Signs that carbon monoxide (carbon monoxide (II), carbon monoxide, carbon monoxide) has formed in the air in dangerous concentrations are difficult to determine - invisible, may not smell, accumulates in the room gradually, imperceptibly. It is extremely dangerous for human life: it has a high toxicity, excessive content in the lungs leads to severe poisoning and deaths. Every year, a high death rate from gas poisoning is recorded. The risk of poisoning can be reduced by following simple rules and the use of special carbon monoxide sensors.
What is carbon monoxide
Natural gas is formed during the combustion of any biomass, in industry it is a combustion product of any carbon-based compounds. In both cases, a prerequisite for gas evolution 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 the cells of the human body.
Properties
In terms of monoxide chemistry - inorganic compound with a single oxygen atom in the molecule, the chemical formula is CO. It is a chemical substance that does not have a characteristic color, taste and smell, it is lighter than air, but heavier than hydrogen, and is inactive at room temperature. A person who smells, feels only the presence of organic impurities in the air. Belongs to the category of toxic products, death at a concentration in the air of 0.1% occurs within one hour. The characteristic of the maximum permissible concentration is 20 mg / m3.
The effect of carbon monoxide on the human body
For humans, carbon monoxide is a deadly hazard. 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. High level the content 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, destruction in a natural way is possible within 4-6 hours. At high concentrations, only medical preparations.
Carbon monoxide poisoning
Carbon monoxide is one of the most hazardous substances. In case of poisoning, intoxication of the body occurs, accompanied by deterioration general condition 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 on how soon help arrived. In this case, minutes count - the victim can either recover completely, or remain sick forever (it all depends on the speed of the rescuers' response).
Symptoms
Depending on the degree of poisoning, headaches, dizziness, tinnitus, heart palpitations, nausea, shortness of breath, flickering in the eyes, general weakness can be observed. Drowsiness is often observed, which is especially dangerous when a person is in a gassed room. In case of inhalation a large number toxic substances there are convulsions, loss of consciousness, in especially severe cases - coma.
First aid for carbon monoxide poisoning
First aid should be provided to the victim on the spot in case of carbon monoxide poisoning. We must immediately move it to Fresh air and call a doctor. You should also remember about your safety: you need to enter a room with a source of this substance only by inhaling deeply, do not breathe inside. Until the doctor arrives, it is necessary to facilitate the access of oxygen to the lungs: unfasten buttons, remove or loosen clothes. If the victim has lost consciousness and stopped breathing, artificial ventilation of the lungs is necessary.
Antidote for poisoning
A special antidote (antidote) for carbon monoxide poisoning is drug preparation, which actively prevents the formation of carboxyhemoglobin. The action of the antidote leads to a decrease in the body's need for oxygen, support for organs sensitive to a lack of oxygen: the brain, liver, etc. It is administered intramuscularly at a dosage of 1 ml immediately after the patient is removed from the area with a high concentration of toxic substances. You can re-enter the antidote no earlier than an hour after the first injection. It can be used for prevention.
Treatment
In the 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. The level of gas in the blood is constantly monitored. Further rehabilitation is medical, the actions of doctors are aimed at restoring the functioning of the brain, cardiovascular system, and lungs.
Effects
Exposure to carbon monoxide in the body can cause serious illnesses: the working capacity of the brain, behavior, consciousness of a person change, inexplicable headaches appear. Memory is especially affected by harmful substances - that part of the brain that is responsible for the transition short term memory in the long term. The patient may feel the consequences of carbon monoxide poisoning only after a few weeks. Most victims fully recover after a period of rehabilitation, but some feel the consequences for a lifetime.
How to detect carbon monoxide in a room
Carbon monoxide poisoning is easy at home, and it doesn't just happen during a fire. The concentration of carbon monoxide is formed by careless handling of the stove damper, during the operation of a faulty geyser or ventilation. A gas stove can be a source of carbon monoxide. If there is smoke in the room, this is already a reason to sound the alarm. For constant monitoring of the gas level, there are special sensors. They monitor the level of gas concentration and report the excess of the norm. The presence of such a device reduces the risk of poisoning.
Video
The physical properties of carbon monoxide (carbon monoxide CO) at normal atmospheric pressure depending on the temperature at its negative and positive values.
In tables the following physical properties of CO are presented: carbon monoxide density ρ , specific heat at constant pressure Cp, thermal conductivity coefficients λ and dynamic viscosity μ .
The first table shows the density and specific heat of carbon monoxide CO in the temperature range from -73 to 2727°C.
The second table gives the values of such physical properties of carbon monoxide as thermal conductivity and its dynamic viscosity in the temperature range from minus 200 to 1000°C.
The density of carbon monoxide, as well as, depends significantly on temperature - when carbon monoxide CO is heated, its density decreases. For example, at room temperature, the density of carbon monoxide is 1.129 kg / m 3, but in the process of heating to a temperature of 1000 ° C, the density of this gas decreases by 4.2 times - to a value of 0.268 kg / m 3.
Under normal conditions (temperature 0°C) carbon monoxide has a density of 1.25 kg/m 3 . If we compare its density with or other common gases, then the density of carbon monoxide relative to air is less important - carbon monoxide is lighter than air. It is also lighter than argon, but heavier than nitrogen, hydrogen, helium and other light gases.
