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Criegee Biradical
A Criegee intermediate (also called a Criegee zwitterion or Criegee biradical) is a carbonyl oxide with two charge centres. These chemicals may react with sulfur dioxide and nitrogen oxides in the earth's atmosphere, and are implicated in the formation of aerosols, which are an important factor in controlling global climate. Criegee intermediates are also an important source of OH (hydroxyl radicals). OH radicals are the most important oxidant in the troposphere, and are important in controlling air quality and pollution. The formation of this sort of structure was first postulated in the 1950s by Rudolf Criegee, for whom it is named. It was not until 2012 that direct detection of such chemicals was reported. Infrared spectroscopy suggests the electronic structure has a substantially zwitterionic character rather than the biradical character that had previously been proposed. Formation Criegee intermediates are formed by the gas-phase reactions of alkenes and ozone in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonyl Oxide (Criegee Zwitterion)
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl). The remainder of this article concerns itself with the organic chemistry definition of carbonyl, where carbon and oxygen share a double bond. Carbonyl compounds In organic chemistry, a carbonyl group characterizes the following types of compounds: Other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. Examples of inorganic carbonyl compounds are carbon dioxide and carbonyl sulfide. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared Spectroscopy
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer (or spectrophotometer) which produces an infrared spectrum. An IR spectrum can be visualized in a graph of infrared light absorbance (or transmittance) on the vertical axis vs. frequency, wavenumber or wavelength on the horizontal axis. Typical units of wavenumber used in IR spectra are reciprocal centimeters, with the symbol cm−1. Units of IR wavelength are commonly given in micrometers (formerly called "microns"), symbol μm, which are related to the wavenumber in a reciprocal way. A com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Bonding
A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding. Strong chemical bonding arises from the sharing or transfer of electrons between the participating atoms. Since opposite electric charges attract, the negatively charged electrons surrounding the nucleus and the positively charged protons within a nucleus attract each other. An electron positioned between two nuclei will be attracted to both of them, and the nuclei will be attracted toward electrons in this position. This attraction constitutes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Radicals
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (꞉) which have two unpaired electrons. Radicals may be generated in a number of ways, but typical methods involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are known to produce radicals. Radicals are intermediates in many chemical reactions, more so than is apparent from the balanced equations. Radicals are important in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. A majority of n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ozonide
Ozonide is the polyatomic anion . Cyclic organic compounds formed by the addition of ozone () to an alkene are also called ozonides. Ionic ozonides Inorganic ozonides are dark red salts. The anion has the bent shape of the ozone molecule. Inorganic ozonides are formed by burning potassium, rubidium, or caesium in ozone, or by treating the alkali metal hydroxide with ozone; this yields potassium ozonide, rubidium ozonide, and caesium ozonide respectively. They are very sensitive explosives that have to be handled at low temperatures in an atmosphere consisting of an inert gas. Lithium and sodium ozonide are extremely labile and must be prepared by low-temperature ion exchange starting from . Sodium ozonide, , which is prone to decomposition into NaOH and , was previously thought to be impossible to obtain in pure form. However, with the help of cryptands and methylamine, pure sodium ozonide may be obtained as red crystals isostructural to . Ionic ozonides are being investigate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bond C=O). The simplest ketone is acetone (where R and R' is methyl), with the formula . Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids (e.g., testosterone), and the solvent acetone. Nomenclature and etymology The word ''ketone'' is derived from ''Aketon'', an old German word for ''acetone''. According to the rules of IUPAC nomenclature, ketone names are derived by changing the suffix ''-ane'' of the parent alkane to ''-anone''. Typically, the position of the carbonyl group is denoted by a number, but traditional nonsystematic names are still generally used for the most important ketones, for example acetone and benzophenone. These nonsystematic names are considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and play important roles in the technology and biological spheres. Structure and bonding Aldehydes feature a carbon center that is connected by a double bond to oxygen and a single bond to hydrogen and single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen. The central carbon is often described as being sp2- hybridized. The aldehyde group is somewhat polar. The C=O bond length is about 120-122 picometers. Physical properties and characterization Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile aldehydes have pungent odors. Al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molozonide
