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90-1022: Halon may refer to: Haloalkane , or halogenoalkane, a group of chemical compounds consisting of alkanes with linked halogens (in particular, bromine-containing haloalkanes) Halomethane compounds: Halon 10001 (iodomethane) Halon 1001 (bromomethane) Halon 1011 (bromochloromethane, CH 2 BrCl) Halon 104 (carbon tetrachloride) Halon 1103 (tribromofluoromethane) Halon 112 (dichlorofluoromethane) Halon 1201 (bromodifluoromethane) Halon 1202 (dibromodifluoromethane) Halon 1211 (bromochlorodifluoromethane, CF 2 ClBr) Halon 122 (dichlorodifluoromethane) Halon 1301 (bromotrifluoromethane, CBrF 3 ) Halon 14 (tetrafluoromethane) Halon 2011B (1-bromo-2-chloroethane) Halon 2301 (1,1,1-trifluoro-2-bromoethane) Halon 2311 (1,1,1-trifluoro-2,2-chlorobromoethane, halothane) Halon 242 (1,2-dichlorotetrafluoroethane) Halon 2402 (dibromotetrafluoroethane, C 2 Br 2 F 4 )—used as

180-567: A covalent bond between the two. Thus C–X is broken by heterolytic fission resulting in a halide ion, X . As can be seen, the OH is now attached to the alkyl group, creating an alcohol . (Hydrolysis of bromoethane, for example, yields ethanol ). Reactions with ammonia give primary amines. Chloro- and bromoalkanes are readily substituted by iodide in the Finkelstein reaction . The iodoalkanes produced easily undergo further reaction. Sodium iodide

270-730: A hexagonal crystal lattice with all atoms covalently bonded and properties similar to those of diamond. Fullerenes are a synthetic crystalline formation with a graphite-like structure, but in place of flat hexagonal cells only, some of the cells of which fullerenes are formed may be pentagons, nonplanar hexagons, or even heptagons of carbon atoms. The sheets are thus warped into spheres, ellipses, or cylinders. The properties of fullerenes (split into buckyballs, buckytubes, and nanobuds) have not yet been fully analyzed and represent an intense area of research in nanomaterials . The names fullerene and buckyball are given after Richard Buckminster Fuller , popularizer of geodesic domes , which resemble

360-405: A hydrohalic acid rarely gives a pure product, instead generating ethers . However, some exceptions are known: ionic liquids suppress the formation or promote the cleavage of ethers, hydrochloric acid converts tertiary alcohols to choloroalkanes, and primary and secondary alcohols convert similarly in the presence of a Lewis acid activator, such as zinc chloride . The latter is exploited in

450-706: A nuclear halo , which means its radius is appreciably larger than would be expected if the nucleus were a sphere of constant density. Formation of the carbon atomic nucleus occurs within a giant or supergiant star through the triple-alpha process . This requires a nearly simultaneous collision of three alpha particles (helium nuclei), as the products of further nuclear fusion reactions of helium with hydrogen or another helium nucleus produce lithium-5 and beryllium-8 respectively, both of which are highly unstable and decay almost instantly back into smaller nuclei. The triple-alpha process happens in conditions of temperatures over 100 megakelvins and helium concentration that

540-434: A π-cloud , graphite conducts electricity , but only in the plane of each covalently bonded sheet. This results in a lower bulk electrical conductivity for carbon than for most metals. The delocalization also accounts for the energetic stability of graphite over diamond at room temperature. At very high pressures, carbon forms the more compact allotrope, diamond, having nearly twice the density of graphite. Here, each atom

630-418: A carbon atom with six bonds. More specifically, the dication could be described structurally by the formulation [MeC(η -C 5 Me 5 )] , making it an "organic metallocene " in which a MeC fragment is bonded to a η -C 5 Me 5 fragment through all five of the carbons of the ring. It is important to note that in the cases above, each of the bonds to carbon contain less than two formal electron pairs. Thus,

720-550: A carbon-metal covalent bond (e.g., metal carboxylates) are termed metalorganic compounds. While carbon is understood to strongly prefer formation of four covalent bonds, other exotic bonding schemes are also known. Carboranes are highly stable dodecahedral derivatives of the [B 12 H 12 ] unit, with one BH replaced with a CH . Thus, the carbon is bonded to five boron atoms and one hydrogen atom. The cation [(Ph 3 PAu) 6 C] contains an octahedral carbon bound to six phosphine-gold fragments. This phenomenon has been attributed to

810-462: A density of about 2 kg/m . Similarly, glassy carbon contains a high proportion of closed porosity , but contrary to normal graphite, the graphitic layers are not stacked like pages in a book, but have a more random arrangement. Linear acetylenic carbon has the chemical structure −(C≡C) n − . Carbon in this modification is linear with sp orbital hybridization , and is a polymer with alternating single and triple bonds. This carbyne

