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42-437: The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl , e.g. nickel carbonyl ). The remainder of this article concerns itself with the organic chemistry definition of carbonyl, such that carbon and oxygen share a double bond. In organic chemistry, a carbonyl group characterizes the following types of compounds: Other organic carbonyls are urea and

84-408: A carbonate as byproduct: Thermal combustion is the most common source for carbon monoxide. Carbon monoxide is produced from the partial oxidation of carbon -containing compounds; it forms when there is not enough oxygen to produce carbon dioxide (CO 2 ), such as when operating a stove or an internal combustion engine in an enclosed space. A large quantity of CO byproduct is formed during

126-487: A carbon monoxide presence. Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. Acute exposure can also lead to long-term neurological effects such as cognitive and behavioural changes. Severe CO poisoning may lead to unconsciousness, coma and death. Chronic exposure to low concentrations of carbon monoxide may lead to lethargy, headaches, nausea, flu-like symptoms and neuropsychological and cardiovascular issues. Carbon monoxide has

168-406: A dative or dipolar bond . This causes 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 are each occupied by one electron from carbon and one from oxygen, forming (polar) covalent bonds with a reverse C→O polarization since oxygen is more electronegative than carbon. In the free carbon monoxide molecule,

210-417: A full bond. Thus, in valence bond terms, C≡O is the most important structure, while :C=O is non-octet, but has a neutral formal charge on each atom and represents the second most important resonance contributor. Because of the lone pair and divalence of carbon in this resonance structure, carbon monoxide is often considered to be an extraordinarily stabilized carbene . Isocyanides are compounds in which

252-548: A ligand, CO binds through carbon, forming a kind of triple bond. The lone pair on the carbon atom donates electron density to form a M-CO sigma bond . The two π* orbitals on CO bind to filled metal orbitals. The effect is related to the Dewar-Chatt-Duncanson model . The effects of the quasi-triple M-C bond is reflected in the infrared spectrum of these complexes. Whereas free CO vibrates at 2143 cm-1, its complexes tend to absorb near 1950 cm-1. [REDACTED] In

294-540: A mixture of an organometallic compound, potassium acetylenediolate 2 K · C 2 O 2 , potassium benzenehexolate 6 K C 6 O 6 , and potassium rhodizonate 2 K · C 6 O 6 . The compounds cyclohexanehexone or triquinoyl (C 6 O 6 ) and cyclopentanepentone or leuconic acid (C 5 O 5 ), which so far have been obtained only in trace amounts, can be regarded as polymers of carbon monoxide. At pressures exceeding 5 GPa , carbon monoxide converts to polycarbonyl ,

336-417: A net negative charge δ remains at the carbon end and the molecule has a small dipole moment of 0.122  D . The molecule is therefore asymmetric: oxygen is more electron dense than carbon and is also slightly positively charged compared to carbon being negative. Carbon monoxide has a computed fractional bond order of 2.6, indicating that the "third" bond is important but constitutes somewhat less than

378-540: A solid polymer that is metastable at atmospheric pressure but is explosive. Carbon monoxide is conveniently produced in the laboratory by the dehydration of formic acid or oxalic acid , for example with concentrated sulfuric acid . Another method is heating an intimate mixture of powdered zinc metal and calcium carbonate , which releases CO and leaves behind zinc oxide and calcium oxide : Silver nitrate and iodoform also afford carbon monoxide: Finally, metal oxalate salts release CO upon heating, leaving

420-515: A study of collagen . Substituents can affect carbonyl groups by addition or subtraction of electron density by means of a sigma bond . Δ H σ values are much greater when the substituents on the carbonyl group are more electronegative than carbon. The polarity of C=O bond also enhances the acidity of any adjacent C-H bonds. Due to the positive charge on carbon and the negative charge on oxygen, carbonyl groups are subject to additions and/or nucleophilic attacks. A variety of nucleophiles attack, breaking

462-431: A total of 10 electrons in the valence shell . Following the octet rule for both carbon and oxygen, the two atoms form a triple bond , with six shared electrons 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 carbon, one bonding orbital is occupied by two electrons from oxygen, forming

