Fischer Carbene
A Fischer carbene is a divalent organic ligand in an organometallic compound. In a Fischer carbene, the carbene ligand is a σ-donor π-acceptor ligand. Because π-backdonation from the metal centre is generally weak, the carbene carbon is electrophilic. Fischer carbenes are named for Ernst Otto Fischer. Structure A metal carbene complex could be considered a Fischer carbene when the carbene is in singlet state. Delocalization of the lone pair from the substituent on carbene carbon raises the energy of pz orbital, thus forcing the two of electrons of carbene stay as an electron pair. Bonding between carbene and the metal centre involves a strong σ donation from sp2 orbital to an empty d orbital on metal centre and a weak π back donation from the metal centre to the empty pz orbital. Because the π donation is weak, the carbene carbon is electrophilic in nature. Because of this bonding property, Fischer carbenes often feature: # low oxidation state metal center # middle an ...
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Carbene
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms. The term "carbene" may also refer to the specific compound , also called methylene, the parent hydride from which all other carbene compounds are formally derived. Carbenes are classified as either singlets or triplets, depending upon their electronic structure. Most carbenes are very short lived, although persistent carbenes are known. One well-studied carbene is dichlorocarbene , which can be generated ''in situ'' from chloroform and a strong base. Structures and bonding The two classes of carbenes are singlet and triplet carbenes. Singlet carbenes are spin-paired. In the language of valence bond theory, the molecule adopts an sp2 hybrid structure. Triplet carbenes have two unpaired electrons. Most carbenes have a nonlinear triplet ground state, e ...
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Reactivity 1
Reactivity may refer to: * Reactivity (chemistry), the rate at which a chemical substance tends to undergo a chemical reaction * Reactive programming, a property of an execution model whereby changes are automatically propagated through a dataflow network * Reactivity (psychology) * Reactivity (electronics) * Reactivity of a nuclear reactor See also * Reactive (other) * Reactance (other) Reactance may refer to: * Electrical reactance, the opposition to a change in voltage due to capacitance (capacitive reactance) or in current due to inductance (inductive reactance); the imaginary component of AC impedance * Magnetic reactance, a s ...

