colorless gas Thermal Properties Melting temperature -205°C Boiling temperature -191.5°C Enthalpy (st. arb.) −110.52 kJ/mol Chemical properties Solubility in water 0.0026 g/100 ml Classification CAS number

• UN hazard class 2.3
• UN secondary hazard 2.1

The structure of the molecule

The CO molecule, like the isoelectronic nitrogen molecule, has a triple bond. Since these molecules are similar in structure, their properties are also similar - very low melting and boiling points, close values ​​of standard entropies, etc.

Within the framework of the method of valence bonds, the structure of the CO molecule can be described by the formula: C≡O:, and the third bond is formed according to the donor-acceptor mechanism, where carbon is an electron pair acceptor, and oxygen is a donor.

Due to the presence of a triple bond, the CO molecule is very strong (the dissociation energy is 1069 kJ / mol, or 256 kcal / mol, which is more than that of any other diatomic molecules) and has a small internuclear distance (d C≡O = 0.1128 nm or 1, 13Å).

The molecule is weakly polarized, the electric moment of its dipole μ = 0.04·10 -29 C·m (direction of the dipole moment O - →C +). Ionization potential 14.0 V, force coupling constant k = 18.6.

Discovery history

Carbon monoxide was first produced by the French chemist Jacques de Lasson when zinc oxide was heated with coal, but was initially mistaken for hydrogen because it burned with a blue flame. The fact that this gas contains carbon and oxygen was discovered by the English chemist William Cruikshank. Carbon monoxide outside the Earth's atmosphere was first discovered by the Belgian scientist M. Mizhot (M. Migeotte) in 1949 by the presence of the main vibrational-rotational band in the IR spectrum of the Sun.

Carbon monoxide in the Earth's atmosphere

There are natural and anthropogenic sources of entry into the Earth's atmosphere. Under natural conditions, on the Earth's surface, CO is formed during the incomplete anaerobic decomposition of organic compounds and during the combustion of biomass, mainly during forest and steppe fires. Carbon monoxide is formed in the soil both biologically (excreted by living organisms) and non-biologically. The release of carbon monoxide due to phenolic compounds common in soils containing OCH 3 or OH groups in ortho- or para-positions with respect to the first hydroxyl group has been experimentally proven.

The overall balance of production of non-biological CO and its oxidation by microorganisms depends on specific environmental conditions, primarily on humidity and the value of . For example, from arid soils, carbon monoxide is released directly into the atmosphere, thus creating local maxima in the concentration of this gas.

In the atmosphere, CO is the product of chain reactions involving methane and other hydrocarbons (primarily isoprene).

The main anthropogenic source of CO is currently the exhaust gases of internal combustion engines. Carbon monoxide is formed when hydrocarbon fuels are burned in internal combustion engines at insufficient temperatures or a poorly tuned air supply system (insufficient oxygen is supplied to oxidize CO to CO 2 ). In the past, a significant proportion of anthropogenic CO emissions into the atmosphere came from lighting gas used for indoor lighting in the 19th century. In composition, it approximately corresponded to water gas, that is, it contained up to 45% carbon monoxide. At present, in the municipal sector, this gas has been replaced by much less toxic natural gas (lower representatives of the homologous series of alkanes - propane, etc.)

The intake of CO from natural and anthropogenic sources is approximately the same.

Carbon monoxide in the atmosphere is in a rapid cycle: the average residence time is about 0.1 year, oxidized by hydroxyl to carbon dioxide.

Receipt

industrial way

2C + O 2 → 2CO (the thermal effect of this reaction is 22 kJ),

2. or when reducing carbon dioxide with hot coal:

CO 2 + C ↔ 2CO (ΔH=172 kJ, ΔS=176 J/K).

This reaction often occurs in the furnace furnace, when the furnace damper is closed too early (until the coals have completely burned out). The resulting carbon monoxide, due to its toxicity, causes physiological disorders ("burnout") and even death (see below), hence one of the trivial names - "carbon monoxide". The picture of the reactions taking place in the furnace is shown in the diagram.

The carbon dioxide reduction reaction is reversible, the effect of temperature on the equilibrium state of this reaction is shown in the graph. The flow of the reaction to the right provides the entropy factor, and to the left - the enthalpy factor. At temperatures below 400°C, the equilibrium is almost completely shifted to the left, and at temperatures above 1000°C to the right (in the direction of CO formation). At low temperatures, the rate of this reaction is very slow, so carbon monoxide is quite stable under normal conditions. This equilibrium has a special name boudoir balance.