900-420: A diatomic halogen molecule. Free radical halogenation typically produces a mixture of compounds mono- or multihalogenated at various positions. In hydrohalogenation , an alkene reacts with a dry hydrogen halide (HX) electrophile like hydrogen chloride ( HCl ) or hydrogen bromide ( HBr ) to form a mono-haloalkane. The double bond of the alkene is replaced by two new bonds, one with the halogen and one with

990-583: A fire extinguisher Halon 2501 (pentafluorobromoethane) Halon 2600 (hexafluoroethane) Halon 4402 (1,1,2,2-tetrafluoro-1,4-dibromobutane) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Halon . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Halon&oldid=1241545615 " Category : Disambiguation pages Hidden categories: Short description

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1080-424: A free-radical mechanism. Alkenes also react with halogens (X 2 ) to form haloalkanes with two neighboring halogen atoms in a halogen addition reaction . Alkynes react similarly, forming the tetrahalo compounds. This is sometimes known as "decolorizing" the halogen, since the reagent X 2 is colored and the product is usually colorless and odorless. Alcohol can be converted to haloalkanes. Direct reaction with

1170-518: A hardness superior to diamonds. In the vapor phase, some of the carbon is in the form of highly reactive diatomic carbon dicarbon ( C 2 ). When excited, this gas glows green. Carbon is the fourth most abundant chemical element in the observable universe by mass after hydrogen, helium, and oxygen. Carbon is abundant in the Sun, stars, comets, and in the atmospheres of most planets. Some meteorites contain microscopic diamonds that were formed when

1260-413: A high activation energy barrier, the transition into graphite is so slow at normal temperature that it is unnoticeable. However, at very high temperatures diamond will turn into graphite, and diamonds can burn up in a house fire. The bottom left corner of the phase diagram for carbon has not been scrutinized experimentally. Although a computational study employing density functional theory methods reached

1350-425: A hydrogen based engine in cars. The amorphous form is an assortment of carbon atoms in a non-crystalline, irregular, glassy state, not held in a crystalline macrostructure. It is present as a powder, and is the main constituent of substances such as charcoal, lampblack (soot), and activated carbon . At normal pressures, carbon takes the form of graphite, in which each atom is bonded trigonally to three others in

1440-435: A lower binding affinity. Cyanide (CN ), has a similar structure, but behaves much like a halide ion ( pseudohalogen ). For example, it can form the nitride cyanogen molecule ((CN) 2 ), similar to diatomic halides. Likewise, the heavier analog of cyanide, cyaphide (CP ), is also considered inorganic, though most simple derivatives are highly unstable. Other uncommon oxides are carbon suboxide ( C 3 O 2 ),

1530-513: A melting point of −183.6 °C. As they contain fewer C–H bonds, haloalkanes are less flammable than alkanes, and some are used in fire extinguishers. Haloalkanes are better solvents than the corresponding alkanes because of their increased polarity. Haloalkanes containing halogens other than fluorine are more reactive than the parent alkanes—it is this reactivity that is the basis of most controversies. Many are alkylating agents , with primary haloalkanes and those containing heavier halogens being

1620-414: A plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons . The resulting network is 2-dimensional, and the resulting flat sheets are stacked and loosely bonded through weak van der Waals forces . This gives graphite its softness and its cleaving properties (the sheets slip easily past one another). Because of the delocalization of one of the outer electrons of each atom to form

1710-526: A small number of stabilized carbocations (three bonds, positive charge), radicals (three bonds, neutral), carbanions (three bonds, negative charge) and carbenes (two bonds, neutral), although these species are much more likely to be encountered as unstable, reactive intermediates. Carbon occurs in all known organic life and is the basis of organic chemistry . When united with hydrogen, it forms various hydrocarbons that are important to industry as refrigerants, lubricants, solvents, as chemical feedstock for

1800-463: A solution of sodium nitrite . Upon heating this solution with copper(I) chloride, the diazonium group is replaced by -Cl. This is a comparatively easy method to make aryl halides as the gaseous product can be separated easily from aryl halide. When an iodide is to be made, copper chloride is not needed. Addition of potassium iodide with gentle shaking produces the haloalkane. Haloalkanes are reactive towards nucleophiles . They are polar molecules:

1890-432: A vast number of compounds , with about two hundred million having been described and indexed; and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions. The allotropes of carbon include graphite , one of the softest known substances, and diamond , the hardest naturally occurring substance. It bonds readily with other small atoms, including other carbon atoms, and

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1980-403: Is a chemical element ; it has symbol C and atomic number 6. It is nonmetallic and tetravalent —meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 electrons. It belongs to group 14 of the periodic table . Carbon makes up about 0.025 percent of Earth's crust. Three isotopes occur naturally, C and C being stable, while C

