The structure of carbon monoxide and carbon dioxide. This insidious carbon monoxide. How to determine carbon monoxide indoors

Carbon monoxide, carbon monoxide (CO), is a colorless, odorless, tasteless gas that is slightly less dense than air. It is toxic to hemoglobin-producing animals (including humans) at concentrations above about 35 ppm, although it is also produced in small quantities by normal animal metabolism 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 consists 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, nitrosonium cation, and molecular nitrogen. In coordination complexes, the carbon monoxide ligand is called a 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 - locking the criminal in a bathroom with smoldering coals. However, at that time the mechanism of death was unclear. The Greek physician Galen (129-199 AD) suggested that there was a change in the composition of the air, which caused harm to humans if inhaled. In 1776, French chemist de Lassonne 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 Scottish chemist William Cumberland Cruikshank in 1800. Its toxicity in dogs was thoroughly studied by Claude Bernard around 1846. During World War II, a gas mixture including carbon monoxide was used to power motorized vehicles operating in some parts of the world where gasoline and diesel fuel were scarce. External (with some exceptions) charcoal or wood-derived gasifiers were installed and a mixture of atmospheric nitrogen, carbon monoxide and small quantities of other gasification gases was introduced into 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 of the German Nazi death camps, most obviously 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 is formed when there is not enough oxygen to form carbon dioxide (CO2), such as when operating a stove or internal combustion engine, in a confined 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 heme 2 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 first reporting that carbon monoxide is 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 much scientific attention as a biological regulator In many tissues, all three gases act as anti-inflammatory agents, vasodilators, and promoters of neovascular growth. Clinical trials of small amounts of carbon monoxide as a drug are ongoing. 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, whose average molecular weight is 28.8. According to the ideal gas law, CO therefore has a lower density than air. The bond length between a carbon atom and an 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. 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 chemical bond known. The ground electron state of carbon monoxide is singlet, since there are no unpaired electrons.

Bonding and dipole moment

Carbon and oxygen together have a total of 10 electrons in their valence shell. Following the octet rule for carbon and oxygen, the two atoms form a triple bond, with six shared electrons in the 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 slight negative charge on the carbon and a slight positive charge on the 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 end of the carbon, and the molecule has a small dipole moment of 0.122 D. Thus, the molecule is asymmetric: oxygen has a higher electron density than carbon, as well as a small positive charge compared to carbon, which is negative. In contrast, the isoelectronic dinitrogen molecule has no dipole moment. If carbon monoxide acts as a ligand, the polarity of the dipole can change 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 comes 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. By this calculation, 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, odorless, tasteless substance, but very toxic. It combines with hemoglobin to produce carboxyhemoglobin, which "usurps" a site in hemoglobin that normally carries oxygen but is ineffective at delivering oxygen to the body's tissues. Concentrations as low as 667 ppm can cause up to 50% of the body's hemoglobin to be converted to carboxyhemoglobin. A carboxyhemoglobin level of 50% can lead to seizures, coma and death. In the United States, the Department of Labor limits long-term workplace exposure levels to carbon monoxide to 50 parts per million. Over a short period of time, carbon monoxide absorption 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 that they are victims of food poisoning. Babies may be irritable and eat poorly. Neurological symptoms include confusion, disorientation, blurred vision, syncope (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 signs are rarely observed. One of the difficulties associated 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 that the strangled person appears more normal, or a dead person appears alive, similar to the effect of red dyes in embalming composition. This dyeing effect in oxygen-free CO-poisoned tissue is associated with the commercial use of carbon monoxide in dyeing meat. 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 a pregnant woman's fetus.

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 a 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 cardiovascular functions

CO inhibits platelet aggregation and adhesion

CO may have a role as a potential therapeutic agent

Microbiology

Carbon monoxide is the breeding ground for methanogenic archaea, the building block for acetyl coenzyme A. This is a topic for the new field of bioorganometallic chemistry. Extremophile microorganisms can thus metabolize carbon monoxide in places such as thermal 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 a signaling pathway in bacteria and archaea. Its prevalence in mammals has not been established.

Prevalence

Carbon monoxide occurs in a variety of natural and artificial environments.