3. Mixtures of carbon monoxide with other substances are obtained by passing air, water vapor, etc. through a layer of hot coke, hard or brown coal, etc. (see producer gas, water gas, mixed gas, synthesis gas).

laboratory method

TLV (maximum threshold concentration, USA): 25 MPC r.z. according to Hygienic Standards GN 2.2.5.1313-03 is 20 mg/m³

Protection against carbon monoxide

Due to such a good calorific value, CO is a component of various technical gas mixtures (see, for example, producer gas) used, among other things, for heating.

halogens. The reaction with chlorine has received the greatest practical application:

CO + Cl 2 → COCl 2

The reaction is exothermic, its thermal effect is 113 kJ, in the presence of a catalyst (activated carbon) it proceeds already at room temperature. As a result of the reaction, phosgene is formed - a substance that has become widespread in various branches of chemistry (and also as a chemical warfare agent). By analogous reactions, COF 2 (carbonyl fluoride) and COBr 2 (carbonyl bromide) can be obtained. Carbonyl iodide was not received. The exothermicity of reactions decreases rapidly from F to I (for reactions with F 2, the thermal effect is 481 kJ, with Br 2 - 4 kJ). It is also possible to obtain mixed derivatives, such as COFCl (for details, see halogen derivatives of carbonic acid).

By the reaction of CO with F 2 , in addition to carbonyl fluoride, a peroxide compound (FCO) 2 O 2 can be obtained. Its characteristics: melting point -42°C, boiling point +16°C, has a characteristic odor (similar to the smell of ozone), decomposes with an explosion when heated above 200°C (reaction products CO 2 , O 2 and COF 2), in acidic medium reacts with potassium iodide according to the equation:

(FCO) 2 O 2 + 2KI → 2KF + I 2 + 2CO 2

Carbon monoxide reacts with chalcogens. With sulfur it forms carbon sulfide COS, the reaction proceeds when heated, according to the equation:

CO + S → COS ΔG° 298 = −229 kJ, ΔS° 298 = −134 J/K

Similar selenoxide COSe and telluroxide COTe have also been obtained.

Restores SO 2:

SO 2 + 2CO → 2CO 2 + S

With transition metals, it forms very volatile, combustible and toxic compounds - carbonyls, such as Cr (CO) 6, Ni (CO) 4, Mn 2 CO 10, Co 2 (CO) 9, etc.

As stated above, carbon monoxide is slightly soluble in water, but does not react with it. Also, it does not react with solutions of alkalis and acids. However, it reacts with alkali melts:

CO + KOH → HCOOK

An interesting reaction is the reaction of carbon monoxide with metallic potassium in an ammonia solution. In this case, the explosive compound potassium dioxodicarbonate is formed:

2K + 2CO → K + O - -C 2 -O - K +

By reacting with ammonia at high temperatures, an important industrial compound, HCN, can be obtained. The reaction proceeds in the presence of a catalyst (oxide

−110.52 kJ/mol Steam pressure 35 ± 1 atm Chemical properties Solubility in water 0.0026 g/100 ml Classification Reg. CAS number 630-08-0 PubChem Reg. EINECS number 211-128-3 SMILES InChI Reg. EC number 006-001-00-2 RTECS FG3500000 CHEBI UN number 1016 ChemSpider Security Toxicity NFPA 704 Data is based on standard conditions (25 °C, 100 kPa) unless otherwise noted.

Carbon monoxide (carbon monoxide, carbon monoxide, carbon(II) oxide) is a colorless, extremely toxic, tasteless and odorless gas, lighter than air (under normal conditions). The chemical formula is CO.

The structure of the molecule

Due to the presence of a triple bond, the CO molecule is very strong (the dissociation energy is 1069 kJ / mol, or 256 kcal / mol, which is more than that of any other diatomic molecules) and has a small internuclear distance ( d C≡O = 0.1128 nm or 1.13 Å).

The molecule is weakly polarized, its electric dipole moment μ = 0.04⋅10 −29 C m . Numerous studies have shown that the negative charge in the CO molecule is concentrated on the carbon atom C − ←O + (the direction of the dipole moment in the molecule is opposite to that previously assumed). Ionization energy 14.0 eV, force coupling constant k = 18,6 .

Properties

Carbon monoxide(II) is a colorless, odorless and tasteless gas. combustible The so-called "carbon monoxide smell" is actually the smell of organic impurities.