2070-465: Is a radionuclide , decaying with a half-life of 5,700 years. Carbon is one of the few elements known since antiquity . Carbon is the 15th most abundant element in the Earth's crust , and the fourth most abundant element in the universe by mass after hydrogen , helium , and oxygen . Carbon's abundance, its unique diversity of organic compounds , and its unusual ability to form polymers at

2160-441: Is a two-dimensional sheet of carbon with the atoms arranged in a hexagonal lattice. As of 2009, graphene appears to be the strongest material ever tested. The process of separating it from graphite will require some further technological development before it is economical for industrial processes. If successful, graphene could be used in the construction of a space elevator . It could also be used to safely store hydrogen for use in

2250-439: Is almost constant, but decreases predictably in their bodies after death. This principle is used in radiocarbon dating , invented in 1949, which has been used extensively to determine the age of carbonaceous materials with ages up to about 40,000 years. There are 15 known isotopes of carbon and the shortest-lived of these is C which decays through proton emission and has a half-life of 3.5 × 10 s. The exotic C exhibits

2340-407: Is also found in methane hydrates in polar regions and under the seas. Various estimates put this carbon between 500, 2500, or 3,000 Gt. According to one source, in the period from 1751 to 2008 about 347 gigatonnes of carbon were released as carbon dioxide to the atmosphere from burning of fossil fuels. Another source puts the amount added to the atmosphere for the period since 1750 at 879 Gt, and

2430-415: Is at 10.8 ± 0.2 megapascals (106.6 ± 2.0 atm; 1,566 ± 29 psi) and 4,600 ± 300 K (4,330 ± 300 °C; 7,820 ± 540 °F), so it sublimes at about 3,900 K (3,630 °C; 6,560 °F). Graphite is much more reactive than diamond at standard conditions, despite being more thermodynamically stable, as its delocalised pi system

2520-594: Is bonded tetrahedrally to four others, forming a 3-dimensional network of puckered six-membered rings of atoms. Diamond has the same cubic structure as silicon and germanium , and because of the strength of the carbon-carbon bonds , it is the hardest naturally occurring substance measured by resistance to scratching . Contrary to the popular belief that "diamonds are forever" , they are thermodynamically unstable ( Δ f G ° (diamond, 298 K) = 2.9 kJ/mol ) under normal conditions (298 K, 10  Pa) and should theoretically transform into graphite. But due to

2610-406: Is capable of forming multiple stable covalent bonds with suitable multivalent atoms. Carbon is a component element in the large majority of all chemical compounds , with about two hundred million examples having been described in the published chemical literature. Carbon also has the highest sublimation point of all elements. At atmospheric pressure it has no melting point, as its triple point

2700-553: Is carbon dioxide (CO 2 ). This was once the principal constituent of the paleoatmosphere , but is a minor component of the Earth's atmosphere today. Dissolved in water, it forms carbonic acid ( H 2 CO 3 ), but as most compounds with multiple single-bonded oxygens on a single carbon it is unstable. Through this intermediate, though, resonance-stabilized carbonate ions are produced. Some important minerals are carbonates, notably calcite . Carbon disulfide ( CS 2 )

2790-414: Is different from Wikidata All article disambiguation pages All disambiguation pages Haloalkane Haloalkanes have been known for centuries. Chloroethane was produced in the 15th century. The systematic synthesis of such compounds developed in the 19th century in step with the development of organic chemistry and the understanding of the structure of alkanes. Methods were developed for

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2880-663: Is dissolved in the oceans; if bacteria do not consume it, dead plant or animal matter may become petroleum or coal, which releases carbon when burned. Carbon can form very long chains of interconnecting carbon–carbon bonds , a property that is called catenation . Carbon-carbon bonds are strong and stable. Through catenation, carbon forms a countless number of compounds. A tally of unique compounds shows that more contain carbon than do not. A similar claim can be made for hydrogen because most organic compounds contain hydrogen chemically bonded to carbon or another common element like oxygen or nitrogen. The simplest form of an organic molecule

2970-801: Is found in large quantities in the United States (mostly in New York and Texas ), Russia, Mexico, Greenland, and India. Natural diamonds occur in the rock kimberlite , found in ancient volcanic "necks", or "pipes". Most diamond deposits are in Africa, notably in South Africa, Namibia, Botswana, the Republic of the Congo, and Sierra Leone. Diamond deposits have also been found in Arkansas , Canada,

3060-422: Is found in trace amounts on Earth of 1 part per trillion (0.0000000001%) or more, mostly confined to the atmosphere and superficial deposits, particularly of peat and other organic materials. This isotope decays by 0.158 MeV β emission . Because of its relatively short half-life of 5700 ± 30  years, C is virtually absent in ancient rocks. The amount of C in the atmosphere and in living organisms

