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Carbon monoxide
Carbon monoxide, chemical formula CO, is a colorless, odorless, tasteless, flammable and highly toxic gas. It is a major product of the incomplete combustionof carbonand carbon-containing compounds. It is less dense than airunder ordinary conditions, however it accumulates on the ground, meaning that if poisoning causes loss of consciousness the amount of carbon monoxide inhaled increases and so fatality is radically increased. It is very slightly soluble in waterand burns in air with a characteristic blue flame, producing carbon dioxide; it is a component of producer gas and water gas, which are widely used artificial fuels. It is a reducing agent, removing oxygenfrom many compounds and is used in the reduction of metals, e.g., iron, from their ores. At high pressures and elevated temperatures it reacts with hydrogenin the presence of a catalystto form methanol. Carbon monoxide is formed by combustion of carbon in oxygen at high temperatures when there is an excess of carbon. It is also formed with a byproduct oxygen by decomposition of carbon dioxide at very high temperatures (above 2,000 °C). It is present in the exhaust of internal-combustion engines, often the exhaust of automobiles, and is generated in coal stoves, furnaces, and gas appliances that do not get enough air. This may be due to insufficient ventilationor other reasons.
Polluting effectCarbon monoxide from automobile and industrial emissions is a dangerous pollutant that may contribute to the greenhouse effectand global warming. In urban areas carbon monoxide, along with aldehydes, reacts photochemically to produce peroxy radicals. Peroxy radicals react with nitrogen oxideto increase the ratio of NO2 to NO, which reduces the quantity of NO that is available to react with ozone. Carbon monoxide is also a constituent of tobacco smoke. Toxicity
Carbon monoxide is very dangerous and life-threatening to humansand most forms of life, as inhaling excessively high amounts of it will lead to hypoxic injury, neurological damage, and possibly death. A concentration of as little as 0.04% (400 parts per million) carbon monoxide in the air can be fatal. The gas is especially dangerous because it is not easily detected by human senses. Early symptoms of carbon monoxide poisoning include drowsiness and headache, followed by unconsciousness, respiratory failure, and death. First aid for a victim of carbon monoxide poisoning requires access to fresh air; administration of artificial respiration and, if available, oxygen; and, as soon as possible, expert medical attention. When carbon monoxide is inhaled, it reacts with hemoglobin, the red blood pigment that normally carries oxygen to all parts of the body. Because carbon monoxide is attracted to the hemoglobin about 210 times as strongly as is oxygen, it takes the place of oxygen in the blood, causing oxygen starvationthroughout the body. Carbon monoxide detectors for homes are now readily available. The effects of carbon monoxide in parts per million are listed below:
In addition, a recent report concludes that carbon monoxide exposure can lead to significant loss of lifespanafter exposure due to damage to heart muscle. [1] HistoryCarbon monoxide was first prepared by the Frenchchemistde Lassone in 1776by heating zincoxide with cokebut thought it to be hydrogenby mistake as it burned with a blueflame. It was identified as a compound containing carbonand oxygenby the English chemist William Cruikshankin the year 1800. The toxic properties of CO were first thoroughly investigated by the French physiologist Claude Bernardaround 1846. He poisoned dogs with the gas, and noticed that their blood was more rutilant in all the vessels. 'Rutilant' is a French word, but also has an entry in English dictionaries, meaning ruddy, shimmering, or golden. However, it was translated at the time as crimson, scarlet, and now is famously known as 'cherry pink'. During World War Two, carbon monoxide was used to keep motor vehiclesrunning in parts of the world where gasolinewas scarce. External charcoal or wood burners were fitted, and the carbon monoxide produced by gasificationwas piped to the carburetor. ChemistryThe structure of the CO molecule is best described using molecular orbitaltheory. The length of the bond(0.111 nm) indicates that it has a partial triple bond character. The molecule has a small dipole momentand is often represented by three resonance structures:
Note that the octet ruleis violated for the carbon atom in the two structures on the right. The metalnickelforms a volatile compound with carbon monoxide, known as nickel carbonyl. The carbonyl decomposes readily back to the metal and gas, and this was used as the basis for the industrial purification of nickel. Many other metals may form carbonyl complexes containing covalently attached carbon monoxide, these can be made by a range of different methods for instance boiling rutheniumtrichloride with triphenyl phosphinein methoxyethanol (or DMF) the complex [RuHCl(CO)(PPh3)3] can be obtained. Nickel carbonylis special as it can be formed by the direct combination of carbon monoxide and nickelmetal at room temperature. As in nickel carbonyl and other carbonyls, the electron pair on the carbon bonded to the metal. In this case carbon monoxide is regarded as a carbonyl ligand. Carbon monoxide and methanolare reacted together using a homogeneous rhodiumcatalystto form acetic acidin the Monsanto process, which is responsible for most of the industrial production of acetic acid. The CAS registry numberof carbon monoxide is 630-08-0. Carbon monoxide in the atmosphereImage:Mopitt first year carbon monoxide.jpg Carbon monoxide, though thought of as a pollutant today, has always been present in the atmosphere, chiefly as a product of volcanic activity. It occurs dissolved in molten volcanic rock at high pressuresin the earth's mantle. Carbon monoxide contents of volcanic gases vary from less than 0.01 percent to as much as 2 percent depending on the volcano. It also occurs naturally in bushfires. Because natural sources of carbon monoxide are so variable from year to year, it is extremely difficult to accurately measure natural emissions of the gas. Carbon monoxide has an indirect radiative forcing effect by elevating concentrations of methaneand troposphericozonethrough chemical reactions with other atmospheric constituents (e.g., the hydroxyl radical, OH) that would otherwise destroy them. Carbon monoxide is created when carbon-containing fuels are burned incompletely. Through natural processes in the atmosphere, it is eventually oxidized to carbon dioxide. Carbon monoxide concentrations are both short-lived in the atmosphere and spatially variable. See also
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cs:Oxid uhelnatý da:Kulmonoxid de:Kohlenstoffmonoxid es:Monóxido de carbono eo:Karbona monooksido fr:Monoxyde de carbone gl:Monóxido de carbono ko:??? ?? id:Karbon monoksida it:Monossido di carbonio he:???? ?? ????? nl:Koolmonoxide ja:????? no:Karbonmonoksid nn:Karbonmonoksid pl:Tlenek w?gla pt:Monóxido de carbono ru:????????? ???????? sk:Oxid uho?natý fi:Hiilimonoksidi sv:Kolmonoxid vi:Mônôxít cacbon tr:Karbonmonoksit zh:???? Categories: Oxides| Inorganic carbon compounds| Pollutants| Smog| Toxicology| Gases
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