The specific heat capacity of carbon monoxide under normal conditions is 1040 J/(kg deg). As the temperature of this gas rises, its specific heat capacity increases. For example, at 2727°C its value is 1329 J/(kg deg).
| t, °С | ρ, kg / m 3 | C p , J/(kg deg) | t, °С | ρ, kg / m 3 | C p , J/(kg deg) | t, °С | ρ, kg / m 3 | C p , J/(kg deg) |
|---|---|---|---|---|---|---|---|---|
| -73 | 1,689 | 1045 | 157 | 0,783 | 1053 | 1227 | 0,224 | 1258 |
| -53 | 1,534 | 1044 | 200 | 0,723 | 1058 | 1327 | 0,21 | 1267 |
| -33 | 1,406 | 1043 | 257 | 0,635 | 1071 | 1427 | 0,198 | 1275 |
| -13 | 1,297 | 1043 | 300 | 0,596 | 1080 | 1527 | 0,187 | 1283 |
| -3 | 1,249 | 1043 | 357 | 0,535 | 1095 | 1627 | 0,177 | 1289 |
| 0 | 1,25 | 1040 | 400 | 0,508 | 1106 | 1727 | 0,168 | 1295 |
| 7 | 1,204 | 1042 | 457 | 0,461 | 1122 | 1827 | 0,16 | 1299 |
| 17 | 1,162 | 1043 | 500 | 0,442 | 1132 | 1927 | 0,153 | 1304 |
| 27 | 1,123 | 1043 | 577 | 0,396 | 1152 | 2027 | 0,147 | 1308 |
| 37 | 1,087 | 1043 | 627 | 0,374 | 1164 | 2127 | 0,14 | 1312 |
| 47 | 1,053 | 1043 | 677 | 0,354 | 1175 | 2227 | 0,134 | 1315 |
| 57 | 1,021 | 1044 | 727 | 0,337 | 1185 | 2327 | 0,129 | 1319 |
| 67 | 0,991 | 1044 | 827 | 0,306 | 1204 | 2427 | 0,125 | 1322 |
| 77 | 0,952 | 1045 | 927 | 0,281 | 1221 | 2527 | 0,12 | 1324 |
| 87 | 0,936 | 1045 | 1027 | 0,259 | 1235 | 2627 | 0,116 | 1327 |
| 100 | 0,916 | 1045 | 1127 | 0,241 | 1247 | 2727 | 0,112 | 1329 |
The thermal conductivity of carbon monoxide under normal conditions is 0.02326 W/(m deg). It increases with its temperature and at 1000°C becomes equal to 0.0806 W/(m deg). It should be noted that the thermal conductivity of carbon monoxide is slightly less than this value y.
The dynamic viscosity of carbon monoxide at room temperature is 0.0246·10 -7 Pa·s. When carbon monoxide is heated, its viscosity increases. Such a character of the dependence of dynamic viscosity on temperature is observed in . It should be noted that carbon monoxide is more viscous than water vapor and carbon dioxide CO 2 , but has a lower viscosity compared to nitric oxide NO and air.
Oxides of carbon
In recent years, pedagogical science has given preference to personality-oriented learning. The formation of individual personality traits occurs in the process of activity: study, play, work. So an important factor learning is the organization of the learning process, the nature of the relationship between teachers and students and students among themselves. Based on these ideas, I am trying to build the educational process in a special way. At the same time, each student chooses his own pace of studying the material, has the opportunity to work at an accessible level, in a situation of success. At the lesson, it is possible to master and improve not only subject, but also such general educational skills and abilities as staging learning goal, the choice of means and ways to achieve it, the exercise of control over their achievements, the correction of errors. Students learn to work with literature, make notes, diagrams, drawings, work in a group, in pairs, individually, conduct a constructive exchange of opinions, reason logically and draw conclusions.
It is not easy to conduct such lessons, but if you succeed, you feel satisfaction. I offer the scenario of one of my lessons. It was attended by colleagues, administration and a psychologist.
Lesson type. Learning new material.
Goals. Based on motivation and actualization basic knowledge and students' skills to consider the structure, physical and chemical properties, the production and use of carbon monoxide and carbon dioxide.
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Equipment and reagents.“Programmed Interrogation” cards, poster diagram, devices for obtaining gases, glasses, test tubes, fire extinguisher, matches; lime water, sodium oxide, chalk, hydrochloric acid, indicator solutions, H 2 SO 4 (conc.), HCOOH, Fe 2 O 3 .
Poster scheme
"The structure of the carbon monoxide molecule (carbon(II)) CO"
DURING THE CLASSES
Tables for students in the classroom are arranged in a circle. The teacher and students have the opportunity to freely move to the laboratory tables (1, 2, 3). For the lesson, children sit at study tables (4, 5, 6, 7, ...) with each other at will (free groups of 4 people).
Teacher. Wise Chinese proverb(written beautifully on the board) says:
"I hear - I forget,
I see - I remember
I do - I understand.
Do you agree with the conclusions of the Chinese sages?