3150-462: Is much more vulnerable to attack. For example, graphite can be oxidised by hot concentrated nitric acid at standard conditions to mellitic acid , C 6 (CO 2 H) 6 , which preserves the hexagonal units of graphite while breaking up the larger structure. Carbon sublimes in a carbon arc, which has a temperature of about 5800 K (5,530 °C or 9,980 °F). Thus, irrespective of its allotropic form, carbon remains solid at higher temperatures than

3240-506: Is of considerable interest to nanotechnology as its Young's modulus is 40 times that of the hardest known material – diamond. In 2015, a team at the North Carolina State University announced the development of another allotrope they have dubbed Q-carbon , created by a high-energy low-duration laser pulse on amorphous carbon dust. Q-carbon is reported to exhibit ferromagnetism, fluorescence , and

3330-577: Is one such star system with an abundance of carbon, enabling the existence of life as we know it. It is the opinion of most scholars that all the carbon in the Solar System and the Milky Way comes from dying stars. The CNO cycle is an additional hydrogen fusion mechanism that powers stars, wherein carbon operates as a catalyst. Rotational transitions of various isotopic forms of carbon monoxide (for example, CO, CO, and CO) are detectable in

3420-453: Is similar. Nevertheless, due to its physical properties and its association with organic synthesis, carbon disulfide is sometimes classified as an organic solvent. The other common oxide is carbon monoxide (CO). It is formed by incomplete combustion, and is a colorless, odorless gas. The molecules each contain a triple bond and are fairly polar , resulting in a tendency to bind permanently to hemoglobin molecules, displacing oxygen, which has

3510-566: Is stabilized in various multi-atomic structures with diverse molecular configurations called allotropes . The three relatively well-known allotropes of carbon are amorphous carbon , graphite , and diamond. Once considered exotic, fullerenes are nowadays commonly synthesized and used in research; they include buckyballs , carbon nanotubes , carbon nanobuds and nanofibers . Several other exotic allotropes have also been discovered, such as lonsdaleite , glassy carbon , carbon nanofoam and linear acetylenic carbon (carbyne). Graphene

3600-681: Is the hydrocarbon—a large family of organic molecules that are composed of hydrogen atoms bonded to a chain of carbon atoms. A hydrocarbon backbone can be substituted by other atoms, known as heteroatoms . Common heteroatoms that appear in organic compounds include oxygen, nitrogen, sulfur, phosphorus, and the nonradioactive halogens, as well as the metals lithium and magnesium. Organic compounds containing bonds to metal are known as organometallic compounds ( see below ). Certain groupings of atoms, often including heteroatoms, recur in large numbers of organic compounds. These collections, known as functional groups , confer common reactivity patterns and allow for

3690-760: Is used as a catalyst . Haloalkanes react with ionic nucleophiles (e.g. cyanide , thiocyanate , azide ); the halogen is replaced by the respective group. This is of great synthetic utility: chloroalkanes are often inexpensively available. For example, after undergoing substitution reactions, cyanoalkanes may be hydrolyzed to carboxylic acids, or reduced to primary amines using lithium aluminium hydride . Azoalkanes may be reduced to primary amines by Staudinger reduction or lithium aluminium hydride . Amines may also be prepared from alkyl halides in amine alkylation , Gabriel synthesis and Delepine reaction , by undergoing nucleophilic substitution with potassium phthalimide or hexamine respectively, followed by hydrolysis. In

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3780-414: Is used. To reduce confusion this article follows the systematic naming scheme throughout. Haloalkanes can be produced from virtually all organic precursors. From the perspective of industry, the most important ones are alkanes and alkenes. Alkanes react with halogens by free radical halogenation . In this reaction a hydrogen atom is removed from the alkane, then replaced by a halogen atom by reaction with

3870-493: The International Union of Pure and Applied Chemistry (IUPAC) adopted the isotope carbon-12 as the basis for atomic weights . Identification of carbon in nuclear magnetic resonance (NMR) experiments is done with the isotope C. Carbon-14 ( C) is a naturally occurring radioisotope , created in the upper atmosphere (lower stratosphere and upper troposphere ) by interaction of nitrogen with cosmic rays. It

3960-642: The Lucas test . In the laboratory, more active deoxygenating and halogenating agents combine with base to effect the conversion. In the " Darzens halogenation ", thionyl chloride ( SOCl 2 ) with pyridine converts less reactive alcohols to chlorides. Both phosphorus pentachloride ( PCl 5 ) and phosphorus trichloride ( PCl 3 ) function similarly, and alcohols convert to bromoalkanes under hydrobromic acid or phosphorus tribromide (PBr 3 ). The heavier halogens do not require preformed reagents: A catalytic amount of PBr 3 may be used for

