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44-404: It required 22,000 tons of steel; its heaviest component is 40.2 tons. The structure is hot-dip galvanized and treated with fluorocarbon paint. It uses 850,000 high-strength bolt connections, replacing high-altitude welding technology. The installation accuracy is 99.98% . The outer surface is a hyperbolic parabola . From the air, it looks like a plum blossom with five petals. The plum blossom

88-465: A bent bond. Of these two models, hyperconjugation is generally considered the principal cause behind the gauche effect in difluoroethane. The carbon–fluorine bond stretching appears in the infrared spectrum between 1000 and 1360 cm . The wide range is due to the sensitivity of the stretching frequency to other substituents in the molecule. Monofluorinated compounds have a strong band between 1000 and 1110 cm ; with more than one fluorine atoms,

132-445: A building area of 1,142 square meters and an operating area of 940 square meters, serving the main business projects for high-altitude adventure projects. In February 2005, the project was approved by the national development and reform commission, PRC . In April 2006, the preliminary design began. In November 2006, the design was offered by the architectural design and research institute of Tongji university. On December 27, 2006,

176-501: A very low solubility in them (on the order of 10 ppm). They have low refractive indices . As the high electronegativity of fluorine reduces the polarizability of the atom, fluorocarbons are only weakly susceptible to the fleeting dipoles that form the basis of the London dispersion force . As a result, fluorocarbons have low intermolecular attractive forces and are lipophobic in addition to being hydrophobic and non-polar . Reflecting

220-506: A very wide range, depending on the degree of substitution and functional group. The table below shows the ranges for some of the major classes. Breaking C–F bonds is of interest as a way to decompose and destroy organofluorine " forever chemicals " such as PFOA and perfluorinated compounds (PFCs). Candidate methods include catalysts, such as platinum atoms; photocatalysts; UV, iodide, and sulfite, radicals; etc. Some metal complexes cleave C-F bonds. These reactions are of interest from

264-403: Is tetrafluoroethylene , which is used to manufacture polytetrafluoroethylene (PTFE), better known under the trade name Teflon . Fluoroalkenes and fluorinated alkynes are reactive and many are toxic for example perfluoroisobutene . To produce polytetrafluoroethylene various fluorinated surfactants are used, in the process known as Emulsion polymerization , and the surfactant included in

308-427: Is also observed for 1,2-dimethoxyethane . A related effect is the alkene cis effect . For instance, the cis isomer of 1,2-difluoroethylene is more stable than the trans isomer. There are two main explanations for the gauche effect: hyperconjugation and bent bonds . In the hyperconjugation model, the donation of electron density from the carbon–hydrogen σ bonding orbital to the carbon–fluorine σ antibonding orbital

352-473: Is attributed to the weak intermolecular interactions in these fluorocarbon fluids. The table shows values for the mole fraction, x 1 , of nitrogen dissolved, calculated from the Blood–gas partition coefficient , at 298.15 K (25 °C), 0.101325 MPa. The development of the fluorocarbon industry coincided with World War II . Prior to that, fluorocarbons were prepared by reaction of fluorine with

396-419: Is considered the source of stabilization in the gauche isomer. Due to the greater electronegativity of fluorine, the carbon–hydrogen σ orbital is a better electron donor than the carbon–fluorine σ orbital, while the carbon–fluorine σ orbital is a better electron acceptor than the carbon–hydrogen σ orbital. Only the gauche conformation allows good overlap between the better donor and the better acceptor. Key in

440-531: Is covered by the Kyoto Protocol . The global warming potential (compared to that of carbon dioxide) of many gases can be found in the IPCC 5th assessment report, with an extract below for a few perfluoroalkanes. The aluminium smelting industry has been a major source of atmospheric perfluorocarbons ( tetrafluoromethane and hexafluoroethane especially), produced as by-product of the electrolysis process. However,

484-627: Is labeled as "the strongest in organic chemistry," because fluorine forms the strongest single bond to carbon. Carbon–fluorine bonds can have a bond dissociation energy (BDE) of up to 130 kcal/mol. The BDE (strength of the bond) of C–F is higher than other carbon– halogen and carbon– hydrogen bonds. For example, the BDEs of the C–X bond within a CH 3 –X molecule is 115, 104.9, 83.7, 72.1, and 57.6 kcal/mol for X = fluorine, hydrogen , chlorine , bromine , and iodine , respectively. The carbon–fluorine bond length