Carbon monoxide is present in small quantities 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 crop residues, and burning of sugar cane). Burning fossil fuels also contributes to the formation of carbon monoxide. Carbon monoxide occurs dissolved 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 emissions of the gas. Carbon monoxide is a rapidly decaying greenhouse gas and also exerts an indirect radiative effect by increasing the concentrations of methane and tropospheric ozone through chemical reactions with other atmospheric components (eg hydroxyl radical, OH) that would otherwise destroy them. Through natural processes in the atmosphere, it is eventually oxidized to carbon dioxide. Carbon monoxide is both short-lived in the atmosphere (lasting on average about two months) 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 wavelengths shorter than 169 nm. Because of its long viability in the mid-troposphere, carbon monoxide is also used as a transport tracer for plumes of harmful substances.

Urban pollution

Carbon monoxide is a temporary air pollutant in some urban areas, primarily from the exhaust pipes of internal combustion engines (including vehicles, portable and standby generators, lawn mowers, power washers, etc.) and from incomplete combustion various other fuels (including wood, coal, charcoal, petroleum, paraffin, 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 a hydroxyl radical (OH) to produce the radical intermediate HOCO, which quickly transfers radical hydrogen to O2 to form the peroxide radical (HO2) and carbon dioxide (CO2). The peroxide radical then reacts with nitric oxide (NO) to form nitrogen dioxide (NO2) and the hydroxyl radical. NO 2 produces O(3P) through photolysis, thereby forming O3 after reaction 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 results in 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 creation NO2 is an important step leading to the formation of 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, carbon monoxide concentrations can easily increase to lethal levels. On average, 170 people die each 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 United States require emergency medical treatment for nonfatal carbon monoxide poisoning.” These products include defective fuel combustion appliances such as furnaces, ranges, 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 indoor spaces. The American Association of Poison Control Centers (AAPCC) reported 15,769 cases of carbon monoxide poisoning resulting in 39 deaths in 2007. In 2005, the CPSC reported 94 deaths related to carbon monoxide poisoning from a generator. Forty-seven of these deaths occurred during power outages due to severe weather, including Hurricane Katrina. However, people are dying from carbon monoxide poisoning produced by non-food products such as cars left running in garages attached to their homes. The Centers for Disease Control and Prevention reports that several thousand people go to the emergency room each year for carbon monoxide poisoning.

Presence in blood

Carbon monoxide is absorbed through respiration 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 is thus present in all normal tissues, even if it is not taken into the body through respiration. Normal levels of carbon monoxide circulating in the blood range from 0% to 3%, and are higher in smokers. Carbon monoxide levels cannot be assessed through a physical examination. Laboratory testing requires a blood sample (arterial or venous) and a laboratory CO-oximeter test. In addition, noninvasive carboxyhemoglobin (SPCO) with pulsed CO oximetry is more effective than invasive methods.

Astrophysics

Outside of Earth, carbon monoxide is the second most abundant molecule in the interstellar medium, after molecular hydrogen. Because of 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 discovered using radio telescopes in 1970. It is currently the most commonly used indicator 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 emission 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 generator gas, a mixture containing mainly carbon monoxide and nitrogen produced when carbon is burned in air at high temperatures when there is excess carbon. In the oven, air is passed through a bed of coke. The initially produced CO2 is balanced with the remaining hot coal to produce CO2. The reaction of CO2 with carbon to produce CO is described as the Boudoir reaction. At temperatures above 800°C, CO is the predominant product:

CO2 + C → 2 CO (ΔH = 170 kJ/mol)

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

H2O + C → H2 + CO (ΔH = +131 kJ/mol)

Other similar "syngases" can be produced from natural gas and other fuels. Carbon monoxide is also a byproduct of the reduction of metal oxide ores with carbon:

MO + C → M + CO

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

2C (s) + O 2 → 2СО (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 the formation of CO is favored over CO2 at high temperatures.