4050-553: The Mitsunobu reaction , the reagents are any nucleophile , triphenylphosphine, and a diazodicarboxylate ; the coproducts are triphenyl­phosphine oxide and a hydrazodiamide . Two methods for the synthesis of haloalkanes from carboxylic acids are Hunsdiecker reaction and Kochi reaction . Many chloro and bromoalkanes are formed naturally. The principal pathways involve the enzymes chloroperoxidase and bromoperoxidase . Primary aromatic amines yield diazonium ions in

4140-512: The PAH world hypothesis where they are hypothesized to have a role in abiogenesis and formation of life. PAHs seem to have been formed "a couple of billion years" after the Big Bang , are widespread throughout the universe, and are associated with new stars and exoplanets . It has been estimated that the solid earth as a whole contains 730 ppm of carbon, with 2000 ppm in the core and 120 ppm in

4230-425: The aurophilicity of the gold ligands, which provide additional stabilization of an otherwise labile species. In nature, the iron-molybdenum cofactor ( FeMoco ) responsible for microbial nitrogen fixation likewise has an octahedral carbon center (formally a carbide, C(-IV)) bonded to six iron atoms. In 2016, it was confirmed that, in line with earlier theoretical predictions, the hexamethylbenzene dication contains

4320-695: The biosphere has been estimated at 550 gigatonnes but with a large uncertainty, due mostly to a huge uncertainty in the amount of terrestrial deep subsurface bacteria . Hydrocarbons (such as coal, petroleum, and natural gas) contain carbon as well. Coal "reserves" (not "resources") amount to around 900 gigatonnes with perhaps 18,000 Gt of resources. Oil reserves are around 150 gigatonnes. Proven sources of natural gas are about 175 × 10  cubic metres (containing about 105 gigatonnes of carbon), but studies estimate another 900 × 10  cubic metres of "unconventional" deposits such as shale gas , representing about 540 gigatonnes of carbon. Carbon

4410-455: The carbon cycle . For example, photosynthetic plants draw carbon dioxide from the atmosphere (or seawater) and build it into biomass, as in the Calvin cycle , a process of carbon fixation . Some of this biomass is eaten by animals, while some carbon is exhaled by animals as carbon dioxide. The carbon cycle is considerably more complicated than this short loop; for example, some carbon dioxide

4500-399: The submillimeter wavelength range, and are used in the study of newly forming stars in molecular clouds . Under terrestrial conditions, conversion of one element to another is very rare. Therefore, the amount of carbon on Earth is effectively constant. Thus, processes that use carbon must obtain it from somewhere and dispose of it somewhere else. The paths of carbon in the environment form

4590-404: The R synthon , and readily react with nucleophiles. Hydrolysis , a reaction in which water breaks a bond, is a good example of the nucleophilic nature of haloalkanes. The polar bond attracts a hydroxide ion, OH (NaOH (aq) being a common source of this ion). This OH is a nucleophile with a clearly negative charge, as it has excess electrons it donates them to the carbon, which results in

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4680-857: The R synthon. Alkali metals such as sodium and lithium are able to cause haloalkanes to couple in Wurtz reaction , giving symmetrical alkanes. Haloalkanes, especially iodoalkanes, also undergo oxidative addition reactions to give organometallic compounds . Chlorinated or fluorinated alkenes undergo polymerization. Important halogenated polymers include polyvinyl chloride (PVC), and polytetrafluoroethene (PTFE, or teflon). Nature produces massive amounts of chloromethane and bromomethane. Most concern focuses on anthropogenic sources, which are potential toxins, even carcinogens. Similarly, great interest has been shown in remediation of man made halocarbons such as those produced on large scale, such as dry cleaning fluids. Volatile halocarbons degrade photochemically because

4770-645: The Russian Arctic, Brazil, and in Northern and Western Australia. Diamonds are now also being recovered from the ocean floor off the Cape of Good Hope . Diamonds are found naturally, but about 30% of all industrial diamonds used in the U.S. are now manufactured. Carbon-14 is formed in upper layers of the troposphere and the stratosphere at altitudes of 9–15 km by a reaction that is precipitated by cosmic rays . Thermal neutrons are produced that collide with

4860-459: The Solar System was still a protoplanetary disk . Microscopic diamonds may also be formed by the intense pressure and high temperature at the sites of meteorite impacts. In 2014 NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs) in the universe. More than 20% of the carbon in the universe may be associated with PAHs, complex compounds of carbon and hydrogen without oxygen. These compounds figure in

4950-503: The addition of phosphorus to these other elements, it forms DNA and RNA , the chemical-code carriers of life, and adenosine triphosphate (ATP), the most important energy-transfer molecule in all living cells. Norman Horowitz , head of the Mariner and Viking missions to Mars (1965–1976), considered that the unique characteristics of carbon made it unlikely that any other element could replace carbon, even on another planet, to generate