SECTION 10

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528-415: Is more stable than the anti conformer—this is the opposite of what would normally be expected and to what is observed for most 1,2-disubstituted ethanes; this phenomenon is known as the gauche effect . In 1,2-difluoroethane, the gauche conformation is more stable than the anti conformation by 2.4 to 3.4 kJ/mole in the gas phase. This effect is not unique to the halogen fluorine, however; the gauche effect

572-552: Is one of the strongest single bonds in chemistry (after the B–F single bond, Si–F single bond, and H–F single bond), and relatively short, due to its partial ionic character. The bond also strengthens and shortens as more fluorines are added to the same carbon on a chemical compound . As such, fluoroalkanes like tetrafluoromethane (carbon tetrafluoride) are some of the most unreactive organic compounds. The high electronegativity of fluorine (4.0 for fluorine vs. 2.5 for carbon) gives

616-462: Is recovered from the top. Electrochemical fluorination (ECF) (also known as the Simons' process) involves electrolysis of a substrate dissolved in hydrogen fluoride . As fluorine is itself manufactured by the electrolysis of hydrogen fluoride, ECF is a rather more direct route to fluorocarbons. The process proceeds at low voltage (5 – 6 V) so that free fluorine is not liberated. The choice of substrate

660-470: Is restricted as ideally it should be soluble in hydrogen fluoride. Ethers and tertiary amines are typically employed. To make perfluorohexane, trihexylamine is used, for example: The perfluorinated amine will also be produced: Fluoroalkanes are generally inert and non-toxic. Fluoroalkanes are not ozone depleting , as they contain no chlorine or bromine atoms, and they are sometimes used as replacements for ozone-depleting chemicals. The term fluorocarbon

704-471: Is the provincial flower of Henan province . Five petals are homophonic with " five blessings " in Chinese. Looking up from the ground, the tower is like a static firework that spins upward and flies gracefully. The shape of the tower base is like a tripod , which was a symbol of power and prestige in ancient China. The shape of the tower is like the ancient Chinese musical instrument Chime Bells , which symbolizes

748-457: Is the synthesis of perfluorohexane : The resulting cobalt difluoride is then regenerated, sometimes in a separate reactor: Industrially, both steps are combined, for example in the manufacture of the Flutec range of fluorocarbons by F2 chemicals Ltd, using a vertical stirred bed reactor, with hydrocarbon introduced at the bottom, and fluorine introduced halfway up the reactor. The fluorocarbon vapor

792-400: Is too long to be representative of the lengths of the bonds between fluorine and other elements, so values between 54 pm and 60 pm have been suggested by other authors. With increasing number of fluorine atoms on the same ( geminal ) carbon the other bonds become stronger and shorter. This can be seen by the changes in bond length and strength (BDE) for the fluoromethane series, as shown on

836-433: Is typical for related alkynes, see dichloroacetylene ), hexafluoro-2-butyne and related fluorinated alkynes are well known. Fluoroalkenes polymerize more exothermically than normal alkenes. Unsaturated fluorocarbons have a driving force towards sp hybridization due to the electronegative fluorine atoms seeking a greater share of bonding electrons with reduced s character in orbitals. The most famous member of this class

880-451: Is typically about 1.35 ångström (1.39 Å in fluoromethane ). It is shorter than any other carbon–halogen bond, and shorter than single carbon– nitrogen and carbon– oxygen bonds. The short length of the bond can also be attributed to the ionic character of the bond (the electrostatic attractions between the partial charges on the carbon and the fluorine). The carbon–fluorine bond length varies by several hundredths of an ångstrom depending on

924-550: Is used rather loosely to include any chemical containing fluorine and carbon, including chlorofluorocarbons , which are ozone depleting. Perfluoroalkanes used in medical procedures are rapidly excreted from the body, primarily via expiration with the rate of excretion as a function of the vapour pressure; the half-life for octafluoropropane is less than 2 minutes, compared to about a week for perfluorodecalin. Low-boiling perfluoroalkanes are potent greenhouse gases , in part due to their very long atmospheric lifetime, and their use

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968-426: The band splits into two bands, one for the symmetric mode and one for the asymmetric. The carbon–fluorine bands are so strong that they may obscure any carbon–hydrogen bands that might be present. Organofluorine compounds can also be characterized using NMR spectroscopy , using carbon-13 , fluorine-19 (the only natural fluorine isotope), or hydrogen-1 (if present). The chemical shifts in F NMR appear over

1012-410: The bent bond explanation of the gauche effect in difluoroethane is the increased p orbital character of both carbon–fluorine bonds due to the large electronegativity of fluorine. As a result, electron density builds up above and below to the left and right of the central carbon–carbon bond. The resulting reduced orbital overlap can be partially compensated when a gauche conformation is assumed, forming