And what Russian proverbs reflect Chinese wisdom?
Children give examples.
Teacher. Indeed, only by creating, by creating, you can get valuable product: new substances, devices, machines, as well as intangible values - conclusions, generalizations, conclusions. I invite you today to take part in the study of the properties of two substances. It is known that during the technical inspection of the car, the driver provides a certificate on the state of the exhaust gases of the car. The concentration of what gas is indicated in the certificate?
(O t in e t. CO.)
Student. This gas is poisonous. Getting into the blood, it causes poisoning of the body (“burning out”, hence the name of the oxide - carbon monoxide). In life-threatening quantities, it is found in car exhaust gases.(reads a report from the newspaper that the driver, who fell asleep to death while the engine was running in the garage, died to death). The antidote for carbon monoxide poisoning is breathing fresh air and pure oxygen. Another carbon monoxide is carbon dioxide.
Teacher. There is a Programmed Poll card on your desks. Familiarize yourself with its contents and on a clean sheet of paper mark the numbers of those tasks, the answers to which you know based on your life experience. Opposite the task-statement number, write the formula of carbon monoxide to which this statement refers.
Student consultants (2 people) collect answer sheets and, based on the results of the answers, form new groups for further work.
Programmed survey "Carbon oxides"
1. The molecule of this oxide consists of one carbon atom and one oxygen atom.
2. The bond between atoms in a molecule is covalent polar.
3. A gas that is practically insoluble in water.
4. This oxide molecule has one carbon atom and two oxygen atoms.
5. It has no odor or color.
6. A gas soluble in water.
7. Does not liquefy even at -190 °C ( t bp = –191.5 °С).
8. Acid oxide.
9. Easily compressed, at 20 °C under a pressure of 58.5 atm it becomes liquid, solidifies into "dry ice".
10. Not poisonous.
11. Non-salt forming.
12. combustible
13. Interacts with water.
14. Reacts with basic oxides.
15. Reacts with metal oxides, restoring free metals from them.
16. Obtained by the interaction of acids with salts of carbonic acid.
17. I.
18. Interacts with alkalis.
19. The source of carbon absorbed by plants in greenhouses and greenhouses leads to an increase in yield.
20. Used in the carbonation of water and drinks.
Teacher. Review the content of the card again. Group the information into 4 blocks:
structure,
physical properties,
Chemical properties,
receipt.
The teacher provides an opportunity to speak to each group of students, summarizes the speeches. Then the students different groups choose their work plan - the order of studying oxides. To this end, they number blocks of information and justify their choice. The order of study may be as written above, or with any other combination of the four blocks marked.
The teacher draws students' attention to the key points of the topic. Since carbon oxides gaseous substances must be handled with care (safety regulations). The teacher approves the plan of each group and distributes consultants (pre-prepared students).
Demonstration experiments
1. Pouring carbon dioxide from glass to glass.
2. Extinguishing candles in a glass as CO 2 accumulates.
3. Drop a few small pieces of "dry ice" into a glass of water. The water will boil, and thick white smoke will pour out of it.
CO 2 gas is already liquefied at room temperature under a pressure of 6 MPa. In the liquid state, it is stored and transported in steel cylinders. If you open the valve of such a cylinder, then liquid CO 2 will begin to evaporate, due to which strong cooling occurs and part of the gas turns into a snow-like mass - “dry ice”, which is pressed and used to store ice cream.
4. Demonstration of a chemical foam fire extinguisher (OHP) and an explanation of the principle of its operation using a model - test tubes with a stopper and a gas outlet tube.
Information on structure at table number 1 (instruction cards 1 and 2, the structure of CO and CO 2 molecules).
Information about physical properties- at table number 2 (work with a textbook - Gabrielyan O.S. Chemistry-9. M.: Bustard, 2002, p. 134–135).
Data about receiving and chemical properties - on tables No. 3 and 4 (instruction cards 3 and 4, instructions for conducting practical work, pp. 149–150 of the textbook).
Practical work Put a few pieces of chalk or marble into a test tube and add a little dilute hydrochloric acid. Quickly close the test tube with a stopper with a gas outlet tube. Lower the end of the tube into another test tube containing 2–3 ml of lime water. Watch for a few minutes as gas bubbles pass through the lime water. Then remove the end of the vent tube from the solution and rinse it in distilled water. Dip the tube into another test tube with 2-3 ml of distilled water and pass the gas through it. After a few minutes, remove the tube from the solution, add a few drops of blue litmus to the resulting solution. Pour 2–3 ml of a dilute sodium hydroxide solution into a test tube and add a few drops of phenolphthalein to it. Then pass the gas through the solution. Answer the questions. Questions 1. What happens if chalk or marble is affected hydrochloric acid? 2. Why, when carbon dioxide is passed through lime water, the solution first becomes cloudy, and then the lime dissolves? 3. What happens when carbon(IV) oxide is passed through distilled water? Write the equations for the corresponding reactions in molecular, ionic, and ion-abbreviated forms. Recognition of carbonates The four test tubes given to you contain crystalline substances: sodium sulfate, zinc chloride, potassium carbonate, sodium silicate. Determine which substance is in each test tube. Write reaction equations in molecular, ionic, and abbreviated ionic forms. |
Homework
The teacher suggests taking the “Programmed Interview” card home and, in preparation for the next lesson, consider ways to obtain information. (How did you know that the gas under study liquefies, reacts with acid, is poisonous, etc.?)