5040-510: The allotropic form. For example, graphite is opaque and black, while diamond is highly transparent . Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known. Graphite is a good electrical conductor while diamond has a low electrical conductivity . Under normal conditions, diamond, carbon nanotubes , and graphene have

5130-451: The biochemistry necessary for life. Commonly carbon-containing compounds which are associated with minerals or which do not contain bonds to the other carbon atoms, halogens, or hydrogen, are treated separately from classical organic compounds; the definition is not rigid, and the classification of some compounds can vary from author to author (see reference articles above). Among these are the simple oxides of carbon. The most prominent oxide

5220-529: The carbon is bonded to. In general, covalent radius decreases with lower coordination number and higher bond order. Carbon-based compounds form the basis of all known life on Earth, and the carbon-nitrogen-oxygen cycle provides a small portion of the energy produced by the Sun, and most of the energy in larger stars (e.g. Sirius ). Although it forms an extraordinary variety of compounds, most forms of carbon are comparatively unreactive under normal conditions. At standard temperature and pressure, it resists all but

5310-679: The carbon that carries the halogen atom has three C–C bonds. Haloalkanes can also be classified according to the type of halogen on group 17 responding to a specific halogenoalkane. Haloalkanes containing carbon bonded to fluorine , chlorine , bromine , and iodine results in organofluorine , organochlorine , organobromine and organoiodine compounds, respectively. Compounds containing more than one kind of halogen are also possible. Several classes of widely used haloalkanes are classified in this way chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). These abbreviations are particularly common in discussions of

5400-414: The carbon to which the halogen is attached is slightly electropositive where the halogen is slightly electronegative . This results in an electron deficient (electrophilic) carbon which, inevitably, attracts nucleophiles . Substitution reactions involve the replacement of the halogen with another molecule—thus leaving saturated hydrocarbons , as well as the halogenated product. Haloalkanes behave as

5490-435: The carbon-halogen bond can be labile. Some microorganisms dehalogenate halocarbons. While this behavior is intriguing, the rates of remediation are generally very slow. As alkylating agents , haloalkanes are potential carcinogens. The more reactive members of this large class of compounds generally pose greater risk, e.g. carbon tetrachloride . Carbon Carbon (from Latin carbo  'coal')

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5580-406: The coal-gas reaction used in coal gasification : Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide cementite in steel and tungsten carbide , widely used as an abrasive and for making hard tips for cutting tools. The system of carbon allotropes spans a range of extremes: Atomic carbon is a very short-lived species and, therefore, carbon

5670-489: The combined mantle and crust. Since the mass of the earth is 5.972 × 10  kg , this would imply 4360 million gigatonnes of carbon. This is much more than the amount of carbon in the oceans or atmosphere (below). In combination with oxygen in carbon dioxide, carbon is found in the Earth's atmosphere (approximately 900 gigatonnes of carbon — each ppm corresponds to 2.13 Gt) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Carbon in

5760-453: The conclusion that as T → 0 K and p → 0 Pa , diamond becomes more stable than graphite by approximately 1.1 kJ/mol, more recent and definitive experimental and computational studies show that graphite is more stable than diamond for T < 400 K , without applied pressure, by 2.7 kJ/mol at T  = 0 K and 3.2 kJ/mol at T  = 298.15 K. Under some conditions, carbon crystallizes as lonsdaleite ,

5850-451: The environmental impact of haloalkanes. Haloalkanes generally resemble the parent alkanes in being colorless, relatively odorless, and hydrophobic. The melting and boiling points of chloro-, bromo-, and iodoalkanes are higher than the analogous alkanes, scaling with the atomic weight and number of halides. This effect is due to the increased strength of the intermolecular forces —from London dispersion to dipole-dipole interaction because of

5940-503: The formal electron count of these species does not exceed an octet. This makes them hypercoordinate but not hypervalent. Even in cases of alleged 10-C-5 species (that is, a carbon with five ligands and a formal electron count of ten), as reported by Akiba and co-workers, electronic structure calculations conclude that the electron population around carbon is still less than eight, as is true for other compounds featuring four-electron three-center bonding . The English name carbon comes from

6030-484: The future, but is currently technologically impossible. Isotopes of carbon are atomic nuclei that contain six protons plus a number of neutrons (varying from 2 to 16). Carbon has two stable, naturally occurring isotopes. The isotope carbon-12 ( C) forms 98.93% of the carbon on Earth, while carbon-13 ( C) forms the remaining 1.07%. The concentration of C is further increased in biological materials because biochemical reactions discriminate against C. In 1961,

6120-461: The halogen as a prefix to the alkane. For example, ethane with bromine becomes bromoethane , methane with four chlorine groups becomes tetrachloromethane . However, many of these compounds have already an established trivial name, which is endorsed by the IUPAC nomenclature, for example chloroform (trichloromethane) and methylene chloride ( dichloromethane ). But nowadays, IUPAC nomenclature