Properties of carbon monoxide (II)

Standard Gibbs energy of formation Δ G	−137.14 kJ/mol (g) (at 298 K)
Standard Entropy of Education S	197.54 J/mol K (g) (at 298 K)
Standard molar heat capacity Cp	29.11 J/mol K (g) (at 298 K)
Enthalpy of melting Δ H pl	0.838 kJ/mol
Boiling enthalpy Δ H kip	6.04 kJ/mol
Critical temperature t Crete	-140.23°C
critical pressure P Crete	3.499 MPa
Critical density ρ crit	0.301 g/cm³

The main types of chemical reactions in which carbon monoxide (II) is involved are addition reactions and redox reactions, in which it exhibits reducing properties.

At room temperature, CO is inactive, its chemical activity increases significantly when heated and in solutions. So, in solutions, it restores salts,, and others to metals already at room temperature. When heated, it also reduces other metals, for example CO + CuO → Cu + CO 2. This is widely used in pyrometallurgy. The method for the qualitative detection of CO is based on the reaction of CO in solution with palladium chloride, see below.

Oxidation of CO in solution often proceeds at a noticeable rate only in the presence of a catalyst. When choosing the latter, the nature of the oxidizing agent plays the main role. So, KMnO 4 most rapidly oxidizes CO in the presence of finely divided silver, K 2 Cr 2 O 7 - in the presence of salts, KClO 3 - in the presence of OsO 4. In general, CO is similar in its reducing properties to molecular hydrogen.

Below 830 °C, CO is a stronger reducing agent, and higher, hydrogen. So the equilibrium of the reaction

H 2 O + C O ⇄ C O 2 + H 2 (\displaystyle (\mathsf (H_(2)O+CO\rightleftarrows CO_(2)+H_(2))))

up to 830 °C shifted to the right, above 830 °C to the left.

Interestingly, there are bacteria capable of obtaining the energy they need for life due to the oxidation of CO.

Carbon monoxide (II) burns with a blue flame (reaction start temperature 700 ° C) in air:

2 C O + O 2 → 2 C O 2 (\displaystyle (\mathsf (2CO+O_(2)\rightarrow 2CO_(2)))) (Δ G° 298 = −257 kJ, Δ S° 298 = −86 J/K).

The combustion temperature of CO can reach 2100 °C. The combustion reaction is a chain one, and the initiators are small amounts of hydrogen-containing compounds (water, ammonia, hydrogen sulfide, etc.)

Due to such a good calorific value, CO is a component of various technical gas mixtures (see, for example, generator gas) used, among other things, for heating. Explosive when mixed with air; lower and upper concentration limits of flame propagation: from 12.5 to 74% (by volume) .

halogens. The reaction with chlorine has received the greatest practical application:

C O + C l 2 → C O C l 2 . (\displaystyle (\mathsf (CO+Cl_(2)\rightarrow COCl_(2))).)

By reacting CO with F 2 , in addition to COF 2 carbonyl fluoride, a peroxide compound (FCO) 2 O 2 can be obtained. Its characteristics: melting point -42 ° C, boiling point +16 ° C, has a characteristic odor (similar to the smell of ozone), when heated above 200 ° C, it decomposes with an explosion (reaction products CO 2 , O 2 and COF 2), in acidic medium reacts with potassium iodide according to the equation:

(F C O) 2 O 2 + 2 K I → 2 K F + I 2 + 2 C O 2. (\displaystyle (\mathsf ((FCO)_(2)O_(2)+2KI\rightarrow 2KF+I_(2)+2CO_(2).)))

Carbon monoxide(II) reacts with chalcogens. With sulfur it forms carbon sulfide COS, the reaction proceeds when heated, according to the equation:

C O + S → C O S (\displaystyle (\mathsf (CO+S\rightarrow COS))) (Δ G° 298 = −229 kJ, Δ S° 298 = −134 J/K).

Similar carbon selenoxide COSe and carbon telluroxide COTe have also been obtained.

Restores SO 2:

2 C O + S O 2 → 2 C O 2 + S . (\displaystyle (\mathsf (2CO+SO_(2)\rightarrow 2CO_(2)+S.)))

With transition metals, it forms combustible and toxic compounds - carbonyls, such as,,,, etc. Some of them are volatile.

n C O + M e → [ M e (C O) n ] (\displaystyle (\mathsf (nCO+Me\rightarrow )))

Carbon monoxide(II) is slightly soluble in water, but does not react with it. Also, it does not react with solutions of alkalis and acids. However, it reacts with alkali melts to form the corresponding formates:

C O + K O H → H C O O K . (\displaystyle (\mathsf (CO+KOH\rightarrow HCOOK.)))

