|
Pyrene
Pyrene is a polycyclic aromatic hydrocarbon (PAH) consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is . This yellow-green solid is the smallest peri-fused PAH (one where the rings are fused through more than one face). Pyrene forms during incomplete combustion of organic compounds. Occurrence and properties Pyrene was first isolated from coal tar, where it occurs up to 2% by weight. As a peri-fused PAH, pyrene is much more resonance-stabilized than its five-member-ring containing isomer fluoranthene. Therefore, it is produced in a wide range of combustion conditions. For example, automobiles produce about 1 μg/km.Senkan, Selim and Castaldi, Marco (2003) "Combustion" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. Reactions Oxidation with chromate affords perinaphthenone and then naphthalene-1,4,5,8-tetracarboxylic acid. Pyrene undergoes a series of hydrogenation reactions and is susceptible to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzopyrene
A benzopyrene is an organic compound with the formula C20H12. Structurally speaking, the colorless isomers of benzopyrene are pentacyclic hydrocarbons and are fusion products of pyrene and a phenylene group. Two isomeric species of benzopyrene are benzo 'a''yrene and the less common benzo 'e''yrene. They belong to the chemical class of polycyclic aromatic hydrocarbons. Overview Related compounds include cyclopentapyrenes, dibenzopyrenes, indenopyrenes and naphthopyrenes. Benzopyrene is a component of pitch and occurs together with other related pentacyclic aromatic species such as picene, benzo fluoranthenes, and perylene. It is naturally emitted by forest fires and volcanic eruptions and can also be found in coal tar, cigarette smoke, wood smoke, and burnt foods such as coffee. Fumes that develop from fat dripping on blistering charcoal are rich in benzopyrene, which can condense on grilled goods. Benzopyrenes are harmful because they form carcinogenic and mutageni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycyclic Aromatic Hydrocarbon
A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, incinerators, in roasted meats and cereals, or when biomass burns at lower temperatures as in forest fires. The simplest representative is naphthalene, having two aromatic rings, and the three-ring compounds anthracene and phenanthrene. PAHs are uncharged, non-polar and planar. Many are colorless. Many of them are also found in fossil fuel deposits such as coal and in petroleum. Exposure to PAHs can lead to different types of cancer, to fetal development complications, and to cardiovascular issues. Polycyclic aromatic hydrocarbons are discussed as possible starting materials for abiotic syntheses of materials required by the earliest forms of life. Nomenclature and structure The terms polyaromatic hydrocarbon, or polynuclear aromatic hydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrenes
Pyrene is a polycyclic aromatic hydrocarbon (PAH) consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is . This yellow-green solid is the smallest peri-fused PAH (one where the rings are fused through more than one face). Pyrene forms during incomplete combustion of organic compounds. Occurrence and properties Pyrene was first isolated from coal tar, where it occurs up to 2% by weight. As a peri-fused PAH, pyrene is much more resonance-stabilized than its five-member-ring containing isomer fluoranthene. Therefore, it is produced in a wide range of combustion conditions. For example, automobiles produce about 1 μg/km.Senkan, Selim and Castaldi, Marco (2003) "Combustion" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. Reactions Oxidation with chromate affords perinaphthenone and then naphthalene-1,4,5,8-tetracarboxylic acid. Pyrene undergoes a series of hydrogenation reactions and is susceptible to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Interstellar And Circumstellar Molecules
This is a list of molecules that have been detected in the interstellar medium and circumstellar envelopes, grouped by the number of component atoms. The chemical formula is listed for each detected compound, along with any ionized form that has also been observed. Background The molecules listed below were detected through astronomical spectroscopy. Their spectral features arise because molecules either absorb or emit a photon of light when they transition between two molecular energy levels. The energy (and thus the wavelength) of the photon matches the energy difference between the levels involved. Molecular electronic transitions occur when one of the molecule's electrons moves between molecular orbitals, producing a spectral line in the ultraviolet, visible light, optical or near-infrared parts of the electromagnetic spectrum. Alternatively, a vibrational transition transfers Quantum, quanta of energy to (or from) vibrations of molecular bonds, producing signatures in the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perhydropyrene
Perhydropyrene is a hydrocarbon similar to pyrene. Single bonds with hydrogen replace the double bonds in the benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ... rings. External links * * Pyrenes Polycyclic nonaromatic hydrocarbons {{hydrocarbon-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coal Tar
Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It is a type of creosote. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoriasis and seborrheic dermatitis ( dandruff). It may be used in combination with ultraviolet light therapy. Industrially it is a railroad tie preservative and used in the surfacing of roads. Coal tar was listed as a known human carcinogen in the first Report on Carcinogens from the U.S. Federal Government, issued in 1980. Coal tar was discovered circa 1665 and used for medical purposes as early as the 1800s. Circa 1850, the discovery that it could be used as the main raw material for the synthesis of dyes engendered an entire industry. It is on the World Health Organization's List of Essential Medicines. Coal tar is available as a generic medication and over the counter. Side effects include skin irritation, sun sensitivity, aller ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyranine
Pyranine is a hydrophilic, pH-sensitive fluorescent dye from the group of chemicals known as arylsulfonates. Pyranine is soluble in water and is used as a coloring agent, biological stain, optical detecting reagent, and pH indicator. Pyranine is also used in yellow highlighters to provide their characteristic fluorescence and bright yellow-green colour. It is also found in some types of soap. Synthesis Pyranine is synthesized from pyrenetetrasulfonic acid and a solution of sodium hydroxide in water under reflux. The trisodium salt crystallizes as yellow needles when adding an aqueous solution of sodium chloride. See also * Fluorescein * Fluorescence Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colore ... References {{reflist External links CTD's Pyranine pagefrom the Compa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluoranthene
Fluoranthene is a polycyclic aromatic hydrocarbon (PAH). The molecule can be viewed as the fusion of naphthalene and benzene unit connected by a five-membered ring. The chemical formula is . Although samples are often pale yellow, the compound is colorless. It is soluble in nonpolar organic solvents.Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer, Hartmut Höke “Hydrocarbons” in Ullmann's Encyclopedia of Industrial Chemistry 2002 Wiley-VCH, Weinheim. It is a member of the class of PAHs known as non-alternant PAHs because it has rings other than those with six carbon atoms. It is a structural isomer of the alternant PAH pyrene. It is not as thermodynamically stable as pyrene. Its name is derived from its fluorescence under UV light. Occurrence Traces of fluoranthene is found in many combustion products, along with other PAHs. It results from incomplete combustion. Fluoranthene was originally isola ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzene
Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly Combustibility and flammability, flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a Precursor (chemistry), precursor to the manufacture of chemicals with more complex structures, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major Chemical industry, industrial che ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Excimer
An excimer (originally short for excited dimer) is a short-lived polyatomic molecule formed from two species that do not form a stable molecule in the ground state. In this case, formation of molecules is possible only if such atom is in an electronic excited state. Heteronuclear molecules and molecules that have more than two species are also called exciplex molecules (originally short for excited complex). Excimers are often diatomic and are composed of two atoms or molecules that would not bond if both were in the ground state. The lifetime of an excimer is very short, on the order of nanoseconds. Formation and decay Under the molecular orbital formalism, a typical ground-state molecule has electrons in the lowest possible energy levels. According to the Pauli principle, at most two electrons can occupy a given orbital, and if an orbital contains two electrons they must be in opposite spin states. The highest occupied molecular orbital is called the HOMO and the lowest uno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodor Förster
Theodor Förster (15 May 1910 – 20 May 1974) was a German Physical chemistry, physical chemist known for theoretical work on light-matter interaction in molecular systems such as fluorescence and Förster resonance energy transfer, resonant energy transfer. Education and career Förster was born in Frankfurt am Main and studied physics and mathematics at the University of Frankfurt am Main, University of Frankfurt from 1929 to 1933. He received his Ph.D. at the age of only 23 under Erwin Madelung in 1933. In the same year he joined the Nazi Party and the Sturmabteilung, SA. He then joined Karl-Friedrich Bonhoeffer as a research assistant at the Leipzig University, where he worked closely with Peter Debye, Werner Heisenberg, and Hans Kautzky. Förster obtained his habilitation in 1940 and became a lecturer at the Leipzig University. Following his research and teaching activities in Leipzig, he became a professor at the Poznań University in occupied Poland (1942). From 1947 to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