Independent work of students
practical work groups of children perform with different speed. Therefore, those who complete the work faster are offered games.
Fifth extra
Four substances can have something in common, and the fifth substance is out of line, superfluous.
1. Carbon, diamond, graphite, carbide, carbine. (Carbide.)
2. Anthracite, peat, coke, oil, glass. (Glass.)
3. Limestone, chalk, marble, malachite, calcite. (Malachite.)
4. Crystalline soda, marble, potash, caustic, malachite. (Caustic.)
5. Phosgene, phosphine, hydrocyanic acid, potassium cyanide, carbon disulfide. (Phosphine.)
6. Sea water, mineral water, distilled water, ground water, hard water. (Distilled water.)
7. Lime milk, fluff, slaked lime, limestone, lime water. (Limestone.)
8. Li 2 CO 3; (NH 4) 2 CO 3; CaCO 3 ; K 2 CO 3 , Na 2 CO 3 . (CaCO 3 .)
Synonyms
Write chemical formulas substances or their names.
1. Halogen - ... (Chlorine or bromine.)
2. Magnesite - ... (MgCO 3 .)
3. Urea - ... ( Urea H2NC(O)NH2.)
4. Potash - ... (K 2 CO 3 .)
5. Dry ice - ... (CO 2 .)
6. Hydrogen oxide - ... ( Water.)
7. Ammonia - ... ( 10% aqueous ammonia solution.)
8. Salts of nitric acid - ... ( Nitrates- KNO 3 , Ca(NO 3) 2 , NaNO 3 .)
9. Natural gas - ... ( Methane CH 4 .)
Antonyms
Write chemical terms that are opposite in meaning to the suggested ones.
1. Oxidizer - ... ( Reducing agent.)
2. Electron donor - ... ( electron acceptor.)
3. Acid properties – … (Basic properties.)
4. Dissociation - ... ( Association.)
5. Adsorption - ... ( Desorption.)
6. Anode - ... ( Cathode.)
7. Anion - ... ( Cation.)
8. Metal - ... ( Non-metal.)
9. Starting substances - ... ( reaction products.)
Search for patterns
Establish a sign that unites the indicated substances and phenomena.
1. Diamond, carbine, graphite - ... ( Allotropic modifications of carbon.)
2. Glass, cement, brick - ... ( Construction Materials.)
3. Breathing, decay, volcanic eruption - ... ( Processes accompanied by the release of carbon dioxide.)
4. CO, CO 2, CH 4, SiH 4 - ... ( Compounds of elements of group IV.)
5. NaHCO 3, CaCO 3, CO 2, H 2 CO 3 - ... ( Oxygen compounds of carbon.)
Carbon monoxide, carbon monoxide (CO) is a colorless, odorless and tasteless gas that is slightly less dense than air. It is toxic to hemoglobin animals (including humans) if concentrations are above about 35 ppm, although it is also produced in normal animal metabolism in small amounts, and is thought to have some normal biological functions. In the atmosphere, it is spatially variable and rapidly decaying, and has a role in the formation of ozone at ground level. Carbon monoxide is made up of one carbon atom and one oxygen atom linked by a triple bond, which consists of two covalent bonds as well as one dative covalent bond. It is the simplest carbon monoxide. It is isoelectronic with the cyanide anion, the nitrosonium cation, and molecular nitrogen. In coordination complexes, the carbon monoxide ligand is called the carbonyl.
Story
Aristotle (384-322 BC) first described the process of burning coal, which leads to the formation of toxic fumes. In ancient times, there was a method of execution - to close the criminal in a bathroom with smoldering coals. However, at that time the mechanism of death was unclear. The Greek physician Galen (AD 129-199) suggested that there was a change in the composition of the air that harmed a person when inhaled. In 1776, the French chemist de Lasson produced CO by heating zinc oxide with coke, but the scientist erroneously concluded that the gaseous product was hydrogen because it burned with a blue flame. The gas was identified as a compound containing carbon and oxygen by the Scottish chemist William Cumberland Cruikshank in 1800. Its toxicity in dogs was extensively studied by Claude Bernard around 1846. During World War II, a gas mixture containing carbon monoxide was used to maintain mechanical Vehicle operating in parts of the world where gasoline and diesel were scarce. External (with some exceptions) charcoal or wood-derived gas generators were installed and a mixture of atmospheric nitrogen, carbon monoxide and small amounts of other gasification gases was fed to the gas mixer. The gas mixture resulting from this process is known as wood gas. Carbon monoxide was also used on a large scale during the Holocaust in some German Nazi death camps, most notably in the Chelmno gas vans and in the T4 "euthanasia" killing program.