1056-400: The carbon–fluorine bond a significant polarity or dipole moment . The electron density is concentrated around the fluorine, leaving the carbon relatively electron poor. This introduces ionic character to the bond through partial charges (C —F ). The partial charges on the fluorine and carbon are attractive, contributing to the unusual bond strength of the carbon–fluorine bond. The bond

1100-565: The construction began formally. In March 2007, construction began. In October 2009, the tower was completed. The tower received the Zhan Tianyou civil engineering prize from China Civil Engineering Society in March, 2012. The panorama painting "Jinxiu Zhongyuan" (锦绣中原) in the third and fourth floor center was selected by the Guinness World Records as the largest panoramic painting in

1144-417: The corresponding aromatic compound, as the table below shows. They have high density and are non-flammable. For the most part, they are colorless liquids. Unlike the perfluoralkanes, they tend to be miscible with common solvents. Carbon%E2%80%93fluorine bond The carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds . It

1188-491: The corresponding perchloroaromatic compound with potassium fluoride at high temperature (typically 500 °C), during which the chlorine atoms are replaced by fluorine atoms. A third route is defluorination of the fluoroalkane; for example, octafluorotoluene can be made from perfluoromethylcyclohexane by heating to 500 °C with a nickel or iron catalyst. Perfluoroaromatic compounds are relatively volatile for their molecular weight, with melting and boiling points similar to

1232-495: The formula C x F y , meaning they contain only carbon and fluorine . The terminology is not strictly followed and many fluorine-containing organic compounds are also called fluorocarbons. Compounds with the prefix perfluoro- are hydrocarbons, including those with heteroatoms, wherein all C-H bonds have been replaced by C-F bonds. Fluorocarbons includes perfluoroalkanes, fluoroalkenes, fluoroalkynes, and perfluoroaromatic compounds. Perfluoroalkanes are very stable because of

1276-452: The hybridization of the carbon atom and the presence of other substituents on the carbon or even in atoms farther away. These fluctuations can be used as indication of subtle hybridization changes and stereoelectronic interactions . The table below shows how the average bond length varies in different bonding environments (carbon atoms are sp -hybridized unless otherwise indicated for sp or aromatic carbon). The variability in bond lengths and

1320-466: The hydrocarbon, i.e., direct fluorination. Because C-C bonds are readily cleaved by fluorine, direct fluorination mainly affords smaller perfluorocarbons, such as tetrafluoromethane, hexafluoroethane, and octafluoropropane. A major breakthrough that allowed the large scale manufacture of fluorocarbons was the Fowler process . In this process, cobalt trifluoride is used as the source of fluorine. Illustrative

1364-401: The industry has been actively involved in reducing emissions in recent years. As they are inert, perfluoroalkanes have essentially no chemical uses, but their physical properties have led to their use in many diverse applications. These include: As well as several medical uses: Unsaturated fluorocarbons are far more reactive than fluoroalkanes. Although difluoroacetylene is unstable (as

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1408-470: The moon: Relief 10: Jingwei fills up the sea; Relief 11: Xuan bird creates Shang dynasty ; Relief 12: Suiren products fire; Relief 13: Pangu creates the world. The first floor of the base houses the Henan cross-border trade exhibition and trading center. The second floor is 6.9 meters high, with VIP hall, press conference hall, tourist service center and other supporting facilities. Third and fourth floors of

1452-452: The most notable exception is perfluorocyclohexane , which sublimes at 51 °C. Fluorocarbons also have low surface energies and high dielectric strengths. In the 1960s there was a lot of interest in fluorocarbons as anesthetics. The research did not produce any anesthetics, but the research included tests on the issue of flammability, and showed that the tested fluorocarbons were not flammable in air in any proportion, though most of

1496-473: The perspectives of organic synthesis and remediation of xenochemicals. C-F bond activation has been classified as follows "(i) oxidative addition of fluorocarbon, (ii) M–C bond formation with HF elimination, (iii) M–C bond formation with fluorosilane elimination, (iv) hydrodefluorination of fluorocarbon with M–F bond formation, (v) nucleophilic attack on fluorocarbon, and (vi) defluorination of fluorocarbon". An illustrative metal-mediated C-F activation reaction