An interesting reaction is the reaction of carbon monoxide (II) with metallic potassium in an ammonia solution. This forms the explosive compound potassium dioxodicarbonate:

2 K + 2 C O → K 2 C 2 O 2 . (\displaystyle (\mathsf (2K+2CO\rightarrow K_(2)C_(2)O_(2).))) x C O + y H 2 → (\displaystyle (\mathsf (xCO+yH_(2)\rightarrow ))) alcohols + linear alkanes.

This process is the source of critical industrial products such as methanol, synthetic diesel fuel, polyhydric alcohols, oils and lubricants.

Physiological action

Toxicity

Carbon monoxide is highly toxic.

The toxic effect of carbon monoxide (II) is due to the formation of carboxyhemoglobin - a much stronger carbonyl complex with hemoglobin, compared with the complex of hemoglobin with oxygen (oxyhemoglobin). Thus, the processes of oxygen transport and cellular respiration are blocked. Air concentrations greater than 0.1% result in death within one hour.

• The victim should be taken out to fresh air. In case of mild poisoning, hyperventilation of the lungs with oxygen is sufficient.
• Artificial ventilation of the lungs.
• Lobeline or caffeine under the skin.
• Carboxylase intravenously.

World medicine does not know reliable antidotes for use in case of carbon monoxide poisoning.

Protection against carbon monoxide(II)

endogenous carbon monoxide

Endogenous carbon monoxide is produced normally by the cells of the human and animal body and acts as a signaling molecule. It plays a known physiological role in the body, in particular being a neurotransmitter and inducing vasodilation. Due to the role of endogenous carbon monoxide in the body, its metabolic disorders are associated with various diseases, such as neurodegenerative diseases, atherosclerosis of blood vessels, hypertension, heart failure, and various inflammatory processes.

Endogenous carbon monoxide is formed in the body due to the oxidizing action of the heme oxygenase enzyme on heme, which is a product of the destruction of hemoglobin and myoglobin, as well as other heme-containing proteins. This process causes the formation of a small amount of carboxyhemoglobin in the human blood, even if the person does not smoke and breathes not atmospheric air (always containing small amounts of exogenous carbon monoxide), but pure oxygen or a mixture of nitrogen and oxygen.

Following the first evidence that appeared in 1993 that endogenous carbon monoxide is a normal neurotransmitter in the human body, as well as one of three endogenous gases that normally modulate the course of inflammatory reactions in the body (the other two are nitric oxide (II) and hydrogen sulfide ), endogenous carbon monoxide has received considerable attention from clinicians and researchers as an important biological regulator. In many tissues, all three of the aforementioned gases have been shown to be anti-inflammatory agents, vasodilators, and also induce angiogenesis. However, not everything is so simple and unambiguous. Angiogenesis is not always a beneficial effect, since it plays a role in the growth of malignant tumors in particular, and is also one of the causes of retinal damage in macular degeneration. In particular, it is important to note that smoking (the main source of carbon monoxide in the blood, giving several times higher concentration than natural production) increases the risk of macular degeneration of the retina by 4-6 times.

There is a theory that in some synapses of nerve cells, where information is stored for a long time, the receiving cell, in response to the received signal, produces endogenous carbon monoxide, which transmits the signal back to the transmitting cell, which informs it of its readiness to receive signals from it in the future. and increasing the activity of the signal transmitter cell. Some of these nerve cells contain guanylate cyclase, an enzyme that is activated when exposed to endogenous carbon monoxide.

Research on the role of endogenous carbon monoxide as an anti-inflammatory agent and cytoprotector has been carried out in many laboratories around the world. These properties of endogenous carbon monoxide make the effect on its metabolism an interesting therapeutic target for the treatment of various pathological conditions such as tissue damage caused by ischemia and subsequent reperfusion (for example, myocardial infarction, ischemic stroke), transplant rejection, vascular atherosclerosis, severe sepsis , severe malaria , autoimmune diseases. Human clinical trials have also been conducted, but their results have not yet been published.

In summary, what is known as of 2015 about the role of endogenous carbon monoxide in the body can be summarized as follows:

• Endogenous carbon monoxide is one of the important endogenous signaling molecules;
• Endogenous carbon monoxide modulates CNS and cardiovascular functions;
• Endogenous carbon monoxide inhibits platelet aggregation and their adhesion to vessel walls;
• Influencing the exchange of endogenous carbon monoxide in the future may be one of the important therapeutic strategies for a number of diseases.