Sources
Carbon monoxide is formed during the partial oxidation of carbon-containing compounds; it forms when there is not enough oxygen to form carbon dioxide (CO2), such as when working on a stove or internal combustion engine, in an enclosed space. In the presence of oxygen, including atmospheric concentrations, carbon monoxide burns with a blue flame, producing carbon dioxide. Coal gas, which was widely used until the 1960s for indoor lighting, cooking and heating, contained carbon monoxide as a significant fuel component. Some processes in modern technology, such as iron smelting, still produce carbon monoxide as a by-product. Worldwide, the largest sources of carbon monoxide are natural sources, due to photochemical reactions in the troposphere, which generate about 5 × 1012 kg of carbon monoxide per year. Other natural springs COs include volcanoes, forest fires, and other forms of combustion. In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on heme from the breakdown of hemoglobin. This process produces a certain amount of carboxyhemoglobin in normal people, even if they do not inhale carbon monoxide. Since the first report that carbon monoxide was a normal neurotransmitter in 1993, as well as one of three gases that naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has gained great attention scientists as a biological regulator. In many tissues, all three gases act as anti-inflammatory agents, vasodilators, and promoters of neovascular growth. Clinical trials are ongoing for small amounts of carbon monoxide as a medicinal product. However, excessive amounts of carbon monoxide cause carbon monoxide poisoning.
Molecular Properties
Carbon monoxide has a molecular weight of 28.0, making it slightly lighter than air, which has an average molecular weight of 28.8. According to the ideal gas law, CO is therefore less dense than air. The bond length between the carbon atom and the oxygen atom is 112.8 pm. This bond length is consistent with a triple bond, as in molecular nitrogen(N2), which has a similar bond length and almost the same molecular weight. The carbon-oxygen double bonds are much longer, for example 120.8 m for formaldehyde. The boiling point (82 K) and melting point (68 K) are very similar to N2 (77 K and 63 K, respectively). The bond dissociation energy of 1072 kJ/mol is stronger than that of N2 (942 kJ/mol) and represents the strongest known chemical bond. The ground state of the carbon monoxide electron is singlet, as there are no unpaired electrons.
Bonding and dipole moment
Carbon and oxygen together have a total of 10 electrons in the valence shell. Following the octet rule for carbon and oxygen, two atoms form a triple bond, with six electrons in common in three bonding molecular orbitals, rather than the usual double bond found in organic carbonyl compounds. Since four of the shared electrons come from the oxygen atom and only two from the carbon, one bonding orbital is occupied by two electrons from the oxygen atoms, forming a dative or dipole bond. This results in a C ← O polarization of the molecule, with a small negative charge on carbon and a small positive charge on oxygen. The other two bonding orbitals each occupy one electron from carbon and one from oxygen, forming (polar) covalent bonds with reverse C → O polarization, since oxygen is more electronegative than carbon. In free carbon monoxide, the net negative charge δ- remains at the carbon end, and the molecule has a small dipole moment of 0.122 D. Thus, the molecule is asymmetric: oxygen has more electron density than carbon, and also a small positive charge, compared to carbon, which is negative. In contrast, the isoelectronic dinitrogen molecule does not have a dipole moment. If carbon monoxide acts as a ligand, the polarity of the dipole can reverse with a net negative charge at the oxygen end, depending on the structure of the coordination complex.
Bond polarity and oxidation state
Theoretical and experimental studies show that, despite the greater electronegativity of oxygen, the dipole moment proceeds from the more negative end of carbon to the more positive end of oxygen. These three bonds are actually polar covalent bonds that are highly polarized. The calculated polarization to the oxygen atom is 71% for the σ bond and 77% for both π bonds. The oxidation state of carbon to carbon monoxide in each of these structures is +2. It is calculated as follows: all bonding electrons are considered to belong to more electronegative oxygen atoms. Only two non-bonding electrons on carbon are assigned to carbon. In this count, carbon has only two valence electrons in the molecule compared to four in a free atom.
Biological and physiological properties
Toxicity
Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. Carbon monoxide is a colorless substance, odorless and tasteless, but highly toxic. It combines with hemoglobin to form carboxyhemoglobin, which "usurps" the site in hemoglobin that normally carries oxygen but is inefficient for delivering oxygen to body tissues. Concentrations as low as 667 ppm can cause up to 50% of the body's hemoglobin to be converted to carboxyhemoglobin. 50% carboxyhemoglobin levels can lead to convulsions, coma and death. In the United States, the Department of Labor limits long-term levels of carbon monoxide exposure in the workplace to 50 parts per million. For a short period of time, absorption of carbon monoxide is cumulative, as its half-life is about 5 hours in fresh air. The most common symptoms of carbon monoxide poisoning can be similar to other types of poisoning and infections, and include symptoms such as headache, nausea, vomiting, dizziness, fatigue and a feeling of weakness. Affected families often believe they are victims of food poisoning. Babies can be irritable and feed poorly. Neurological symptoms include confusion, disorientation, blurred vision, fainting (loss of consciousness), and seizures. Some descriptions of carbon monoxide poisoning include retinal hemorrhage as well as an abnormal cherry-red color to the blood. In most clinical diagnoses, these features are rare. One of the difficulties with the usefulness of this "cherry" effect is that it corrects, or masks, an otherwise unhealthy appearance, since the main effect of removing venous hemoglobin is to make the suffocated person appear more normal, or dead man seems alive, similar to the effect of red dyes in embalming composition. This staining effect in anoxic CO-poisoned tissue is due to the commercial use of carbon monoxide in meat staining. Carbon monoxide also binds to other molecules such as myoglobin and mitochondrial cytochrome oxidase. Exposure to carbon monoxide can cause significant damage to the heart and central nervous system, especially in the globus pallidus, often associated with long-term chronic conditions. Carbon monoxide can have serious adverse effects on the fetus of a pregnant woman.
