Béda révisi "Karbon monoksida"

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'''Karbon monoksida''' ([[rumus kimia]]na [[karbon|C]][[oksigén|O]]) nyaéta [[sanyawa kimia]] anu diwangun ku hiji [[atom]] [[karbon]] nu [[beungkeut kimia|meungkeut]] hiji atom [[oksigén]] ku dua [[beungkeut kovalén]] jeung hiji [[beungkeut kovalén koordinat]]. Ieu [[gas]] nu tanpa warna, tanpa bau, jeung tanpa rasa téh mangrupakeunmangrupa sanyawa karbon anorganik. Ieu sanyawa dihasilkeun tina [[durukan]] parsial sanyawaan nu ngandung karbon, utamana dina [[mesin durukan-internal]]. Mun diduruk sampurna, ieu sanyawaan bakal jadi [[karbon dioksida]]. Najan [[toksisitas]]na matak bahya, CO penting pisan pikeun téhnologi modéren salaku prékursor rupa-rupa produk.
 
== Produksi ==
In the presence of strong acids and water, carbon monoxide reacts with [[olefins]] to form [[carboxylic acids]] in a process known as the Koch-Haaf reaction.<ref>{{OrgSynth | author = Koch, H.; Haaf, W. | title = 1-Adamantanecarboxylic Acid | year = 1973 | collvol = 5 | collvolpages = 20 | prep = cv5p0020}}</ref> In the [[Gattermann-Koch reaction]], [[Aromatic hydrocarbon|arenes]] are converted to [[benzaldehyde]] derivatives in the presence of [[aluminium chloride|AlCl<sub>3</sub>]] and [[hydrogen chloride|HCl]].<ref>{{OrgSynth | title = ''p''-Tolualdehyde | author = G. H. Coleman, David Craig | collvol = 2 | collvolpages = 583 | year = 1943 | prep = cv2p0583}}</ref> Organolithium compounds, e.g. [[butyl lithium]] react with CO, but this reaction enjoys little use.
 
Although CO reacts with [[carbocation]]s and [[carbanion]]s, it is relatively unreactive toward organic compounds without the intervention of metal catalysts.<ref>Chatani, N.; Murai, S. "Carbon Monoxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289}}</ref>
 
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 an adduct, H<sub>3</sub>BCO, which is isoelectronic with the [[acylium]] cation [H<sub>3</sub>CCO]<sup>+</sup>. CO reacts with [[sodium]] to give products resulting from C-C coupling such as Na<sub>2</sub>C<sub>2</sub>O<sub>2</sub> (sodium acetylenediolate), and [[potassium]] to give K<sub>2</sub>C<sub>2</sub>O<sub>2</sub> (potassium acetylenediolate) and K<sub>2</sub>C<sub>6</sub>O<sub>6</sub> (potassium rhodizonate).
[[Image:Mopitt first year carbon monoxide.jpg|thumb|240px|[[MOPITT]] 2000 global carbon monoxide ]]
 
Carbon monoxide, though thought of as a pollutant today, has always been present in the atmosphere, chiefly as a product of [[volcano|volcanic activity]]. It occurs dissolved in molten volcanic rock at high [[pressure]]s in the earth's [[mantle (geology)|mantle]]. Carbon monoxide contents of volcanic gases vary from less than 0.01% to as much as 2% depending on the volcano. It also occurs naturally in [[bushfire]]s. 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 [[methane]] and [[troposphere|tropospheric]] [[ozone]] through chemical reactions with other atmospheric constituents (e.g., the [[hydroxyl]] [[Radical (chemistry)|radical]], OH<sup>'''.'''</sup>) that would otherwise destroy them. 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.
Carbon monoxide is used in [[modified atmosphere]] packaging systems in the US, mainly with fresh meat products such as beef and pork. The CO combines with [[myoglobin]] to form carboxymyoglobin, a bright cherry red pigment. Carboxymyoglobin is more stable than the oxygenated form of myoglobin, oxymyoglobin, which can become oxidized to the brown pigment, metmyoglobin. This stable red colour can persist much longer than in normally packaged meat, giving the appearance of freshness.<ref name="Meatsci1999_SORHEIM">{{cite journal | author=Sorheim, S, Nissena, H, Nesbakken, T | title=The storage life of beef and pork packaged in an atmosphere with low carbon monoxide and high carbon dioxide | journal=Journal of Meat Science | year=1999 | pages=157–64 | volume=52 | issue=2 | doi = 10.1016/S0309-1740(98)00163-6}}</ref> Typical levels of CO used are 0.4% to 0.5%.
 