SECTION 10

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504-458: A wide range of functions across all disciplines of chemistry. The four premier categories of reactivity involve metal-carbonyl catalysis, radical chemistry, cation and anion chemistries. Most metals form coordination complexes containing covalently attached carbon monoxide. These derivatives, which are called metal carbonyls , tend to be more robust when the metal is in lower oxidation states. For example iron pentacarbonyl (Fe(CO) 5 )

546-467: Is isoelectronic with both cyanide anion CN and molecular nitrogen N 2 . Carbon monoxide is the simplest oxocarbon and is isoelectronic with other triply bonded diatomic species possessing 10 valence electrons, including the cyanide anion, the nitrosonium cation, boron monofluoride and molecular nitrogen . It has a molar mass of 28.0, which, according to the ideal gas law , makes it slightly less dense than air, whose average molar mass

588-670: Is 28.8. The carbon and oxygen are connected by a triple bond that consists of a net two pi bonds and one sigma bond . 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 (N 2 ), which has a similar bond length (109.76 pm) and nearly the same molecular mass . Carbon–oxygen double bonds are significantly longer, 120.8 pm in formaldehyde , for example. The boiling point (82 K) and melting point (68 K) are very similar to those of N 2 (77 K and 63 K, respectively). The bond-dissociation energy of 1072 kJ/mol

630-430: Is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond . It is the simplest carbon oxide . In coordination complexes , the carbon monoxide ligand is called carbonyl . It is a key ingredient in many processes in industrial chemistry. The most common source of carbon monoxide

672-551: Is an air-stable, distillable liquid. Nickel carbonyl is an example of a metal carbonyl complex that forms by the direct combination of carbon monoxide with the metal: C. Elschenbroich (2006). Organometallics . VCH. ISBN   978-3-527-29390-2 . These volatile complexes are often highly toxic. Some metal–CO complexes are prepared by decarbonylation of organic solvents, not from CO. For instance, iridium trichloride and triphenylphosphine react in boiling 2-methoxyethanol or DMF to afford IrCl(CO)(PPh 3 ) 2 . As

714-488: Is formed during the formation of NO 2 , the balance of the sequence of chemical reactions starting with carbon monoxide and leading to the formation of ozone is: (where hν refers to the photon of light absorbed by the NO 2 molecule in the sequence) Although the creation of NO 2 is the critical step leading to low level ozone formation, it also increases this ozone in another, somewhat mutually exclusive way, by reducing

756-670: Is high enough (for instance in an underground sea), formic acid will be formed: These reactions can take place in a few million years even at temperatures such as found on Pluto. Carbon monoxide is a temporary atmospheric pollutant in some urban areas, chiefly from the exhaust of internal combustion engines (including vehicles, portable and back-up generators, lawnmowers, power washers, etc.), but also from incomplete combustion of various other fuels (including wood, coal, charcoal, oil, paraffin, propane, natural gas, and trash). Large CO pollution events can be observed from space over cities. Carbon monoxide is, along with aldehydes , part of

798-608: Is passed through a bed of coke . The initially produced CO 2 equilibrates with the remaining hot carbon to give CO. The reaction of CO 2 with carbon to give CO is described as the Boudouard reaction . Above 800 °C, CO is the predominant product: Another source is " water gas ", a mixture of hydrogen and carbon monoxide produced via the endothermic reaction of steam and carbon: Other similar " synthesis gases " can be obtained from natural gas and other fuels. Flue Too Many Requests If you report this error to

840-525: Is present in small amounts (about 80 ppb ) in the Earth's atmosphere . Most of the rest comes from chemical reactions with organic compounds emitted by human activities and natural origins due to photochemical reactions in the troposphere that generate about 5 × 10 kilograms per year. Other natural sources of CO include volcanoes, forest and bushfires , and other miscellaneous forms of combustion such as fossil fuels . Small amounts are also emitted from

882-499: Is stronger than that of N 2 (942 kJ/mol) and represents the strongest chemical bond known. The ground electronic state of carbon monoxide is a singlet state since there are no unpaired electrons. The strength of the C-O bond in carbon monoxide is indicated by the high frequency of its vibration, 2143 cm . For comparison, organic carbonyls such as ketones and esters absorb at around 1700 cm . Carbon and oxygen together have