Preparation in the laboratory

Carbon monoxide is conveniently obtained in the laboratory by dehydrating formic acid or oxalic acid, for example, using concentrated sulfuric acid. Another method is to heat a homogeneous mixture of powdered zinc metal and calcium carbonate, which releases CO and leaves behind zinc oxide and calcium oxide:

Zn + CaCO3 → ZnO + CaO + CO

Silver nitrate and iodoform also produce 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 the reverse donation from the metal 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 the labilization of CO ligands in the cis position. Nickel carbonyl, for example, is formed by the direct combination of carbon monoxide and nickel metal:

Ni + 4 CO → Ni (CO) 4 (1 bar, 55 °C)

For this reason, nickel in the tube or part thereof should not come into prolonged contact with carbon monoxide. Nickel carbonyl readily decomposes back to Ni and CO when in contact with hot surfaces, and this method is used for the industrial purification of nickel 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 prepared by decarbonylation of organic solvents rather than from CO. For example, iridium trichloride and triphenylphosphine react in boiling 2-methoxyethanol or DMF to produce IrCl(CO)(PPh3)2. Metal carbonyls in coordination chemistry are usually studied using infrared spectroscopy.

Organic chemistry and chemistry of 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 Koch-Haaf reactions. 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 reactants from the main group, CO undergoes several notable reactions. Chlorination of CO is an industrial process that results in the formation of the important compound phosgene. 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 cyclohexahegexone or triquinoyl (C6O6) and cyclopentanepentone or leuconic acid (C5O5), which have hitherto been obtained only in trace amounts, can be considered as polymers of carbon monoxide. At pressures greater than 5 GPa, carbon monoxide turns into a solid polymer of carbon and oxygen. It is metastable at atmospheric pressure, but is a powerful explosive.

Usage

Chemical industry

Carbon monoxide is an industrial gas that has many uses in the production of bulk chemicals. Large quantities of aldehydes are produced by the hydroformylation reaction of alkenes, carbon monoxide and H2. Hydroformylation in the Shell process makes it possible to create detergent precursors. Phosgene, useful for the production of 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 hydrogenation of carbon monoxide. In a related reaction, 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 the conversion of coal or biomass into diesel fuel. In the Monsanto process, carbon monoxide and methanol react in the presence of a rhodium catalyst and homogeneous hydroiodic acid to form acetic acid. This process is responsible for most 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 atmosphere packaging systems in the US, primarily in the packaging of 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 between 0.4% and 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 labeling. In 2004, the FDA approved CO as a primary packaging method, stating that CO does not mask spoilage odors. 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 a modified carbon monoxide packaging process a color additive, but the bill failed to pass. This packaging process is banned in many other countries, including Japan, Singapore and the European Union.

Medicine

In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and heme 2 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 first reporting that carbon monoxide is 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 much clinical attention as a biological regulator. . In many tissues, all three gases are known to act as anti-inflammatory agents, vasodilators, and promoters of neovascular growth. 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 for which the risk increases 4 to 6 times with smoking (a major source of carbon monoxide). in the blood, several times more than natural production). There is a theory that at some nerve cell synapses, when long-term memories are stored, the receiving cell produces carbon monoxide, which is passed back to the sending chamber, causing it to be transmitted more easily in the future. Some such 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. Clinical trials have been conducted in humans, 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. 8th grade is the start of chemistry lessons according to the approved general education program.

One of the most common compounds found both in the earth's crust and in the atmosphere is 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 merging oxygen and carbon atoms. These compounds can contain varying amounts of carbon and oxygen atoms, but there are two main compounds of carbon and oxygen: carbon monoxide and carbon dioxide.

Chemical formula and method of producing carbon monoxide

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

There are various ways to produce CO. One of the simplest is passing carbon dioxide over hot coal. In the laboratory, carbon monoxide is produced using the following reaction: formic acid is heated with sulfuric acid, which separates the formic acid into water and carbon monoxide.

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

Physical properties of CO

Carbon monoxide (2) has the following physical properties - it is a colorless gas with no pronounced odor. All foreign odors that appear during a carbon monoxide leak are products of the breakdown 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. The effects of carbon monoxide on the human body will be discussed in more detail below.

Chemical properties of CO

The main chemical reactions in which carbon oxides (2) can be used are redox reactions and addition reactions. The redox reaction is expressed in the ability of CO to reduce metal from oxides by mixing them with further heating.

When interacting with oxygen, carbon dioxide is formed and a significant amount of heat is released. 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 production of ultra-pure metals, as well as for applying metal coating. By the way, carbonyls have proven themselves well as catalysts for chemical reactions.