The technology was first given [[generally recognized as safe]] status by the [[FDA]] in 2002 for use as a secondary packaging system. In 2004 the FDA approved CO as primary packaging method, declaring that CO does not mask spoilage odour.<ref name="Meatsci2005_eilert">{{cite journal | author=Eilert EJ | title=New packaging technologies for the 21st century | journal=Journal of Meat Science | year=2005 | pages=122–27 | volume=71 | issue=1 | doi = 10.1016/j.meatsci.2005.04.003}}</ref> Despite this ruling, the technology remains controversial in the US for fears that it is deceptive and masks spoilage.<ref>{{cite news | url = http://www.foodsafetymagazine.com/article.asp?id=644&sub=sub1 | title = Low-Oxygen Packaging with CO: A Study in Food Politics That Warrants Peer Review| accessdate = 2007-04-18}}</ref>
 
One reaction in the body produces CO. Carbon monoxide is produced naturally as a breakdown of [[heme]] (which is one of [[hemoglobin]] moieties), a substrate for the enzyme [[heme oxygenase]]. The enzymatic reaction results in breakdown of heme to CO, biliverdin and Fe<sup>3+</sup> radical. The endogenously produced CO may have important physiological roles in the body (eg as a [[neurotransmitter]] or a blood vessels relaxant). In addition CO regulates inflammatory reactions in a manner that prevents the development of several diseases such as atherosclerosis or severe malaria.
 
CO is a nutrient for [[methanogen]]ic bacteria,<ref>{{cite journal | author = R. K. Thauer | title = Biochemistry of methanogenesis: a tribute to Marjory Stephenson. 1998 Marjory Stephenson Prize Lecture | year = 1998 | journal = [[Microbiology]] | volume = 144 | issue = 9 | pages = 2377–2406 | url = http://mic.sgmjournals.org/cgi/reprint/144/9/2377 | format = Free}}</ref> a building block for acetyl[[coenzyme A]]. This theme is the subject for the emerging field of [[bioorganometallic chemistry]]. In bacteria, CO is produced via the reduction of carbon dioxide via the enzyme carbon monoxide dehydrogenase, an Fe-Ni-S-containing protein.<ref>{{cite book | title = Bioorganometallics: Biomolecules, Labeling, Medicine | author = Jaouen, G., Ed. | publisher = Wiley-VCH | location = Weinheim | year = 2006 | isbn = 3-527-30990-X}}</ref>
 
A haeme-based CO-sensor protein, CooA, is known.<ref>{{cite journal | author = Roberts, G. P.; Youn, H.; Kerby, R. L. | title = CO-Sensing Mechanisms | journal = Microbiology and Molecular Biology Reviews | year = 2004 | volume = 68 | pages = 453–473 | doi = 10.1128/MMBR.68.3.453-473.2004 | pmid = 15353565}}</ref> The scope of its biological role is still unclear, it is apparently part of a signaling pathway in bacteria and archaea, but its occurrence in mammals is not established.
==Toxicity==
{{main|Carbon monoxide poisoning}}
Carbon monoxide is a significantly toxic gas and has no odor or color. It is the most common type of fatal poisoning in many countries.<ref name="Toxicology2002-omaye">{{cite journal | author=Omaye ST. | title=Metabolic modulation of carbon monoxide toxicity | journal=Toxicology | year=2002 | pages=139–50 | volume=180 | issue=2 | doi = 10.1016/S0300-483X(02)00387-6}}</ref> Exposures can lead to significant toxicity of the [[central nervous system]] and [[heart]]. Following poisoning, long-term [[sequela]]e often occur. Carbon monoxide can also have severe effects on the [[baby]] of a pregnant woman. Symptoms of mild poisoning include headaches and dizziness at concentrations less than 100 ppm. Concentrations as low as 667 ppm can cause up to 50% of the body's haemoglobin to be converted to [[Carboxyhaemoglobin|carboxy-haemoglobin (HbCO)]]. Carboxy-haemoglobin is quite stable but this change is reversible. Carboxy-haemoglobin is ineffective for delivering oxygen, resulting in some body parts not receiving oxygen needed. As a result, exposures of this level can be life-threatening. In the United States, [[Occupational Safety and Health Administration|OSHA]] limits long-term workplace exposure levels to 50 ppm.
 
The mechanisms by which carbon monoxide produces toxic effects are not yet fully understood, but [[haemoglobin]], [[myoglobin]], and mitochondrial [[cytochrome oxidase]] are thought to be compromised. Treatment largely consists of administering 100% [[oxygen]] or [[hyperbaric oxygen]] therapy, although the optimum treatment remains controversial.<ref name="ToxicolRev2005-buckley">{{cite journal | author=Buckley NA, Isbister GK, Stokes B, Juurlink DN. | title=Hyperbaric oxygen for carbon monoxide poisoning : a systematic review and critical analysis of the evidence | journal=Toxicol Rev | year=2005 | pages=75–92 | volume=24 | issue=2 | pmid = 16180928 | url=http://toxicology.adisonline.com/pt/re/tox/abstract.00139709-200524020-00002.htm | format = Abstract}}</ref> Domestic carbon monoxide poisoning can be prevented by the use of household [[carbon monoxide detector]]s.
* [http://www.carbonmonoxide.net Carbon Monoxide Network & Forum]
* [http://mattson.creighton.edu/CO/index.html Microscale Gas Chemistry Experiments with Carbon Monoxide]
* ResearchReséarch on the therapeutic effects of CO [http://www.igc.gulbenkian.pt/research/unit/43 (Gulbenkian Science Institute)]
* [http://www.rsc.org/Publishing/Journals/cb/Volume/2007/11/Dont_blame_the_messenger.asp Instant insight] pedaran fisiologi karbon monoksida ti [[Royal Society of Chemistry]]
 
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