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Bromofluoromethane
Bromofluoromethane is a mixed gaseous halomethane soluble in alcohol and very soluble in chloroform. Its standard molar entropy, ''S''ogas is 276.3 J/(mol K) and heat capacity, ''cp'' is 49.2 J/(mol K). Preparation Up to date, it has been prepared by three prevailingly ineffective methods: # From salts of fluoroacetic acid using a Hunsdiecker type of reaction. # From dibromofluoromethane by reductive debromination with a Swarts reagent. # From a dihalomethane by an halogen exchange reaction or from a halomethane by catalyzed bromination or fluorination. The method with the highest yield is reductive debromination of dibromofluoromethane using an organotin hydride. Uses Bromofluoromethane is an important reagent in the manufacture of intermediates, pharmaceuticals and other chemicals. Usage of bromofluoromethane is regulated due to its ozone depletion potential The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dibromofluoromethane
Dibromofluoromethane is a mixed halomethane. It is soluble in alcohol, acetone, benzene and chloroform. Applications It can be used to prepare bromofluoromethane by reductive debromination with organotin hydride as tributyltin hydride. Regulations Its ozone depletion potential The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane (R-11 or CFC-11) being fixed at an ODP of 1.0. Chlorodifluoromethane (R-22), for exampl ... (ODP) is 1.0 and it is included in list of Class I Ozone-Depleting Substances. References Halomethanes Ozone depletion Organobromides Organofluorides {{organohalide-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halomethane
Halomethane compounds are derivatives of methane () with one or more of the hydrogen atoms replaced with halogen atoms ( F, Cl, Br, or I). Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably as refrigerants, solvents, propellants, and fumigants. Many, including the chlorofluorocarbons, have attracted wide attention because they become active when exposed to ultraviolet light found at high altitudes and destroy the Earth's protective ozone layer. Structure and properties Like methane itself, halomethanes are tetrahedral molecules. The halogen atoms differ greatly in size and charge from hydrogen and from each other. Consequently, most halomethanes deviate from the perfect tetrahedral symmetry of methane.Günter Siegemund, Werner Schwertfeger, Andrew Feiring, Bruce Smart, Fred Behr, Herward Vogel, Blaine McKusick “Fluorine Compounds, Organic” Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. The ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a hydroxyl group). Ethanol is a volatile, flammable, colorless liquid with a characteristic wine-like odor and pungent taste. It is a psychoactive recreational drug, the active ingredient in alcoholic drinks. Ethanol is naturally produced by the fermentation process of sugars by yeasts or via petrochemical processes such as ethylene hydration. It has medical applications as an antiseptic and disinfectant. It is used as a chemical solvent and in the synthesis of organic compounds, and as a fuel source. Ethanol also can be dehydrated to make ethylene, an important chemical feedstock. As of 2006, world production of ethanol was , coming mostly from Brazil and the U.S. Etymology ''Ethanol'' is the systematic name defined by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chloroform
Chloroform, or trichloromethane, is an organic compound with formula C H Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to PTFE. It is also a precursor to various refrigerants. It is trihalomethane. It is a powerful anesthetic, euphoriant, anxiolytic, and sedative when inhaled or ingested. Structure The molecule adopts a tetrahedral molecular geometry with C3v symmetry. Natural occurrence The total global flux of chloroform through the environment is approximately tonnes per year, and about 90% of emissions are natural in origin. Many kinds of seaweed produce chloroform, and fungi are believed to produce chloroform in soil. Abiotic processes are also believed to contribute to natural chloroform productions in soils although the mechanism is still unclear. Chloroform volatilizes readily from soil and surface water and undergoes degradation in air to produce phosgene, dichloromethane, formyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Molar Entropy
In chemistry, the standard molar entropy is the entropy content of one mole of pure substance at a standard state of pressure and any temperature of interest. These are often (but not necessarily) chosen to be the standard temperature and pressure. The standard molar entropy at pressure = P^0 is usually given the symbol , and has units of joules per mole per kelvin (J⋅mol−1⋅K−1). Unlike standard enthalpies of formation, the value of is absolute. That is, an element in its standard state has a definite, nonzero value of at room temperature. The entropy of a pure crystalline structure can be 0J⋅mol−1⋅K−1 only at 0K, according to the third law of thermodynamics. However, this assumes that the material forms a ' perfect crystal' without any residual entropy. This can be due to crystallographic defects, dislocations, and/or incomplete rotational quenching within the solid, as originally pointed out by Linus Pauling. These contributions to the entropy are always p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Capacity
Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K). Heat capacity is an extensive property. The corresponding intensive property is the specific heat capacity, found by dividing the heat capacity of an object by its mass. Dividing the heat capacity by the amount of substance in moles yields its molar heat capacity. The volumetric heat capacity measures the heat capacity per volume. In architecture and civil engineering, the heat capacity of a building is often referred to as its thermal mass. Definition Basic definition The heat capacity of an object, denoted by C, is the limit : C = \lim_\frac, where \Delta Q is the amount of heat that must be added to the object (of mass ''M'') in order to raise its temperature by \Delta T. The value of this parameter usually varies considerably depending on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluoroacetic Acid
Fluoroacetic acid is a organofluorine compound with formula CH2FCO2H. It is a colorless solid that is noted for its relatively high toxicity. The conjugate base, fluoroacetate occurs naturally in at least 40 plants in Australia, Brazil, and Africa. It is one of only five known organic fluorine-containing natural products. Toxicity Fluoroacetic acid is a harmful metabolite of some fluorine-containing drugs (median lethal dose, LD50 = 10 mg/kg in humans). The most common metabolic sources of fluoroacetic acid are fluoroamines and fluoroethers. Fluoroacetic acid can disrupt the Krebs cycle. In contrast with monofluoroacetic acid, difluoroacetic acid and trifluoroacetic acid are far less toxic. Its pKa is 2.66, in contrast to 1.24 and 0.23 for the respective di- and trifluorinated acids. Uses Fluoroacetic acid is used to manufacture pesticides especially rodenticides Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halogenation
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens (F2, Cl2, Br2, I2). Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride. Organic chemistry Several pathways exist for the halogenation of organic compounds, including free radical halogenation, ketone halogenation, electrophilic halogenation, and halogen addition reaction. The nature of the substrate determines the pathway. The facility of halogenation is influenced by the halogen. Fluorine and chlorine are more electrophilic and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ozone Depletion Potential
The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane (R-11 or CFC-11) being fixed at an ODP of 1.0. Chlorodifluoromethane (R-22), for example, has an ODP of 0.05. CFC 11, or R-11 has the maximum potential amongst chlorocarbons because of the presence of three chlorine atoms in the molecule. The first proposal of ODP came from Wuebbles in 1983. It was defined as a measure of destructive effects of a substance compared to a reference substance. Precisely, ODP of a given substance is defined as the ratio of global loss of ozone due to the given substance to the global loss of ozone due to CFC-11 of the same mass. ODP can be estimated from the molecular structure of a given substance. Chlorofluorocarbons have ODPs roughly equal to 1. Brominated substances have usually higher ODPs in range 5–15, because of the more aggressive bromine reaction with ozone. Hydrochlorofluorocarbon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorine-18
Fluorine-18 (18F) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96% of the time and electron capture 4% of the time. Both modes of decay yield stable oxygen-18. Natural occurrence is a natural trace radioisotope produced by cosmic ray spallation of atmospheric argon as well as by reaction of protons with natural oxygen: 18O + p → 18F + n.18O">sup>18Oater with high energy protons (typically ~18 MeV). The fluorine produced is in the form of a water solution of 18F.html" ;"title="sup>18F">sup>18F luoride, which is then used in a rapid chemical synthesis of various radio pharmaceuticals. The organic oxygen-18 pharmaceutical molecule is not made before the production of the radiopharmaceutical, as high energy protons destroy such molecules (radiolysis). Radiopharmaceuticals using fluorine must therefore be synthesized after the fluorine-18 has been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corvallis, Oregon
Corvallis ( ) is a city and the county seat of Benton County in central western Oregon, United States. It is the principal city of the Corvallis, Oregon Metropolitan Statistical Area, which encompasses all of Benton County. As of the 2020 United States Census, the population was 59,922. Corvallis is the location of Oregon State University and Good Samaritan Regional Medical Center. Corvallis is the westernmost city in the contiguous 48 states with a population larger than 50,000. History Establishment In October 1845, Joseph C. Avery arrived in Oregon from the east.David D. Fagan''History of Benton County, Oregon: Including... a Full Political History, ...Incidents of Pioneer Life, and Biographical Sketches of Early and Prominent Citizens...''Portland, OR: A.G. Walling, Printer, 1885; pg. 422. Note that a clear typographical error in the original source has Avery's date of arrival as "October 1846", but beginning of his residence in "June 1846." Avery took out a land claim a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halomethanes
Halomethane compounds are derivatives of methane () with one or more of the hydrogen atoms replaced with halogen atoms ( F, Cl, Br, or I). Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably as refrigerants, solvents, propellants, and fumigants. Many, including the chlorofluorocarbons, have attracted wide attention because they become active when exposed to ultraviolet light found at high altitudes and destroy the Earth's protective ozone layer. Structure and properties Like methane itself, halomethanes are tetrahedral molecules. The halogen atoms differ greatly in size and charge from hydrogen and from each other. Consequently, most halomethanes deviate from the perfect tetrahedral symmetry of methane.Günter Siegemund, Werner Schwertfeger, Andrew Feiring, Bruce Smart, Fred Behr, Herward Vogel, Blaine McKusick “Fluorine Compounds, Organic” Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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