Chemical formula and method of producing carbon dioxide

Carbon dioxide, or carbon dioxide, has the chemical formula CO 2 . The structure of the molecule is slightly different from that of CO. In this formation, carbon has an oxidation state of +4. The structure of the molecule is linear, which means it is non-polar. The CO 2 molecule is not as strong as CO. The earth's atmosphere contains about 0.03% carbon dioxide by total volume. An increase in this indicator destroys the Earth's ozone layer. 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 combustion of flue gases. May be a by-product of the alcohol production process. It can be obtained through the process of decomposing air into its main components, such as nitrogen, oxygen, argon and others. In laboratory conditions, carbon monoxide (4) can be obtained by burning limestone, and at home, carbon dioxide can be produced using the reaction of citric acid and baking soda. By the way, this is exactly 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. Due to the high oxidation number, this gas has a slightly sour taste. This product does not support the combustion process, since it is itself the result of combustion. With increased concentrations of carbon dioxide, a person loses the ability to breathe, which leads to death. The effects of carbon dioxide on the human body will be discussed in more detail below. CO 2 is much heavier than air and is highly soluble in water even at room temperature.

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

When the temperature drops significantly, the gas is in the state of so-called “dry ice” and evaporates at a temperature higher than -78 o C.

Chemical properties of CO 2

In terms of its chemical properties, carbon monoxide (4), whose formula is CO 2, is a typical acidic oxide and has all its properties.

1. When interacting with water, carbonic acid is formed, which has weak 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 certain active metals, such as lithium, potassium, and 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, which, when ingested, seriously affects the blood, nervous system of the body and muscles (including the heart).

Carbon monoxide in the air cannot be recognized, since this gas does not have any distinct odor. This is precisely why he is dangerous. Entering the human body through the lungs, carbon monoxide activates its destructive activity in the blood and begins to interact with hemoglobin hundreds of times faster than oxygen. As a result, a very stable compound called carboxyhemoglobin appears. It interferes with the delivery of oxygen from the lungs to the muscles, which leads to muscle tissue starvation. The brain is especially seriously affected by this.

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

• dizziness accompanied by headache;
• ringing in the ears and flickering before the eyes;
• palpitations and shortness of breath;
• facial redness.

Subsequently, 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 medical care in a timely manner, death is possible.

The effect of carbon dioxide on the human body

Carbon oxides with acidity +4 belong to the category of asphyxiating gases. In other words, carbon dioxide is not a toxic substance, but it can significantly affect the flow of oxygen to the body. When the level of carbon dioxide increases to 3-4%, a person becomes seriously weak and begins to feel drowsy. When the level increases to 10%, severe headaches, dizziness, hearing loss begin to develop, and sometimes loss of consciousness occurs. If the concentration of carbon dioxide rises to a level of 20%, then death occurs from oxygen starvation.

Treatment for carbon dioxide poisoning is very simple - give the victim access to clean air and, if necessary, perform artificial respiration. As a last resort, you need to connect the victim to a ventilator.

From the descriptions of the influence 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 targeted effect on the body from the inside.

Carbon dioxide is not so insidious and is less harmful to humans, which is why people actively use this substance even in the food industry.

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

Carbon oxides have a very wide application in various fields of human activity, and their spectrum is extremely rich. Thus, carbon monoxide is widely used in metallurgy in the process of smelting cast iron. CO has gained wide popularity as a material for refrigerated food storage. This oxide is used to process meat and fish to give them a fresh look and not change the taste. It is important not to forget about the toxicity of this gas and remember that the permissible dose should not exceed 200 mg per 1 kg of product. CO has recently been increasingly used in the automotive industry as a fuel for gas vehicles.

Carbon dioxide is non-toxic, so its scope of application is widespread in the food industry, where it is used as a preservative or leavening agent. CO 2 is also used in the production of mineral and carbonated waters. In its solid form (“dry ice”), it is often used in freezers to maintain a consistently low temperature in a room or appliance.

Carbon dioxide fire extinguishers have become very popular, the foam of which completely isolates the fire from oxygen and prevents the fire from flaring up. Accordingly, another area of ​​application is fire safety. The cylinders in air pistols are also charged with carbon dioxide. And of course, almost every one of us has read what a room air freshener consists of. Yes, one of the components is carbon dioxide.

As we can see, due to its minimal toxicity, carbon dioxide is more and more common in human everyday life, while carbon monoxide has found application in heavy industry.