Wulff–Dötz Reaction
The Wulff–Dötz reaction (also known as the Dötz reaction or the benzannulation reaction of the Fischer carbene complexes) is the chemical reaction of an aromatic or vinylic alkoxy pentacarbonyl chromium carbene complex with an alkyne and carbon monoxide to give a Cr(CO)3-coordinated substituted phenol. Several reviews have been published. It is named after the German chemist Karl Heinz Dötz (b. 1943) and the American chemist William D. Wulff (b. 1949) at Michigan State University. The reaction was first discovered by Karl Dötz and was extensively developed by his group and W. Wulff's group. They subsequently share the name of the reaction. The position of the substituents is highly predictable with the largest alkyne substituent (RL) neighboring the phenol and the smallest alkyne substituent (RS) neighboring the methoxy group. Hence, this reaction is more useful for terminal alkynes than internal alkynes. The phenol can be liberated from the chromium complex by a mild oxi ...
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Orbital Diagram
Orbital may refer to: Sciences Chemistry and physics * Atomic orbital * Molecular orbital * Hybrid orbital Astronomy and space flight * Orbit ** Earth orbit Medicine and physiology * Orbit (anatomy), also known as the ''orbital bone'' * Orbitofrontal cortex, a part of the brain used for decision making Business * Orbital Corporation, an Australian engine technology company * Orbital Sciences Corporation, a U.S. satellite launch and defense systems corporation * Orbital ATK, American aerospace manufacturer formed from the merger of Orbital Sciences Corporation and parts of Alliant Techsystems Transportation * Ring road (or ''orbital road'' in some regions) * Orbital (metro), a rapid transit line usually encircling a city centre * Orbital engine Other uses * Orbital (The Culture), artificial worlds from Iain M. Banks's series of science fiction novels, the Culture * Orbital (band), an English electronic dance music duo ** ''Orbital'' (1991 album) ** ''Orbital'' (1993 album) ...
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Migratory Insertion
In organometallic chemistry, a migratory insertion is a type of reaction wherein two ligands on a metal complex combine. It is a subset of reactions that very closely resembles the insertion reactions, and both are differentiated by the mechanism that leads to the resulting stereochemistry of the products. However, often the two are used interchangeably because the mechanism is sometimes unknown. Therefore, migratory insertion reactions or insertion reactions, for short, are defined not by the mechanism but by the overall regiochemistry wherein one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.: : + \longrightarrow Overview In the migratory insertion, a ligand that is viewed as an anion (X) ligand in and a ligand that is viewed as neutral couple, generating a new anionic ligand. The anion and neutral ligands that react are adjacent. If the precursor complex is coordinatively saturated, migratory insertion often result in a co ...
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Ultraviolet–visible Spectroscopy
UV spectroscopy or UV–visible spectrophotometry (UV–Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible regions of the electromagnetic spectrum. Being relatively inexpensive and easily implemented, this methodology is widely used in diverse applied and fundamental applications. The only requirement is that the sample absorb in the UV-Vis region, i.e. be a chromophore. Absorption spectroscopy is complementary to fluorescence spectroscopy. Parameters of interest, besides the wavelength of measurement, are absorbance (A) or transmittance (%T) or reflectance (%R), and its change with time. Optical transitions Most molecules and ions absorb energy in the ultraviolet or visible range, i.e., they are chromophores. The absorbed photon excites an electron in the chromophore to higher energy molecular orbitals, giving rise to an excited state. For organic chromophores, four possible types of transitions ...
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Dem 2
Dem 2 is the name of UK garage musician Dean Boylan. They were originally a duo which consisted of Boylan and Spencer Edwards, who are from Thurrock in Essex. Since 2011, Boylan continued releasing material under the Dem 2 moniker as a solo artist. The duo founded the record label New York Soundclash Records in 1994 and released the 12" vinyl "Reach". They are best known for the songs "Destiny", "Baby (You're So Sexy)" and Da Grunge Mix of "All I Know", released under the alias U.S. Alliance. "Destiny" was a hit single in 1998, reaching No. 58 on the UK Singles Chart and No. 1 on the UK Dance Singles Chart. Alexis Petridis, writing for ''The Guardian'' in 2019, looking back at the genre after 20 years, listed "Destiny" at number 13 in his list of his 20 best UK garage tracks. Simon Reynolds, writing in ''The Wire ''The Wire'' is an American Crime film, crime drama Television show, television series created and primarily written by author and former police reporter David Si ...
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Dem 1
DEM was the ISO 4217 currency code for the Deutsche Mark, former currency of Germany Computing * Digital elevation model, a digital representation of ground-surface topography or terrain ** .dem, a common extension for USGS DEM files * Discrete element method or discrete element modeling, a family of numerical methods for computing the motion of a large number of small particles (like molecules or grains of sand) * Diffuse element method, a numerical simulation method used (for example) to solve partial differential equations * Display Encode Mode, a feature of the AMD's Video Codec Engine * Distance Estimation Method, for drawing Julia sets or Mandelbrot sets Organisations * Department of Environmental Management, a name of various government entities * Democratic Party, short form of the name of the political parties in the world * Democratic Party (United States) * Democrats (Brazil) * Dravske elektrarne Maribor d.o.o., an electric power company in Slovenia * Day Eight ...
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Reactivity 5
Reactivity may refer to: * Reactivity (chemistry), the rate at which a chemical substance tends to undergo a chemical reaction * Reactive programming, a property of an execution model whereby changes are automatically propagated through a dataflow network * Reactivity (psychology) * Reactivity (electronics) * Reactivity of a nuclear reactor See also * Reactive (other) * Reactance (other) Reactance may refer to: * Electrical reactance, the opposition to a change in voltage due to capacitance (capacitive reactance) or in current due to inductance (inductive reactance); the imaginary component of AC impedance * Magnetic reactance, a s ...

Reactivity 4
Reactivity may refer to: * Reactivity (chemistry), the rate at which a chemical substance tends to undergo a chemical reaction * Reactive programming, a property of an execution model whereby changes are automatically propagated through a dataflow network * Reactivity (psychology) * Reactivity (electronics) * Reactivity of a nuclear reactor See also * Reactive (other) * Reactance (other) Reactance may refer to: * Electrical reactance, the opposition to a change in voltage due to capacitance (capacitive reactance) or in current due to inductance (inductive reactance); the imaginary component of AC impedance * Magnetic reactance, a s ...

Michael Addition
In organic chemistry, the Michael reaction or Michael addition is a reaction between a Michael donor (an enolate or other nucleophile) and a Michael acceptor (usually an α,β-unsaturated carbonyl) to produce a Michael adduct by creating a carbon-carbon bond at the acceptor's β-carbon. It belongs to the larger class of conjugate additions and is widely used for the mild formation of carbon-carbon bonds. The Michael addition is an important atom-economical method for diastereoselective and enantioselective C–C bond formation, and many asymmetric variants exist : In this general Michael addition scheme, either or both of R and R' on the nucleophile (the Michael donor) represent electron-withdrawing substituents such as acyl, cyano, nitro, or sulfone groups, which make the adjacent methylene hydrogen acidic enough to form a carbanion when reacted with the base, ''B:''. For the alkene (the Michael acceptor), the R" substituent is usually a carbonyl, which makes the compound ...
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