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924-445: Is the most common type of fatal air poisoning in many countries. Carbon monoxide has important biological roles across phylogenetic kingdoms. It is produced by many organisms, including humans. In mammalian physiology, carbon monoxide is a classical example of hormesis where low concentrations serve as an endogenous neurotransmitter ( gasotransmitter ) and high concentrations are toxic resulting in carbon monoxide poisoning . It

966-731: Is the partial combustion of carbon-containing compounds. Numerous environmental and biological sources generate carbon monoxide. In industry, carbon monoxide is important in the production of many compounds, including drugs, fragrances, and fuels. Upon emission into the atmosphere, carbon monoxide affects several processes that contribute to climate change . Indoors CO is one of the most acutely toxic contaminants affecting indoor air quality . CO may be emitted from tobacco smoke and generated from malfunctioning fuel burning stoves (wood, kerosene, natural gas, propane) and fuel burning heating systems (wood, oil, natural gas) and from blocked flues connected to these appliances. Carbon monoxide poisoning

1008-575: Is the second-most common diatomic molecule in the interstellar medium , after molecular hydrogen . Because of its asymmetry, this polar molecule produces far brighter spectral lines than the hydrogen molecule, making CO much easier to detect. Interstellar CO was first detected with radio telescopes in 1970. It is now the most commonly used tracer of molecular gas in general in the interstellar medium of galaxies, as molecular hydrogen can only be detected using ultraviolet light, which requires space telescopes . Carbon monoxide observations provide much of

1050-412: Is very little CO in the atmosphere of Pluto , which seems to have been formed from comets. This may be because there is (or was) liquid water inside Pluto. Carbon monoxide can react with water to form carbon dioxide and hydrogen: This is called the water-gas shift reaction when occurring in the gas phase, but it can also take place (very slowly) in an aqueous solution. If the hydrogen partial pressure

1092-409: The carbamates , the derivatives of acyl chlorides chloroformates and phosgene , carbonate esters , thioesters , lactones , lactams , hydroxamates , and isocyanates . Examples of inorganic carbonyl compounds are carbon dioxide and carbonyl sulfide . A special group of carbonyl compounds are dicarbonyl compounds, which can exhibit special properties. For organic compounds, the length of

1134-453: The hydroxyl radical , OH) that would otherwise destroy methane. Through natural processes in the atmosphere, it is oxidized to carbon dioxide and ozone. Carbon monoxide is short-lived in the atmosphere (with an average lifetime of about one to two months), and spatially variable in concentration. Due to its long lifetime in the mid-troposphere, carbon monoxide is also used as a tracer for pollutant plumes. Beyond Earth, carbon monoxide

1176-410: The "silent killer". It can be found in confined areas of poor ventilation in both surface mines and underground mines. The most common sources of carbon monoxide in mining operations are the internal combustion engine and explosives; however, in coal mines, carbon monoxide can also be found due to the low-temperature oxidation of coal. The idiom " Canary in the coal mine " pertained to an early warning of

1218-498: The C-O bond does not vary widely from 120 picometers . Inorganic carbonyls have shorter C-O distances: CO , 113; CO 2 , 116; and COCl 2 , 116 pm. The carbonyl carbon is typically electrophilic . A qualitative order of electrophilicity is RCHO (aldehydes) > R 2 CO (ketones) > RCO 2 R' (esters) > RCONH 2 (amides). A variety of nucleophiles attack, breaking the carbon-oxygen double bond . Interactions between carbonyl groups and other substituents were found in

1260-428: The O is replaced by an NR (R = alkyl or aryl) group and have a similar bonding scheme. If carbon monoxide acts as a ligand , the polarity of the dipole may reverse with a net negative charge on the oxygen end, depending on the structure of the coordination complex . See also the section "Coordination chemistry" below. Theoretical and experimental studies show that, despite the greater electronegativity of oxygen,

1302-404: The carbon-oxygen double bond , and leading to addition-elimination reactions . Nucleophiliic reactivity is often proportional to the basicity of the nucleophile and as nucleophilicity increases, the stability within a carbonyl compound decreases. The pK a values of acetaldehyde and acetone are 16.7 and 19 respectively, Carbon monoxide Carbon monoxide ( chemical formula CO )

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1344-436: The dipole moment points from the more-negative carbon end to the more-positive oxygen end. The three bonds are in fact polar covalent bonds that are strongly polarized. The calculated polarization toward the oxygen atom is 71% for the σ-bond and 77% for both π-bonds . The oxidation state of carbon in carbon monoxide is +2 in each of these structures. It is calculated by counting all the bonding electrons as belonging to