Discovery history

The toxicity of the smoke emitted during the combustion of coal was described by Aristotle and Galen.

Carbon monoxide (II) was first obtained by the French chemist Jacques de Lasson in the heating of zinc oxide with coal, but was initially mistaken for hydrogen, as it burned with a blue flame.

The fact that this gas contains carbon and oxygen was discovered by the English chemist William Kruikshank. The toxicity of the gas was investigated in 1846 by the French physician Claude Bernard in experiments on dogs.

Carbon monoxide (II) outside the Earth's atmosphere was first discovered by the Belgian scientist M. Mizhot (M. Migeotte) in 1949 by the presence of the main vibrational-rotational band in the IR spectrum of the Sun. Carbon(II) oxide was discovered in the interstellar medium in 1970.

Receipt

industrial way

• It is formed during the combustion of carbon or compounds based on it (for example, gasoline) in conditions of lack of oxygen:

2 C + O 2 → 2 C O (\displaystyle (\mathsf (2C+O_(2)\rightarrow 2CO)))(thermal effect of this reaction is 220 kJ),

• or when reducing carbon dioxide with hot coal:

C O 2 + C ⇄ 2 C O (\displaystyle (\mathsf (CO_(2)+C\rightleftarrows 2CO))) (Δ H= 172 kJ, Δ S= 176 J/K)

This reaction occurs during the furnace furnace, when the furnace damper is closed too early (until the coals have completely burned out). The resulting carbon monoxide (II), due to its toxicity, causes physiological disorders (“burnout”) and even death (see below), hence one of the trivial names - “carbon monoxide”.

The carbon dioxide reduction reaction is reversible, the effect of temperature on the equilibrium state of this reaction is shown in the graph. The flow of the reaction to the right provides the entropy factor, and to the left - the enthalpy factor. At temperatures below 400 °C, the equilibrium is almost completely shifted to the left, and at temperatures above 1000 °C to the right (in the direction of CO formation). At low temperatures, the rate of this reaction is very low; therefore, carbon monoxide (II) is quite stable under normal conditions. This equilibrium has a special name boudoir balance.

• Mixtures of carbon monoxide (II) with other substances are obtained by passing air, water vapor, etc. through a layer of hot coke, coal or brown coal, etc. (see generator gas, water gas, mixed gas, synthesis gas ).

laboratory method

• Decomposition of liquid formic acid under the action of hot concentrated sulfuric acid or passing gaseous formic acid over phosphorus oxide P 2 O 5 . Reaction scheme:

H C O O H → H 2 S O 4 o t H 2 O + C O . (\displaystyle (\mathsf (HCOOH(\xrightarrow[(H_(2)SO_(4))](^(o)t))H_(2)O+CO.))) One can also treat formic acid with chlorosulfonic acid. This reaction proceeds already at ordinary temperature according to the scheme: H C O O H + C l S O 3 H → H 2 S O 4 + H C l + C O . (\displaystyle (\mathsf (HCOOH+ClSO_(3)H\rightarrow H_(2)SO_(4)+HCl+CO\uparrow .)))

• Heating a mixture of oxalic and concentrated sulfuric acids. The reaction goes according to the equation:

H 2 C 2 O 4 → H 2 S O 4 o t C O + C O 2 + H 2 O. (\displaystyle (\mathsf (H_(2)C_(2)O_(4)(\xrightarrow[(H_(2)SO_(4))](^(o)t))CO\uparrow +CO_(2) \uparrow +H_(2)O.)))

• Heating a mixture of potassium hexacyanoferrate(II) with concentrated sulfuric acid. The reaction goes according to the equation:

K 4 [ F e (C N) 6 ] + 6 H 2 S O 4 + 6 H 2 O → o t 2 K 2 S O 4 + F e S O 4 + 3 (N H 4) 2 S O 4 + 6 C O . (\displaystyle (\mathsf (K_(4)+6H_(2)SO_(4)+6H_(2)O(\xrightarrow[()](^(o)t))2K_(2)SO_(4)+ FeSO_(4)+3(NH_(4))_(2)SO_(4)+6CO\uparrow .)))