1540-504: The polymer can bioaccumulate. Perfluoroaromatic compounds contain only carbon and fluorine, like other fluorocarbons, but also contain an aromatic ring. The three most important examples are hexafluorobenzene , octafluorotoluene , and octafluoronaphthalene. Perfluoroaromatic compounds can be manufactured via the Fowler process, like fluoroalkanes, but the conditions must be adjusted to prevent full fluorination. They can also be made by heating

1584-420: The shortening of bonds to fluorine due to their partial ionic character are also observed for bonds between fluorine and other elements, and have been a source of difficulties with the selection of an appropriate value for the covalent radius of fluorine . Linus Pauling originally suggested 64 pm , but that value was eventually replaced by 72 pm, which is half of the fluorine–fluorine bond length. However, 72 pm

1628-884: The strength and stability of other nearby carbon–fluorine bonds on the same geminal carbon, as the carbon has a higher positive partial charge. Furthermore, multiple carbon–fluorine bonds also strengthen the "skeletal" carbon–carbon bonds from the inductive effect . Therefore, saturated fluorocarbons are more chemically and thermally stable than their corresponding hydrocarbon counterparts, and indeed any other organic compound. They are susceptible to attack by very strong reductants, e.g. Birch reduction and very specialized organometallic complexes. Fluorocarbons are colorless and have high density, up to over twice that of water. They are not miscible with most organic solvents (e.g., ethanol, acetone, ethyl acetate, and chloroform), but are miscible with some hydrocarbons (e.g., hexane in some cases). They have very low solubility in water, and water has

1672-414: The strength of the carbon–fluorine bond , one of the strongest in organic chemistry. Its strength is a result of the electronegativity of fluorine imparting partial ionic character through partial charges on the carbon and fluorine atoms, which shorten and strengthen the bond (compared to carbon-hydrogen bonds) through favorable covalent interactions. Additionally, multiple carbon–fluorine bonds increase

1716-420: The table below; also, the partial charges ( q C and q F ) on the atoms change within the series. The partial charge on carbon becomes more positive as fluorines are added, increasing the electrostatic interactions, and ionic character, between the fluorines and carbon. When two fluorine atoms are in vicinal (i.e., adjacent) carbons, as in 1,2-difluoroethane (H 2 FCCFH 2 ), the gauche conformer

1760-666: The tests were in pure oxygen or pure nitrous oxide (gases of importance in anesthesiology). In 1993, 3M considered fluorocarbons as fire extinguishants to replace CFCs. This extinguishing effect has been attributed to their high heat capacity , which takes heat away from the fire. It has been suggested that an atmosphere containing a significant percentage of perfluorocarbons on a space station or similar would prevent fires altogether. When combustion does occur, toxic fumes result, including carbonyl fluoride , carbon monoxide , and hydrogen fluoride . Perfluorocarbons dissolve relatively high volumes of gases. The high solubility of gases

1804-416: The tower host the largest panoramic painting in the world, "Jinxiu Zhongyuan" (锦绣中原). Ninety-seventh floor of tower has sightseeing service facilities. The 98th floor is 255 meters above the ground, with a construction area of 975 square metres (10,490 sq ft) and an operating area of 780 square meters. The revolving restaurant is located there. The 101st floor is 265 meters above the ground level, with

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1848-481: The tower's communication function. Zhongyuan tower is divided into four parts: tower base, tower body, tower and mast. The outer wall is decorated with reliefs: Relief 1: Nüwa creates mankind; Relief 2: Hou Yi shot down the sun. Relief 3: Shennong tastes herbs; Relief 4: Fuxi painting Bagua ; Relief 5: the store of Luoshen ; Relief 6: The Foolish old man removes the mountains ; Relief 7: Luoshu , Relief 8: Cangjie creates words, Relief 9: Chang'e flies to

1892-654: The weak intermolecular forces these compounds exhibit low viscosities when compared to liquids of similar boiling points , low surface tension and low heats of vaporization . The low attractive forces in fluorocarbon liquids make them compressible (low bulk modulus ) and able to dissolve gas relatively well. Smaller fluorocarbons are extremely volatile . There are five perfluoroalkane gases: tetrafluoromethane (bp −128 °C), hexafluoroethane (bp −78.2 °C), octafluoropropane (bp −36.5 °C), perfluoro-n-butane (bp −2.2 °C) and perfluoro-iso-butane (bp −1 °C). Nearly all other fluoroalkanes are liquids;

1936-442: The world on April 26, 2011. Fluorocarbon Fluorocarbons are chemical compounds with carbon-fluorine bonds . Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are commercial polymers , refrigerants , drugs , and anesthetics . Perfluorocarbons or PFCs , are organofluorine compounds with

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