There are other carbon compounds with oxygen; fortunately, the formula of carbon and oxygen allows the use of various variants of compounds with different numbers of 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.

Carbon oxides in nature

Both types of carbon oxides discussed here are present in the natural world in one way or another. Thus, 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, which we already know, is also part of the complex composition of air. Its content in it is about 0.03% of the total volume. When this indicator increases, the so-called “greenhouse effect” arises, which modern scientists fear so much.

Carbon dioxide is released by animals and humans through exhalation. It is the main source of such an element as carbon, which is useful for plants, which is why many scientists are firing on all cylinders, pointing out the unacceptability of large-scale deforestation. If plants stop absorbing carbon dioxide, then the percentage of its content in the air may increase to critical levels for human life.

Apparently, many people in power have forgotten the material they covered in the textbook “General Chemistry. 8th grade”, otherwise the issue of deforestation in many parts of the world would be given more serious attention. This, by the way, also applies to the problem of carbon monoxide in the environment. The amount of human waste and the percentage of emissions of this unusually toxic material into the environment is growing day by day. And it’s not a fact that the fate of the world described in the wonderful cartoon “Wally” will not repeat itself, when humanity had to leave the Earth, which had been polluted to its foundations, and go to other worlds in search of a better life.

Physical properties.

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

t pl. 205 °C,

t kip. 191 °C

critical temperature =140°C

critical pressure = 35 atm.

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

Chemical properties.

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

1) with oxygen

2C +2 O + O 2 = 2C +4 O 2

2) with metal oxides

C +2 O + CuO = 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 formic acid (sodium formate))

5) forms carbonyls with transition metals

Ni + 4CO =t°= Ni(CO) 4

Fe + 5CO =t°= Fe(CO) 5

Carbon monoxide does not react chemically with water. CO also does not react with alkalis and acids. It is extremely poisonous.

From the chemical side, carbon monoxide is characterized mainly by its tendency to undergo addition reactions and its reducing properties. However, both of these trends usually appear only at elevated temperatures. Under these conditions, CO combines with oxygen, chlorine, sulfur, some metals, etc. At the same time, carbon monoxide, when heated, 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 capable of reducing 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 latter reaction occurs at 120 °C, a pressure of 5 atm and is used technically.

The reduction of palladium chloride in solution is easy according to the general scheme:

PdCl 2 + H 2 O + CO = CO 2 + 2 HCl + Pd

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

5 CO + I 2 O 5 = 5 CO 2 + I 2.

The oxidation of CO in solution often occurs at a noticeable rate only in the presence of a catalyst. When selecting the latter, the main role is played by the nature of the oxidizing agent. Thus, KMnO 4 oxidizes CO most quickly in the presence of finely crushed 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 that, through the oxidation of CO, obtain the energy they need for life.

The comparative activity of CO and H2 as reducing agents can be assessed by studying the reversible reaction:

H 2 O + CO = CO 2 + H 2 + 42 kJ,

the equilibrium state of which at high temperatures is established quite 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, the stronger reducing agent is CO, above - H2.

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 = CaCO 3 + H 2 + 217 kJ.

This reaction occurs 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 = 2 CO 2 + 564 kJ.

The significant release of heat that accompanies this reaction makes carbon monoxide a valuable gaseous fuel. However, it is most widely used 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 = CO 2; 2) CO 2 + C = 2 CO; 3) 2 CO + O 2 = 2 CO 2.

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

The CO flame can have a temperature of up to 2100 °C. The CO combustion reaction is interesting in that when heated to 700-1000 °C, it proceeds at a noticeable speed 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 occurs through the intermediate formation of OH radicals according to the following schemes:

H + O 2 = HO + O, then O + CO = CO 2, HO + CO = CO 2 + H, etc.

At very high temperatures, the CO combustion reaction becomes noticeably reversible. The CO 2 content in an equilibrium mixture (under a pressure of 1 atm) above 4000 °C can only be negligibly small. The CO molecule itself is so thermally stable that it does not decompose even at 6000 °C. CO molecules have been discovered in the interstellar medium. When CO acts on metal K at 80 °C, a colorless crystalline, highly explosive compound of the composition K 6 C 6 O 6 is formed. With the elimination of potassium, this substance easily turns 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.