• Recovery from zinc carbonate by magnesium when heated:

M g + Z n C O 3 → o t M g O + Z n O + C O . (\displaystyle (\mathsf (Mg+ZnCO_(3)(\xrightarrow[()](^(o)t))MgO+ZnO+CO\uparrow .)))

Determination of carbon monoxide (II)

Qualitatively, the presence of CO can be determined by the darkening of palladium chloride solutions (or paper impregnated with this solution). Darkening is associated with the release of finely dispersed metallic palladium according to the scheme:

P d C l 2 + C O + H 2 O → P d ↓ + C O 2 + 2 H C l . (\displaystyle (\mathsf (PdCl_(2)+CO+H_(2)O\rightarrow Pd\downarrow +CO_(2)+2HCl.)))

This reaction is very sensitive. Standard solution: 1 gram of palladium chloride per liter of water.

The quantitative determination of carbon monoxide (II) is based on the iodometric reaction:

5 C O + I 2 O 5 → 5 C O 2 + I 2. (\displaystyle (\mathsf (5CO+I_(2)O_(5)\rightarrow 5CO_(2)+I_(2).)))

Application

• Carbon monoxide(II) is an intermediate reagent used in reactions with hydrogen in the most important industrial processes for the production of organic alcohols and straight hydrocarbons.
• Carbon monoxide (II) is used to process animal meat and fish, giving them a bright red color and a look of freshness, without changing the taste (technologies clear smoke and Tasteless smoke). The permissible concentration of CO is 200 mg/kg of meat.
• Carbon monoxide(II) is the main component of generator gas used as a fuel in natural gas vehicles.
• Carbon monoxide from engine exhaust was used by the Nazis during World War II to massacre people by poisoning.

Carbon monoxide(II) in the Earth's atmosphere

There are natural and anthropogenic sources of entry into the Earth's atmosphere. Under natural conditions, on the Earth's surface, CO is formed during the incomplete anaerobic decomposition of organic compounds and during the combustion of biomass, mainly during forest and steppe fires. Carbon monoxide (II) is formed in the soil both biologically (excreted by living organisms) and non-biologically. The release of carbon monoxide (II) due to phenolic compounds common in soils containing OCH 3 or OH groups in ortho- or para-positions with respect to the first hydroxyl group has been experimentally proven.

The overall balance of production of non-biological CO and its oxidation by microorganisms depends on specific environmental conditions, primarily on humidity and the value of . For example, from arid soils, carbon monoxide(II) is released directly into the atmosphere, thus creating local maxima in the concentration of this gas.

In the atmosphere, CO is the product of chain reactions involving methane and other hydrocarbons (primarily isoprene).

The main anthropogenic source of CO currently is the exhaust gases of internal combustion engines. Carbon monoxide is formed when hydrocarbon fuels are burned in internal combustion engines at insufficient temperatures or a poorly tuned air supply system (insufficient oxygen is supplied to oxidize CO to CO 2 ). In the past, a significant proportion of anthropogenic CO emissions into the atmosphere came from lighting gas used for indoor lighting in the 19th century. In composition, it approximately corresponded to water gas, that is, it contained up to 45% carbon monoxide (II). In the public sector, it is not used due to the presence of a much cheaper and more energy-efficient analogue -

CARBON OXIDE (CARBON MONOXIDE). Carbon(II) oxide (carbon monoxide) CO, non-salt-forming carbon monoxide. This means that there is no acid corresponding to this oxide. Carbon monoxide (II) is a colorless and odorless gas that liquefies at atmospheric pressure at a temperature of -191.5 ° C and solidifies at -205 ° C. The CO molecule is similar in structure to the N2 molecule: both contain an equal number of electrons (such molecules are called isoelectronic) , the atoms in them are connected by a triple bond (two bonds in the CO molecule are formed due to the 2p electrons of carbon and oxygen atoms, and the third one is formed by the donor-acceptor mechanism with the participation of the lone electron pair of oxygen and the free 2p orbital of carbon). As a result, the physical properties of CO and N2 (melting and boiling points, solubility in water, etc.) are very close.

Carbon monoxide (II) is formed during the combustion of carbon-containing compounds with insufficient oxygen access, as well as when hot coal comes into contact with the product of complete combustion - carbon dioxide: C + CO2 → 2CO. In the laboratory, CO is obtained by dehydration of formic acid by the action of concentrated sulfuric acid on liquid formic acid when heated, or by passing vapors of formic acid over P2O5: HCOOH → CO + H2O. CO is obtained by decomposition of oxalic acid: H2C2O4 → CO + CO2 + H2O. It is easy to separate CO from other gases by passing through an alkali solution.
Under normal conditions, CO, like nitrogen, is chemically rather inert. Only at elevated temperatures does CO tend to undergo oxidation, addition, and reduction reactions. So, at elevated temperatures, it reacts with alkalis: CO + NaOH → HCOONa, CO + Ca(OH)2 → CaCO3 + H2. These reactions are used to remove CO from industrial gases.