A molozonide (or "molecular ozonide") is a 1,2,3-trioxolane, which can also be thought of a cyclic dialkyl trioxidane. Molozonides are formed by cycloaddition of ozone and an alkene during ozonolysis, as a transient intermediate which quickly rearranges to give the ozonide Ozonide is the polyatomic anion . Cyclic organic compounds formed by the addition of ozone () to an alkene are also called ozonides. Ionic ozonides Inorganic ozonides are dark red salts. The anion has the bent shape of the ozone molecule. Inor ... (1,2,4-trioxolane), the relatively stable product generated immediately prior to reductive or oxidative cleavage to form alcohols, carbonyl compounds, or derivatives thereof. References Oxygen heterocycles Polyoxides Heterocyclic compounds with 1 ring {{Heterocyclic-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ozonolysis CarbonylOxide Formation
In organic chemistry, ozonolysis is an organic reaction where the unsaturated bonds of alkenes (), alkynes (), or azo compounds () are cleaved with ozone (). Alkenes and alkynes form organic compounds in which the multiple carbon–carbon bond has been replaced by a carbonyl () group while azo compounds form nitrosamines (). The outcome of the reaction depends on the type of multiple bond being oxidized and the work-up conditions. Ozonolysis of alkenes Alkenes can be oxidized with ozone to form alcohols, aldehydes or ketones, or carboxylic acids. In a typical procedure, ozone is bubbled through a solution of the alkene in methanol at −78 °C until the solution takes on a characteristic blue color, which is due to unreacted ozone. This indicates complete consumption of the alkene. Alternatively, various other chemicals can be used as indicators of this endpoint by detecting the presence of ozone. If ozonolysis is performed by bubbling a stream of ozone-enriched o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Structure
In quantum chemistry, electronic structure is the state of motion of electrons in an electrostatic field created by stationary nuclei. The term encompasses both the wave functions of the electrons and the energies associated with them. Electronic structure is obtained by solving quantum mechanical equations for the aforementioned clamped-nuclei problem. Electronic structure problems arise from the Born–Oppenheimer approximation. Along with nuclear dynamics, the electronic structure problem is one of the two steps in studying the quantum mechanical motion of a molecular system. Except for a small number of simple problems such as hydrogen-like atoms, the solution of electronic structure problems require modern computers. Electronic structure problem is routinely solved with quantum chemistry computer programs. Electronic structure calculations rank among the most computationally intensive tasks in all scientific calculations. For this reason, quantum chemistry calculatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science Daily
''Science Daily'' is an American website launched in 1995 that aggregates press releases and publishes lightly edited press releases (a practice called churnalism) about science, similar to Phys.org and EurekAlert!. The site was founded by married couple Dan and Michele Hogan in 1995; Dan Hogan formerly worked in the public affairs department of Jackson Laboratory writing press releases. The site makes money from selling advertisements. As of 2010, the site said that it had grown "from a two-person operation to a full-fledged news business with worldwide contributors". At the time, it was run out of the Hogans' home, had no reporters, and only reprinted press releases. In 2012, Quantcast Quantcast is an American technology company, founded in 2006, that specializes in AI-driven real-time advertising, audience insights and measurement. It has offices in the United States, Canada, Australia, Singapore, United Kingdom, Ireland, Fran ... ranked it at 614 with 2.6 million U.S. vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zwitterion
In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively-charged functional groups. : With amino acids, for example, in solution a chemical equilibrium will be established between the "parent" molecule and the zwitterion. Betaines are zwitterions that cannot isomerize to an all-neutral form, such as when the positive charge is located on a quaternary ammonium group. Similarly, a molecule containing a phosphonium group and a carboxylate group cannot isomerize. Amino acids The equilibrium is established in two stages. In the first stage, a proton is transferred from the carboxyl group to a water molecule: :H2N(R)CO2H + H2O H2N(R)CO2- + H3O+ In the second stage, a proton is transferred from the hydronium ion to the amine group: :H2N(R)CO2- + H3O+ H3N+ (R)CO2- + H2O Overall, the reaction is an isomerization reaction :H2N(R)CO2H H3N+ (R)CO2- The ratio of the concentrations of the two spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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