6210-423: The heavier group-14 elements. The electronegativity of carbon is 2.5, significantly higher than the heavier group-14 elements (1.8–1.9), but close to most of the nearby nonmetals, as well as some of the second- and third-row transition metals . Carbon's covalent radii are normally taken as 77.2 pm (C−C), 66.7 pm (C=C) and 60.3 pm (C≡C), although these may vary depending on coordination number and what

6300-675: The highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure. They are chemically resistant and require high temperature to react even with oxygen. The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones , dolomites and carbon dioxide , but significant quantities occur in organic deposits of coal , peat , oil , and methane clathrates . Carbon forms

6390-509: The highest-melting-point metals such as tungsten or rhenium . Although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper, which are weaker reducing agents at room temperature. Carbon is the sixth element, with a ground-state electron configuration of 1s 2s 2p , of which the four outer electrons are valence electrons . Its first four ionisation energies, 1086.5, 2352.6, 4620.5 and 6222.7 kJ/mol, are much higher than those of

6480-463: The hydrogen atom of the hydrohalic acid. Markovnikov's rule states that under normal conditions, hydrogen is attached to the unsaturated carbon with the most hydrogen substituents. The rule is violated when neighboring functional groups polarize the multiple bond, or in certain additions of hydrogen bromide (addition in the presence of peroxides and the Wohl-Ziegler reaction ) which occur by

6570-651: The hydroxide ion HO abstracts a hydrogen atom. A Bromide ion is then lost, resulting in ethene , H 2 O and NaBr. Thus, haloalkanes can be converted to alkenes. Similarly, dihaloalkanes can be converted to alkynes . In related reactions, 1,2-dibromocompounds are debrominated by zinc dust to give alkenes and geminal dihalides can react with strong bases to give carbenes . Haloalkanes undergo free-radical reactions with elemental magnesium to give alkyl-magnesium compound: Grignard reagent . Haloalkanes also react with lithium metal to give organolithium compounds . Both Grignard reagents and organolithium compounds behave as

6660-443: The increased polarizability. Thus tetraiodomethane ( CI 4 ) is a solid whereas tetrachloromethane ( CCl 4 ) is a liquid. Many fluoroalkanes, however, go against this trend and have lower melting and boiling points than their nonfluorinated analogues due to the decreased polarizability of fluorine. For example, methane ( CH 4 ) has a melting point of −182.5 °C whereas tetrafluoromethane ( CF 4 ) has

6750-414: The manufacture of plastics and petrochemicals, and as fossil fuels. When combined with oxygen and hydrogen, carbon can form many groups of important biological compounds including sugars, lignans , chitins , alcohols, fats, aromatic esters , carotenoids and terpenes . With nitrogen, it forms alkaloids , and with the addition of sulfur also it forms antibiotics, amino acids , and rubber products. With

6840-538: The most active (fluoroalkanes do not act as alkylating agents under normal conditions). The ozone-depleting abilities of the CFCs arises from the photolability of the C–Cl bond. An estimated 4,100,000,000 kg of chloromethane are produced annually by natural sources. The oceans are estimated to release 1 to 2 million tons of bromomethane annually. The formal naming of haloalkanes should follow IUPAC nomenclature , which put

6930-1053: The most polar and salt-like of carbides are not completely ionic compounds. Organometallic compounds by definition contain at least one carbon-metal covalent bond. A wide range of such compounds exist; major classes include simple alkyl-metal compounds (for example, tetraethyllead ), η -alkene compounds (for example, Zeise's salt ), and η -allyl compounds (for example, allylpalladium chloride dimer ); metallocenes containing cyclopentadienyl ligands (for example, ferrocene ); and transition metal carbene complexes . Many metal carbonyls and metal cyanides exist (for example, tetracarbonylnickel and potassium ferricyanide ); some workers consider metal carbonyl and cyanide complexes without other carbon ligands to be purely inorganic, and not organometallic. However, most organometallic chemists consider metal complexes with any carbon ligand, even 'inorganic carbon' (e.g., carbonyls, cyanides, and certain types of carbides and acetylides) to be organometallic in nature. Metal complexes containing organic ligands without

7020-408: The nuclei of nitrogen-14, forming carbon-14 and a proton. As such, 1.5% × 10 of atmospheric carbon dioxide contains carbon-14. Carbon-rich asteroids are relatively preponderant in the outer parts of the asteroid belt in the Solar System. These asteroids have not yet been directly sampled by scientists. The asteroids can be used in hypothetical space-based carbon mining , which may be possible in

7110-423: The outer wall of a nanotube) that combine the properties of both in a single structure. Of the other discovered allotropes, carbon nanofoam is a ferromagnetic allotrope discovered in 1997. It consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web, in which the atoms are bonded trigonally in six- and seven-membered rings. It is among the lightest known solids, with