Interaction of CO with sulfur according to the reaction:

CO + S = COS + 29 kJ

It goes fast only at high temperatures. The resulting carbon thioxide (O=C=S) is a colorless and odorless gas (mp -139, bp -50 °C). Carbon (II) monoxide is capable of combining directly with certain metals. As a result, metal carbonyls are formed, which should be considered as complex compounds.

Carbon(II) monoxide 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 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 burns 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 noticeable speed only at high temperatures. Therefore, under normal conditions, CO is quite stable.

Rice. 7. Equilibrium CO 2 + C = 2 CO.

The formation of CO from elements follows the equation:

2 C + O 2 = 2 CO + 222 kJ.

It is convenient to obtain small amounts of CO by the decomposition of formic acid: HCOOH = H 2 O + CO

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

HCOOH + CISO 3 H = H 2 SO 4 + HCI + CO

It already works at normal temperatures.

A convenient method for laboratory production of CO can be heating with conc. sulfuric acid, oxalic acid or potassium iron sulfide. In the first case, the reaction proceeds according to the following scheme: H 2 C 2 O 4 = 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 solution of barium hydroxide. In the second case, the only gaseous product is carbon monoxide:

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

Large quantities of CO can be obtained by incomplete combustion of coal in special furnaces - gas generators. Conventional (“air”) generator gas contains on average (volume %): CO-25, N2-70, CO 2 -4 and small impurities of other gases. When burned, it produces 3300-4200 kJ per m3. 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 is contained in water gas, which consists (in an ideal case) of a mixture of equal volumes of CO and H 2 and produces 11,700 kJ/m 3 upon 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 = CO + H 2.

The reaction of the formation of water gas occurs with the absorption of heat, the coal gradually cools and 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.

Mixed gas is often obtained. The process of obtaining it boils down to simultaneously blowing air and water vapor through a layer of hot coal, i.e. a combination of 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%. A cubic meter of it produces about 5400 kJ when burned.

Content

Signs that carbon monoxide (carbon monoxide (II), carbon monoxide, carbon monoxide) has formed in the air in a dangerous concentration are difficult to determine - invisible, may not smell, accumulates in the room gradually, imperceptibly. It is extremely dangerous for human life: it is highly toxic; excessive levels in the lungs lead to severe poisoning and death. A high mortality rate from gas poisoning is recorded annually. The threat of poisoning can be reduced by following simple rules and using special carbon dioxide detectors.

What is carbon monoxide

Natural gas is formed during the combustion of any biomass; in industry, it is a product of the combustion of any carbon-based compounds. In both cases, a prerequisite for the release of gas is a lack of oxygen. Large volumes of it enter the atmosphere as a result of forest fires, in the form of exhaust gases generated during the combustion of fuel in car engines. For industrial purposes it is used in the production of organic alcohol, sugar, processing of animal meat and fish. A small amount of monoxide is also produced by human cells.

Properties

From a chemical point of view, monoxide is an inorganic compound with a single oxygen atom in the molecule, the chemical formula is CO. This is a chemical substance that has no characteristic color, taste or smell, it is lighter than air, but heavier than hydrogen, and is inactive at room temperatures. A person who smells only feels the presence of organic impurities in the air. It belongs to the category of toxic products; death at a concentration in the air of 0.1% occurs within one hour. The maximum permissible concentration characteristic is 20 mg/cub.m.

Effect of carbon monoxide on the human body

Carbon monoxide is deadly to humans. Its toxic effect is explained by the formation of carboxyhemoglobin in blood cells, a product of the addition of carbon monoxide (II) to blood hemoglobin. A high level of carboxyhemoglobin causes oxygen starvation, insufficient oxygen supply to the brain and other tissues of the body. With mild intoxication, its content in the blood is low; natural destruction is possible within 4-6 hours. At high concentrations, only medications are effective.

Carbon monoxide poisoning

Carbon monoxide is one of the most dangerous substances. In case of poisoning, intoxication of the body occurs, accompanied by a deterioration in the general condition of the person. It is very important to recognize the signs of carbon monoxide poisoning early. The result of treatment depends on the level of the substance in the body and how quickly help arrives. In this case, minutes count - the victim can either be completely cured, or remain sick forever (it all depends on the speed of response of the rescuers).

