	1043	300	0,596	1080	1527	0,187	1283
-3	1,249	1043	357	0,535	1095	1627	0,177	1289
0	1,25	1040	400	0,508	1106	1727	0,168	1295
7	1,204	1042	457	0,461	1122	1827	0,16	1299
17	1,162	1043	500	0,442	1132	1927	0,153	1304
27	1,123	1043	577	0,396	1152	2027	0,147	1308
37	1,087	1043	627	0,374	1164	2127	0,14	1312
47	1,053	1043	677	0,354	1175	2227	0,134	1315
57	1,021	1044	727	0,337	1185	2327	0,129	1319
67	0,991	1044	827	0,306	1204	2427	0,125	1322
77	0,952	1045	927	0,281	1221	2527	0,12	1324
87	0,936	1045	1027	0,259	1235	2627	0,116	1327
100	0,916	1045	1127	0,241	1247	2727	0,112	1329

The thermal conductivity of carbon monoxide under normal conditions is 0.02326 W/(m deg). It increases with its temperature and at 1000°C becomes equal to 0.0806 W/(m deg). It should be noted that the thermal conductivity of carbon monoxide is slightly less than this value y.

The dynamic viscosity of carbon monoxide at room temperature is 0.0246·10 -7 Pa·s. When carbon monoxide is heated, its viscosity increases. Such a character of the dependence of dynamic viscosity on temperature is observed in . It should be noted that carbon monoxide is more viscous than water vapor and carbon dioxide CO 2 , but has a lower viscosity than nitric oxide NO and air.

Carbon monoxide, or carbon monoxide (CO) is a colorless, odorless and tasteless gas. It burns with a blue flame like hydrogen. Because of this, chemists confused it with hydrogen in 1776 when they first made carbon monoxide by heating zinc oxide with carbon. The molecule of this gas has a strong triple bond, like the nitrogen molecule. That is why there is some similarity between them: the melting and boiling points are almost the same. The carbon monoxide molecule has a high ionization potential.

Oxidized, carbon monoxide forms carbon dioxide. This reaction releases a large number of thermal energy. That is why carbon monoxide is used in heating systems.

carbon monoxide at low temperatures almost does not react with other substances, in the case of high temperatures the situation is different. The reactions of addition of various organic substances pass very quickly. A mixture of CO and oxygen in certain proportions is very dangerous because of the possibility of its explosion.

Obtaining carbon monoxide

Under laboratory conditions, carbon monoxide is produced by decomposition. It occurs under the influence of hot concentrated sulfuric acid, or when it is passed through phosphorus oxide. Another way is that a mixture of formic and oxalic acids is heated to a certain temperature. The liberated CO can be removed from this mixture by passing it through barite water ( saturated solution ).

The danger of carbon monoxide

Carbon monoxide is extremely dangerous to humans. It causes severe poisoning, often can cause death. The thing is that carbon monoxide has the ability to react with blood hemoglobin, which carries oxygen to all cells of the body. As a result of this reaction, carbohemoglobin is formed. Due to the lack of oxygen, the cells experience starvation.

The following symptoms of poisoning can be distinguished: nausea, vomiting, headache, loss of color perception, respiratory distress, and others. A person who has been poisoned by carbon monoxide needs first aid as soon as possible. First, you need to pull it out into fresh air and put a cotton swab dipped in ammonia to your nose. Next, rub the chest of the victim and apply heating pads to his legs. Plentiful warm drink is recommended. It is necessary to immediately after the discovery of symptoms to call a doctor.