7200-451: The presence of a base, haloalkanes alkylate alcohols, amines, and thiols to obtain ethers , N -substituted amines, and thioethers respectively. They are substituted by Grignard reagent to give magnesium salts and an extended alkyl compound. In dehydrohalogenation reactions, the halogen and an adjacent proton are removed from halocarbons, thus forming an alkene . For example, with bromoethane and sodium hydroxide (NaOH) in ethanol ,

7290-526: The rapid expansion and cooling of the early universe prohibited, and therefore no significant carbon was created during the Big Bang. According to current physical cosmology theory, carbon is formed in the interiors of stars on the horizontal branch . When massive stars die as supernova, the carbon is scattered into space as dust. This dust becomes component material for the formation of the next-generation star systems with accreted planets. The Solar System

7380-490: The selective formation of C-halogen bonds. Especially versatile methods included the addition of halogens to alkenes, hydrohalogenation of alkenes, and the conversion of alcohols to alkyl halides. These methods are so reliable and so easily implemented that haloalkanes became cheaply available for use in industrial chemistry because the halide could be further replaced by other functional groups. While many haloalkanes are human-produced, substantial amounts are biogenic. From

7470-470: The strongest oxidizers. It does not react with sulfuric acid , hydrochloric acid , chlorine or any alkalis . At elevated temperatures, carbon reacts with oxygen to form carbon oxides and will rob oxygen from metal oxides to leave the elemental metal. This exothermic reaction is used in the iron and steel industry to smelt iron and to control the carbon content of steel : Carbon reacts with sulfur to form carbon disulfide , and it reacts with steam in

7560-435: The structural perspective, haloalkanes can be classified according to the connectivity of the carbon atom to which the halogen is attached. In primary (1°) haloalkanes, the carbon that carries the halogen atom is only attached to one other alkyl group. An example is chloroethane ( CH 3 CH 2 Cl ). In secondary (2°) haloalkanes, the carbon that carries the halogen atom has two C–C bonds. In tertiary (3°) haloalkanes,

7650-509: The structure of fullerenes. The buckyballs are fairly large molecules formed completely of carbon bonded trigonally, forming spheroids (the best-known and simplest is the soccerball-shaped C 60 buckminsterfullerene ). Carbon nanotubes (buckytubes) are structurally similar to buckyballs, except that each atom is bonded trigonally in a curved sheet that forms a hollow cylinder . Nanobuds were first reported in 2007 and are hybrid buckytube/buckyball materials (buckyballs are covalently bonded to

7740-414: The systematic study and categorization of organic compounds. Chain length, shape and functional groups all affect the properties of organic molecules. In most stable compounds of carbon (and nearly all stable organic compounds), carbon obeys the octet rule and is tetravalent , meaning that a carbon atom forms a total of four covalent bonds (which may include double and triple bonds). Exceptions include

7830-460: The temperatures commonly encountered on Earth, enables this element to serve as a common element of all known life . It is the second most abundant element in the human body by mass (about 18.5%) after oxygen. The atoms of carbon can bond together in diverse ways, resulting in various allotropes of carbon . Well-known allotropes include graphite , diamond , amorphous carbon , and fullerenes . The physical properties of carbon vary widely with

7920-458: The total going to the atmosphere, sea, and land (such as peat bogs ) at almost 2,000 Gt. Carbon is a constituent (about 12% by mass) of the very large masses of carbonate rock ( limestone , dolomite , marble , and others). Coal is very rich in carbon ( anthracite contains 92–98%) and is the largest commercial source of mineral carbon, accounting for 4,000 gigatonnes or 80% of fossil fuel . As for individual carbon allotropes, graphite

8010-499: The transformation using phosphorus and bromine; PBr 3 is formed in situ . Iodoalkanes may similarly be prepared using red phosphorus and iodine (equivalent to phosphorus triiodide ). One family of named reactions relies on the deoxygenating effect of triphenylphosphine . In the Appel reaction , the reagent is tetrahalomethane and triphenylphosphine ; the co-products are haloform and triphenylphosphine oxide . In

8100-775: The unstable dicarbon monoxide (C 2 O), carbon trioxide (CO 3 ), cyclopentanepentone (C 5 O 5 ), cyclohexanehexone (C 6 O 6 ), and mellitic anhydride (C 12 O 9 ). However, mellitic anhydride is the triple acyl anhydride of mellitic acid; moreover, it contains a benzene ring. Thus, many chemists consider it to be organic. With reactive metals, such as tungsten , carbon forms either carbides (C ) or acetylides ( C 2 ) to form alloys with high melting points. These anions are also associated with methane and acetylene , both very weak acids. With an electronegativity of 2.5, carbon prefers to form covalent bonds . A few carbides are covalent lattices, like carborundum (SiC), which resembles diamond. Nevertheless, even

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