normal human physiology
Carbon monoxide is produced naturally in the human body as a signaling molecule. Thus, carbon monoxide may have a physiological role in the body as a neurotransmitter or relaxant. blood vessels. Due to the role of carbon monoxide in the body, abnormalities in its metabolism are associated with various diseases, including neurodegeneration, hypertension, heart failure, and inflammation.
CO functions as an endogenous signaling molecule.
CO modulates the functions of the cardiovascular system
CO inhibits platelet aggregation and adhesion
CO may play a role as a potential therapeutic agent
Microbiology
Carbon monoxide is a breeding ground for methanogenic archaea, a building block for acetyl coenzyme A. This is a topic for new area bioorganometallic chemistry. Extremophilic microorganisms can thus metabolize carbon monoxide in places such as the heat vents of volcanoes. In bacteria, carbon monoxide is produced by the reduction of carbon dioxide by the enzyme carbon monoxide dehydrogenase, a Fe-Ni-S-containing protein. CooA is a carbon monoxide receptor protein. Scope of it biological activity is still unknown. It may be part of the signaling pathway in bacteria and archaea. Its prevalence in mammals has not been established.
Prevalence
Carbon monoxide is found in various natural and man-made environments.
Carbon monoxide is present in small amounts in the atmosphere, mainly as a product of volcanic activity, but is also a product of natural and man-made fires (for example, forest fires, burning of plant residues, and burning sugar cane). The burning of fossil fuels also contributes to the formation of carbon monoxide. Carbon monoxide is found in dissolved form in molten volcanic rocks during high pressures in the Earth's mantle. Because natural sources of carbon monoxide are variable, it is extremely difficult to accurately measure natural gas emissions. Carbon monoxide is a rapidly decaying greenhouse gas and also exerts indirect radiative forcing by increasing concentrations of methane and tropospheric ozone through chemical reactions with other atmospheric constituents (e.g. hydroxyl radical, OH) that would otherwise destroy them. As a result of natural processes in the atmosphere, it is eventually oxidized to carbon dioxide. Carbon monoxide is both short-lived in the atmosphere (lasts about two months on average) and has a spatially variable concentration. In the atmosphere of Venus, carbon monoxide is created as a result of the photodissociation of carbon dioxide electromagnetic radiation with a wavelength shorter than 169 nm. Because of its long lifespan in the middle troposphere, carbon monoxide is also used as a transport tracer for pollutant plumes.
Urban pollution
Carbon monoxide is a temporary atmospheric pollutant in some urban areas, mainly from the exhaust pipes of internal combustion engines (including vehicles, portable and standby generators, lawn mowers, washing machines, etc.) and from incomplete combustion various other fuels (including firewood, coal, charcoal, oil, wax, propane, natural gas, and garbage). Large CO pollution can be observed from space over cities.
Role in the formation of ground-level ozone
Carbon monoxide, along with aldehydes, is part of a series of cycles of chemical reactions that form photochemical smog. It reacts with the hydroxyl radical (OH) to give the radical intermediate HOCO, which rapidly transfers the radical hydrogen O2 to form a peroxide radical (HO2) and carbon dioxide (CO2). The peroxide radical then reacts with nitric oxide (NO) to form nitrogen dioxide (NO2) and a hydroxyl radical. NO 2 gives O(3P) through photolysis, thereby forming O3 after reacting with O2. Since the hydroxyl radical is formed during the formation of NO2, the balance of the sequence of chemical reactions, starting with carbon monoxide, leads to the formation of ozone: CO + 2O2 + hν → CO2 + O3 (Where hν refers to the photon of light absorbed by the NO2 molecule in the sequence) Although the creation NO2 is an important step in producing low level ozone, it also increases the amount of ozone in another, somewhat mutually exclusive way, by reducing the amount of NO that is available to react with ozone.
indoor air pollution
In enclosed environments, the concentration of carbon monoxide can easily rise to lethal levels. On average, 170 people die every year in the United States from non-automotive consumer products that produce carbon monoxide. However, according to the Florida Department of Health, “More than 500 Americans die each year from accidental exposure to carbon monoxide and thousands more in the US require emergency care. medical care with non-fatal carbon monoxide poisoning. These products include faulty fuel combustion appliances such as stoves, cookers, water heaters, and gas and kerosene room heaters; mechanically driven equipment such as portable generators; fireplaces; and charcoal, which is burned in homes and other enclosed spaces. The American Association of Poison Control Centers (AAPCC) reported 15,769 cases of carbon monoxide poisoning, which resulted in 39 deaths in 2007. In 2005, CPSC reported 94 deaths related to carbon monoxide poisoning from a generator. Forty-seven of these deaths occurred during power outages due to severe weather conditions including due to Hurricane Katrina. However, people are dying from carbon monoxide poisoning from non-food items such as cars left running in garages adjacent to homes. The Centers for Disease Control and Prevention reports that every year, several thousand people go to the hospital emergency room for carbon monoxide poisoning.