1386-549: The information about the molecular clouds in which most stars form . Beta Pictoris , the second brightest star in the constellation Pictor , shows an excess of infrared emission compared to normal stars of its type, which is caused by large quantities of dust and gas (including carbon monoxide) near the star. In the atmosphere of Venus carbon monoxide occurs as a result of the photodissociation of carbon dioxide by electromagnetic radiation of wavelengths shorter than 169 nm . It has also been identified spectroscopically on

1428-439: The main sources of indoor CO emission come from cooking and heating devices that burn fossil fuels and are faulty, incorrectly installed or poorly maintained. Appliance malfunction may be due to faulty installation or lack of maintenance and proper use. In low- and middle-income countries the most common sources of CO in homes are burning biomass fuels and cigarette smoke. Miners refer to carbon monoxide as " whitedamp " or

1470-468: The more electronegative oxygen. Only the two non-bonding electrons on carbon are assigned to carbon. In this count, carbon then has only two valence electrons in the molecule compared to four in the free atom. Carbon monoxide occurs in various natural and artificial environments. Photochemical degradation of plant matter for example generates an estimated 60 million tons/year. Typical concentrations in parts per million are as follows: Carbon monoxide (CO)

1512-576: The ocean, and from geological activity because carbon monoxide occurs dissolved in molten volcanic rock at high pressures in the Earth's mantle . Because natural sources of carbon monoxide vary from year to year, it is difficult to accurately measure natural emissions of the gas. Carbon monoxide has an indirect effect on radiative forcing by elevating concentrations of direct greenhouse gases , including methane and tropospheric ozone . CO can react chemically with other atmospheric constituents (primarily

1554-404: The oxidative processes for the production of chemicals. For this reason, the process off-gases have to be purified. Many methods have been developed for carbon monoxide production. A major industrial source of CO is producer gas , a mixture containing mostly carbon monoxide and nitrogen, formed by combustion of carbon in air at high temperature when there is an excess of carbon. In an oven, air

1596-482: The presence of metal catalysts. With main group reagents, CO undergoes several noteworthy reactions. Chlorination of CO is the industrial route to the important compound phosgene . With borane CO forms the adduct H 3 BCO , which is isoelectronic with the acylium cation [H 3 CCO] . CO reacts with sodium to give products resulting from C−C coupling such as sodium acetylenediolate 2 Na · C 2 O 2 . It reacts with molten potassium to give

1638-538: The presence of strong acids, alkenes react with carboxylic acids . Hydrolysis of this species (an acylium ion ) gives the carboxylic acid, a net process known as the Koch–Haaf reaction . In the Gattermann–Koch reaction , arenes are converted to benzaldehyde derivatives in the presence of CO, AlCl 3 , and HCl . A mixture of hydrogen gas and CO reacts with alkenes to give aldehydes. The process requires

1680-418: The quantity of NO that is available to react with ozone. Carbon monoxide is one of the most acutely toxic indoor air contaminants . Carbon monoxide may be emitted from tobacco smoke and generated from malfunctioning fuel burning stoves (wood, kerosene, natural gas, propane) and fuel burning heating systems (wood, oil, natural gas) and from blocked flues connected to these appliances. In developed countries

1722-510: The series of cycles of chemical reactions that form photochemical smog . It reacts with hydroxyl radical ( OH) to produce a radical intermediate HOCO, which rapidly transfers its radical hydrogen to O 2 to form peroxy radical (HO 2 ) and carbon dioxide (CO 2 ). Peroxy radical subsequently reacts with nitrogen oxide (NO) to form nitrogen dioxide (NO 2 ) and hydroxyl radical. NO 2 gives O( P) via photolysis, thereby forming O 3 following reaction with O 2 . Since hydroxyl radical

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1764-433: The surface of Neptune's moon Triton . Solid carbon monoxide is a component of comets . The volatile or "ice" component of Halley's Comet is about 15% CO. At room temperature and at atmospheric pressure, carbon monoxide is actually only metastable (see Boudouard reaction ) and the same is true at low temperatures where CO and CO 2 are solid, but nevertheless it can exist for billions of years in comets. There

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