Carbon monoxide(II) is a high-calorie fuel: combustion is accompanied by the release of a significant amount of heat (283 kJ per 1 mol of CO). Mixtures of CO with air explode at its content from 12 to 74%; Fortunately, in practice, such mixtures are extremely rare. In industry, to obtain CO, gasification of solid fuel is carried out. For example, blowing water vapor through a layer of coal heated to 1000o C leads to the formation of water gas: C + H2O → CO + H2, which has a very high calorific value. However, incineration is far from the most profitable use of water gas. From it, for example, it is possible to obtain (in the presence of various catalysts under pressure) a mixture of solid, liquid and gaseous hydrocarbons - a valuable raw material for the chemical industry (Fischer-Tropsch reaction). From the same mixture, by enriching it with hydrogen and using the necessary catalysts, alcohols, aldehydes, and acids can be obtained. Of particular importance is the synthesis of methanol: CO + 2H2 → CH3OH, the most important raw material for organic synthesis, so this reaction is carried out in industry on a large scale.

Reactions in which CO is a reducing agent can be demonstrated by the example of the reduction of iron from ore during the blast-furnace process: Fe3O4 + 4CO → 3Fe + 4CO2. The reduction of metal oxides with carbon(II) oxide is of great importance in metallurgical processes.

CO molecules are characterized by addition reactions to transition metals and their compounds with the formation of complex compounds - carbonyls. Examples are liquid or solid metal carbonyls Fe(CO)4, Fe(CO)5, Fe2(CO)9, Ni(CO)4, Cr(CO)6, etc. metal and CO. In this way, powdered metals of high purity can be obtained. Sometimes metal “streaks” are visible on the burner of a gas stove; this is a consequence of the formation and decay of iron carbonyl. At present, thousands of various metal carbonyls have been synthesized containing, in addition to CO, inorganic and organic ligands, for example, PtCl2(CO), K3, Cr(C6H5Cl)(CO)3.

CO is also characterized by the reaction of the compound with chlorine, which in the light proceeds already at room temperature with the formation of extremely toxic phosgene: CO + Cl2 → COCl2. This reaction is a chain one, it follows a radical mechanism involving chlorine atoms and COCl free radicals. Despite its toxicity, phosgene is widely used in the synthesis of many organic compounds.

Carbon monoxide (II) is a strong poison, as it forms strong complexes with metal-containing biologically active molecules; at the same time tissue respiration is disturbed. The cells of the central nervous system are especially affected. The binding of CO to Fe(II) atoms in blood hemoglobin prevents the formation of oxyhemoglobin, which carries oxygen from the lungs to the tissues. Already at a content of 0.1% CO in the air, this gas displaces half of the oxygen from oxyhemoglobin. In the presence of CO, death by asphyxiation can occur even in the presence of large amounts of oxygen. Therefore, CO is called carbon monoxide. In an "angred" person, the brain and nervous system are primarily affected. For salvation, first of all, clean air is needed that does not contain CO (or even better - pure oxygen), while the CO associated with hemoglobin is gradually replaced by O2 molecules and suffocation disappears. The maximum allowable average daily concentration of CO in the atmospheric air is 3 mg/m3 (about 3.10–5%), and in the air of the working zone it is 20 mg/m3.

Usually, the content of CO in the atmosphere does not exceed 10–5%. This gas enters the air as part of volcanic and marsh gases, with the secretions of plankton and other microorganisms. Thus, 220 million tons of CO2 are emitted annually from the surface layers of the ocean into the atmosphere. The concentration of CO in coal mines is high. A lot of carbon monoxide is produced during forest fires. The smelting of each million tons of steel is accompanied by the formation of 300 - 400 tons of CO. In total, the technogenic release of CO into the air reaches 600 million tons per year, of which more than half is accounted for by vehicles. With an unadjusted carburetor, up to 12% CO can be contained in the exhaust gases! Therefore, in most countries, strict standards have been introduced for the content of CO in the exhaust of cars.