Symptoms

Depending on the degree of poisoning, headaches, dizziness, tinnitus, rapid heartbeat, nausea, shortness of breath, flickering in the eyes, and general weakness may occur. Drowsiness is often observed, which is especially dangerous when a person is in a gas-filled room. When a large amount of toxic substances enters the respiratory system, convulsions, loss of consciousness, and in especially severe cases, coma are observed.

First aid for carbon monoxide poisoning

The victim should be provided with first aid on the spot in case of carbon monoxide poisoning. You must immediately move him to fresh air and call a doctor. You should also remember about your safety: when entering a room with a source of this substance, you should only take a deep breath, and do not breathe inside. Until the doctor arrives, it is necessary to facilitate the access of oxygen to the lungs: unbutton buttons, remove or loosen clothes. If the victim loses consciousness and stops breathing, artificial ventilation is necessary.

Antidote for poisoning

A special antidote (antidote) for carbon monoxide poisoning is a medication that actively prevents the formation of carboxyhemoglobin. The action of the antidote leads to a decrease in the body's need for oxygen, supporting organs sensitive to lack of oxygen: the brain, liver, etc. It is administered intramuscularly in a dosage of 1 ml immediately after removing the patient from an area with a high concentration of toxic substances. The antidote can be re-administered no earlier than an hour after the first administration. Its use for prevention is allowed.

Treatment

In case of mild exposure to carbon monoxide, treatment is carried out on an outpatient basis; in severe cases, the patient is hospitalized. Already in the ambulance he is given an oxygen bag or mask. In severe cases, in order to give the body a large dose of oxygen, the patient is placed in a pressure chamber. An antidote is administered intramuscularly. Blood gas levels are constantly monitored. Further rehabilitation is medicinal, the actions of doctors are aimed at restoring the functioning of the brain, cardiovascular system, and lungs.

Consequences

Exposure to carbon monoxide on the body can cause serious illnesses: brain performance, behavior, and consciousness of a person change, and unexplained headaches appear. Memory, the part of the brain that is responsible for the transition of short-term memory to long-term memory, is especially susceptible to the influence of harmful substances. The patient may feel the effects of carbon monoxide poisoning only after several weeks. Most victims recover fully after a period of rehabilitation, but some suffer the consequences for the rest of their lives.

How to determine carbon monoxide indoors

Carbon monoxide poisoning is easy at home, and it doesn't just happen during a fire. The concentration of carbon dioxide is formed due to careless handling of the stove damper, during the operation of a faulty gas water heater or ventilation. The source of carbon monoxide may be a gas stove. If there is smoke in the room, this is already a reason to sound the alarm. There are special sensors for constant monitoring of gas levels. They monitor the gas concentration level and report if the norm is exceeded. The presence of such a device reduces the risk of poisoning.

Video

Attention! The information presented in the article is for informational purposes only. The materials in the article do not encourage self-treatment. Only a qualified doctor can make a diagnosis and make recommendations for treatment based on the individual characteristics of a particular patient.

MPC O.u. in the air of the working area – 20 mg/m3; couples; 4th hazard class (GN 2.2.5.686–98); CAS.

OU. – the main air pollutant in residential premises, a fire hazard. Particularly high concentrations of CO are observed in residential premises with stove heating using solid fuel if the rules for operating the stoves are violated. To prevent the formation and penetration of CO into the view valve, you can close it completely only when the firewood is completely burned out, the coals begin to darken and blue lights no longer appear above them. If the stove is fired with coal, then to prevent the formation of CO, the end of the firebox is done as follows: after making sure that the walls of the stove have warmed up sufficiently, completely clean the firebox of fuel residues, and then close the view valve. The remaining fuel is burned during the next fire. Children living in homes with gas stoves showed a decrease in lung capacity and an increase in respiratory diseases compared to children living in homes with electric stoves. If it is not possible to replace a gas stove with an electric one, then, at the very least, it is necessary to carefully monitor the serviceability of the burners on the stove, properly regulate air access, do not turn on the gas stove at full power, and it is advisable to avoid placing large pots and pans low on the burner. But in any case, it is necessary to use kitchen air purifiers. : CO filter gas masks, self-rescuers SPI-20, PDU-3, etc.