Presence in the blood
Carbon monoxide is absorbed through breathing and enters the bloodstream through gas exchange in the lungs. It is also produced during the metabolism of hemoglobin and enters the blood from tissues, and thus is present in all normal tissues, even if it is not inhaled into the body. Normal levels of carbon monoxide circulating in the blood are between 0% and 3%, and are higher in smokers. Carbon monoxide levels cannot be assessed through a physical examination. Laboratory tests require a blood sample (arterial or venous) and laboratory analysis on a CO oximeter. In addition, non-invasive carboxyhemoglobin (SPCO) with pulsed CO oximetry is more effective than invasive methods.
Astrophysics
Outside the Earth, carbon monoxide is the second most abundant molecule in the interstellar medium, after molecular hydrogen. Due to its asymmetry, the carbon monoxide molecule produces much brighter spectral lines than the hydrogen molecule, making CO much easier to detect. Interstellar CO was first detected by radio telescopes in 1970. It is currently the most commonly used tracer of molecular gas in the interstellar medium of galaxies, and molecular hydrogen can only be detected using ultraviolet light, requiring space telescopes. Carbon monoxide observations provide most information about the molecular clouds in which most stars form. Beta Pictoris, the second brightest star in the constellation Pictor, is showing an abundance of infrared radiation compared to normal stars of its type, due to the large amount of dust and gas (including carbon monoxide) near the star.
Production
Many methods have been developed to produce carbon monoxide.
industrial production
The main industrial source of CO is producer gas, a mixture containing mainly carbon monoxide and nitrogen, formed when carbon is burned in air at high temperature when there is an excess of carbon. In the oven, air is forced through a layer of coke. Initially produced CO2 is balanced with the remaining hot coal to produce CO. The reaction of CO2 with carbon to produce CO is described as the Boudouard reaction. Above 800°C, CO is the dominant product:
CO2 + C → 2 CO (ΔH = 170 kJ/mol)
Another source is "water gas", a mixture of hydrogen and carbon monoxide produced by an endothermic reaction of steam and carbon:
H2O + C → H2 + CO (ΔH = +131 kJ/mol)
Other similar "syngas" can be obtained from natural gas and other fuels. Carbon monoxide is also a by-product of the reduction of metal oxide ores with carbon:
MO + C → M + CO
Carbon monoxide is also produced by the direct oxidation of carbon in a limited amount of oxygen or air.
2C (s) + O 2 → 2CO (g)
Since CO is a gas, the reduction process can be controlled by heating, using the positive (favorable) entropy of the reaction. The Ellingham diagram shows that CO production is favored over CO2 at high temperatures.
Preparation in the laboratory
Carbon monoxide is conveniently obtained in the laboratory by dehydration of formic acid or oxalic acid, for example, with concentrated sulfuric acid. Another way is to heat a homogeneous mixture of powdered zinc metal and calcium carbonate, which releases CO and leaves zinc oxide and calcium oxide:
Zn + CaCO3 → ZnO + CaO + CO
Silver nitrate and iodoform also give carbon monoxide:
CHI3 + 3AgNO3 + H2O → 3HNO3 + CO + 3AgI
coordination chemistry
Most metals form coordination complexes containing covalently attached carbon monoxide. Only metals in lower degrees oxidation will combine with carbon monoxide ligands. This is because sufficient electron density is needed to facilitate reverse donation from the metallic DXZ orbital, to the π* molecular orbital from CO. The lone pair on the carbon atom in CO also donates electron density in dx²-y² on the metal to form a sigma bond. This electron donation is also manifested by the cis effect, or labilization of CO ligands in the cis position. Nickel carbonyl, for example, is formed by the direct combination of carbon monoxide and metallic nickel:
Ni + 4 CO → Ni(CO) 4 (1 bar, 55 °C)
For this reason, the nickel in the tube or part of it must not come into prolonged contact with carbon monoxide. Nickel carbonyl easily decomposes back to Ni and CO on contact with hot surfaces, and this method is used to industrial cleaning 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 made by decarbonylation of organic solvents rather than from CO. For example, iridium trichloride and triphenylphosphine react in refluxing 2-methoxyethanol or DMF to give IrCl(CO)(PPh3)2. Metal carbonyls in coordination chemistry are usually studied using infrared spectroscopy.
Organic chemistry and chemistry of the main groups of elements
In the presence of strong acids and water, carbon monoxide reacts with alkenes to form carboxylic acids in a process known as the Koch-Haaf reaction. In the Guttermann-Koch reaction, arenes are converted to benzaldehyde derivatives in the presence of AlCl3 and HCl. Organolithium compounds (such as butyllithium) react with carbon monoxide, but these reactions have little scientific application. Although CO reacts with carbocations and carbanions, it is relatively unreactive with organic compounds without the intervention of metal catalysts. With reagents from the main group, CO undergoes several remarkable reactions. Chlorination of CO is an industrial process that produces 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 C-C connections. The compounds cyclohexahehexone or triquinoyl (C6O6) and cyclopentanepentone or leuconic acid (C5O5), which have so far only been obtained in trace amounts, can be regarded as polymers of carbon monoxide. At pressures above 5 GPa, carbon monoxide is converted into a solid polymer of carbon and oxygen. It is metastable at atmospheric pressure, but it is a powerful explosive.