The formation of CO always occurs during the combustion of carbon-containing compounds, including wood, with insufficient access to oxygen, as well as when hot coal comes into contact with carbon dioxide: C + CO2 → 2CO. Such processes also occur in rural ovens. Therefore, closing the stove chimney prematurely to keep the heat in often results in carbon monoxide poisoning. It should not be thought that citizens who do not heat stoves are insured against CO poisoning; for example, it is easy for them to get poisoned in a poorly ventilated garage where a car with a running engine is standing. CO is also contained in the combustion products of natural gas in the kitchen. Many aviation accidents in the past occurred due to engine wear or poor adjustment: CO entered the cockpit and poisoned the crew. The danger is exacerbated by the fact that CO cannot be detected by smell; In this respect, carbon monoxide is more dangerous than chlorine!

Carbon monoxide (II) is practically not sorbed by active carbon and therefore a conventional gas mask does not save from this gas; to absorb it, an additional hopcalite cartridge is needed, containing a catalyst that “afterburns” CO to CO2 with the help of atmospheric oxygen. More and more passenger cars are now supplied with afterburning catalysts, despite the high cost of these catalysts based on platinum metals.

Publication date 28.01.2012 12:18

Carbon monoxide- carbon monoxide, which is too often heard when it comes to poisoning by combustion products, accidents in industry or even at home. Due to the special toxic properties of this compound, an ordinary home gas water heater can cause the death of an entire family. There are hundreds of examples of this. But why is this happening? What is carbon monoxide, really? Why is it dangerous for humans?

What is carbon monoxide, formula, basic properties

Carbon monoxide formula which is very simple and denotes the union of an oxygen atom and carbon - CO, - one of the most toxic gaseous compounds. But unlike many other hazardous substances that are used only for narrow industrial purposes, carbon monoxide chemical contamination can occur during completely ordinary chemical processes, even in everyday life.

However, before moving on to how the synthesis of this substance occurs, consider what is carbon monoxide in general and what are its main physical properties:

• colorless gas without taste and smell;
• extremely low melting and boiling points: -205 and -191.5 degrees Celsius, respectively;
• density 0.00125 g/cc;
• highly combustible with a high combustion temperature (up to 2100 degrees Celsius).

Carbon monoxide formation

In home or industry carbon monoxide formation usually occurs in one of several fairly simple ways, which easily explains the risk of accidental synthesis of this substance with a risk to the personnel of the enterprise or residents of the house where the heating equipment has malfunctioned or safety has been violated. Consider the main ways of formation of carbon monoxide:

• combustion of carbon (coal, coke) or its compounds (gasoline and other liquid fuels) in conditions of lack of oxygen. As you might guess, a lack of fresh air, dangerous from the point of view of the risk of carbon monoxide synthesis, easily occurs in internal combustion engines, domestic columns with impaired ventilation, industrial and conventional furnaces;
• interaction of ordinary carbon dioxide with hot coal. Such processes occur in the furnace constantly and are completely reversible, but, given the already mentioned lack of oxygen, with the damper closed, carbon monoxide is formed in much larger quantities, which is a mortal danger to people.

Why is carbon monoxide dangerous?

In sufficient concentration carbon monoxide properties which is explained by its high chemical activity, is extremely dangerous for human life and health. The essence of such poisoning lies, first of all, in the fact that the molecules of this compound instantly bind blood hemoglobin and deprive it of its ability to carry oxygen. Thus, carbon monoxide reduces the level of cellular respiration with the most serious consequences for the body.

Answering the question " Why is carbon monoxide dangerous?"It is worth mentioning that, unlike many other toxic substances, a person does not feel any specific smell, does not experience discomfort and is not able to recognize its presence in the air by any other means, without special equipment. As a result, the victim simply does not take no measures to escape, and when the effects of carbon monoxide (drowsiness and unconsciousness) become apparent, it may be too late.

Carbon monoxide is fatal within an hour at air concentrations above 0.1%. At the same time, the exhaust of a completely ordinary passenger car contains from 1.5 to 3% of this substance. And that's assuming the engine is in good condition. This easily explains the fact that carbon monoxide poisoning often occurs precisely in garages or inside a car sealed with snow.

Other most dangerous cases in which people have been poisoned by carbon monoxide at home or at work are ...

• overlap or breakdown of the ventilation of the heating column;
• illiterate use of wood or coal stoves;
• on fires in enclosed spaces;
• close to busy highways;
• at industrial enterprises where carbon monoxide is actively used.

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

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

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

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

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

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

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

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

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

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