Usage
Chemical industry
Carbon monoxide is an industrial gas that has many applications in the production of bulk chemical substances. Large amounts of aldehydes are obtained by the reaction of hydroformylation of alkenes, carbon monoxide and H2. Hydroformylation in the Shell process makes it possible to create detergent precursors. Phosgene, suitable for producing isocyanates, polycarbonates and polyurethanes, is produced by passing purified carbon monoxide and chlorine gas through a bed of porous activated carbon which serves as a catalyst. World production of this compound in 1989 was estimated at 2.74 million tons.
CO + Cl2 → COCl2
Methanol is produced by the hydrogenation of carbon monoxide. In a related reaction, the hydrogenation of carbon monoxide involves the formation of a C-C bond, as in the Fischer-Tropsch process, where carbon monoxide is hydrogenated to liquid hydrocarbon fuels. This technology allows coal or biomass to be converted into diesel fuel. In the Monsanto process, carbon monoxide and methanol react in the presence of a rhodium-based catalyst and homogeneous hydroiodic acid to form acetic acid. This process is responsible for most industrial production acetic acid. AT industrial scale, pure carbon monoxide is used to purify nickel in the Mond process.
meat coloring
Carbon monoxide is used in modified atmospheric packaging systems in the United States, primarily in fresh meat products such as beef, pork and fish, to maintain their fresh appearance. Carbon monoxide combines with myoglobin to form carboxymyoglobin, a bright cherry red pigment. Carboxymyoglobin is more stable than the oxidized form of myoglobin, oxymyoglobin, which can oxidize to the brown pigment metmyoglobin. This stable red color can last much longer than regular packaged meat. Typical carbon monoxide levels used in plants using this process are 0.4% to 0.5%. This technology was first recognized as "generally safe" (GRAS) by the US Food and Drug Administration (FDA) in 2002 for use as a secondary packaging system, and does not require labelling. In 2004, the FDA approved CO as the primary packaging method, stating that CO does not mask the smell of spoilage. Despite this decision, it remains controversial issue about whether this method masks food spoilage. In 2007, a bill was proposed in the US House of Representatives to call the modified packaging process using carbon monoxide a color additive, but the bill was not passed. This packaging process is banned in many other countries, including Japan, Singapore, and countries in the European Union.
The medicine
In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on heme from the breakdown of hemoglobin. This process produces a certain amount of carboxyhemoglobin in normal people, even if they do not inhale carbon monoxide. Since the first report that carbon monoxide was a normal neurotransmitter in 1993, as well as one of three gases that naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has received a great deal of clinical attention as a biological regulator. . In many tissues, all three gases are known to act as anti-inflammatory agents, vasodilators, and neovascular growth enhancers. However, these issues are complex because neovascular growth is not always beneficial, as it plays a role in tumor growth as well as in the development of wet macular degeneration, a disease whose risk is increased 4 to 6-fold by smoking (a major source of carbon monoxide). in the blood, several times more than natural production). There is a theory that in some nerve cell synapses, when long-term memories are stored, the receiving cell produces carbon monoxide, which is passed back to the transmitting chamber, causing it to be transmitted more easily in the future. Some of these nerve cells have been shown to contain guanylate cyclase, an enzyme that is activated by carbon monoxide. Many laboratories around the world have conducted studies involving carbon monoxide regarding its anti-inflammatory and cytoprotective properties. These properties can be used to prevent the development of a number of pathological conditions, including ischemic reperfusion injury, transplant rejection, atherosclerosis, severe sepsis, severe malaria, or autoimmune diseases. Human clinical trials have been conducted, but the results have not yet been released.
Carbon 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 the 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. Bottom part luminous flame - this color is given to it by hot particles of carbon (a product of incomplete combustion of wood). From above, the flame is surrounded by a blue-violet border. This burns carbon monoxide formed during the oxidation of wood.
a complex compound of iron - the blood heme (associated with the glo-bin protein), disrupting the functions of oxygen transfer and consumption by tissues. In addition, it enters into an irreversible interaction with some enzymes involved in the energy metabolism of the cell. At a concentration of carbon monoxide in a room of 880 mg / m 3, death occurs after a few hours, and at 10 g / m 3 - almost instantly. The maximum permissible content of carbon monoxide in the air is 20 mg / m 3. The first signs of CO poisoning (at a concentration of 6-30 mg / m 3) are a decrease in the sensitivity of vision and hearing, headache, and a change in heart rate. If a person has poisoned himself with carbon monoxide, he must be taken to fresh air, artificial respiration, in mild cases of poisoning - give strong tea or coffee.
Large amounts of carbon monoxide ( II ) enter the atmosphere as a result of human activity. 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.
When CO reacts with chlorine, 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. Especially great importance has a methanol synthesis reaction: 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.
