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Inverse Electron-demand Diels–Alder Reaction
The inverse electron demand Diels–Alder reaction, or DAINV or IEDDA is an organic chemical reaction, in which two new chemical bonds and a six-membered ring are formed. It is related to the Diels–Alder reaction, but unlike the Diels–Alder (or DA) reaction, the DAINV is a cycloaddition between an electron-rich dienophile and an electron-poor diene. During a DAINV reaction, three pi-bonds are broken, and two sigma bonds and one new pi-bond are formed. A prototypical DAINV reaction is shown on the right. DAINV reactions often involve heteroatoms, and can be used to form heterocyclic compounds. This makes the DAINV reaction particularly useful in natural product syntheses, where the target compounds often contain heterocycles. Recently, the DAINV reaction has been used to synthesize a drug transport system which targets prostate cancer. History The Diels–Alder reaction was first reported in 1928 by Otto Diels and Kurt Alder; they were awarded the Nobel Prize in che ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frontier Molecular Orbital Theory
In chemistry, frontier molecular orbital theory is an application of MO theory describing HOMO/LUMO interactions. History In 1952, Kenichi Fukui published a paper in the ''Journal of Chemical Physics'' titled "A molecular theory of reactivity in aromatic hydrocarbons." Though widely criticized at the time, he later shared the Nobel Prize in Chemistry with Roald Hoffmann for his work on reaction mechanisms. Hoffman's work focused on creating a set of four pericyclic reactions in organic chemistry, based on orbital symmetry, which he coauthored with Robert Burns Woodward, entitled "The Conservation of Orbital Symmetry." Fukui's own work looked at the frontier orbitals, and in particular the effects of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital ( LUMO) on reaction mechanisms, which led to it being called Frontier Molecular Orbital Theory (FMO Theory). He used these interactions to better understand the conclusions of the Woodward–Ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Orbital Diagram
A molecular orbital diagram, or MO diagram, is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the linear combination of atomic orbitals (LCAO) method in particular. A fundamental principle of these theories is that as atoms bond to form molecules, a certain number of atomic orbitals combine to form the same number of molecular orbitals, although the electrons involved may be redistributed among the orbitals. This tool is very well suited for simple diatomic molecules such as dihydrogen, dioxygen, and carbon monoxide but becomes more complex when discussing even comparatively simple polyatomic molecules, such as methane. MO diagrams can explain why some molecules exist and others do not. They can also predict bond strength, as well as the electronic transitions that can take place. History Qualitative MO theory was introduced in 1928 by Robert S. Mulliken and Friedrich Hund. A mathematical description w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarafacial And Suprafacial
Antarafacial ( Woodward-Hoffmann symbol a) and suprafacial (s) are two topological concepts in organic chemistry describing the relationship between two simultaneous chemical bond making and/or bond breaking processes in or around a reaction center. The reaction center can be a p- or sp''n-''orbital (Woodward-Hoffmann symbol ω), a conjugated system (π) or even a sigma bond (σ). * The relationship is ''antarafacial'' when opposite faces of the π system or isolated orbital are involved in the process (think ''anti''). For a σ bond, it corresponds to involvement of one "interior" lobe and one "exterior" lobe of the bond. * The relationship is ''suprafacial'' when the same face of the π system or isolated orbital are involved in the process (think ''syn''). For a σ bond, it corresponds to involvement of two "interior" lobes or two "exterior" lobes of the bond. The components of all pericyclic reactions, including sigmatropic reactions and cycloadditions, and electrocycliza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suprafacial
Antarafacial ( Woodward-Hoffmann symbol a) and suprafacial (s) are two topological concepts in organic chemistry describing the relationship between two simultaneous chemical bond making and/or bond breaking processes in or around a reaction center. The reaction center can be a p- or sp''n-''orbital (Woodward-Hoffmann symbol ω), a conjugated system (π) or even a sigma bond (σ). * The relationship is ''antarafacial'' when opposite faces of the π system or isolated orbital are involved in the process (think ''anti''). For a σ bond, it corresponds to involvement of one "interior" lobe and one "exterior" lobe of the bond. * The relationship is ''suprafacial'' when the same face of the π system or isolated orbital are involved in the process (think ''syn''). For a σ bond, it corresponds to involvement of two "interior" lobes or two "exterior" lobes of the bond. The components of all pericyclic reactions, including sigmatropic reactions and cycloadditions, and electrocyclizatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woodward–Hoffmann Rules
The Woodward–Hoffmann rules (or the pericyclic selection rules), devised by Robert Burns Woodward and Roald Hoffmann, are a set of rules used to rationalize or predict certain aspects of the stereochemistry and activation energy of pericyclic reactions, an important class of reactions in organic chemistry. The rules are best understood in terms of the concept of ''the conservation of orbital symmetry'' using ''orbital correlation diagrams'' (see Section 3 below). The Woodward–Hoffmann rules are a consequence of the changes in electronic structure that occur during a pericyclic reaction and are predicated on the phasing of the interacting molecular orbitals. They are applicable to all classes of pericyclic reactions (and their microscopic reverse 'retro' processes), including (1) electrocyclizations, (2) cycloadditions, (3) sigmatropic reactions, (4) group transfer reactions, (5) ene reactions, (6) cheletropic reactions, and (7) dyotropic reactions. Due to their elegance, simp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boat Ts For MVE And Acrolein
A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inland waterways such as rivers and lakes, or in protected coastal areas. However, some boats, such as the whaleboat, were intended for use in an offshore environment. In modern naval terms, a boat is a vessel small enough to be carried aboard a ship. Boats vary in proportion and construction methods with their intended purpose, available materials, or local traditions. Canoes have been used since prehistoric times and remain in use throughout the world for transportation, fishing, and sport. Fishing boats vary widely in style partly to match local conditions. Pleasure craft used in recreational boating include ski boats, pontoon boats, and sailboats. House boats may be used for vacationing or long-term residence. Lighters are used to conve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Density Functional Theory
Density-functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals, i.e. functions of another function. In the case of DFT, these are functionals of the spatially dependent electron density. DFT is among the most popular and versatile methods available in condensed-matter physics, computational physics, and computational chemistry. DFT has been very popular for calculations in solid-state physics since the 1970s. However, DFT was not considered accurate enough for calculations in quantum chemistry until the 1990s, when the approximations used in the theory were greatly refined to better model the exchange and correlation interactions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition State
In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked with the double dagger ‡ symbol. As an example, the transition state shown below occurs during the SN2 reaction of bromoethane with a hydroxide anion: The activated complex of a reaction can refer to either the transition state or to other states along the reaction coordinate between reactants and products, especially those close to the transition state. Peter Atkins and Julio de Paula, ''Physical Chemistry'' (8th ed., W.H. Freeman 2006), p.809 According to the transition state theory, once the reactants have passed through the transition state configuration, they always continue to form products. History of concept The concept of a transition state has been important in many theories of the rates at which chemical reactio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methyl Vinyl Ether
Methyl vinyl ether is an organic compound with the chemical formula CH3OCH=CH2. A colorless gas, it is the simplest enol ether. It is used as a synthetic building block, as is the related compound ethyl vinyl ether (a liquid at room temperature). Preparation Methyl vinyl ether can be made by reaction of acetylene and methanol in presence of a base. Reactions The alkene portion of the molecule is reactive in many ways. It is prone to polymerization, leading to formation of polyvinyl ethers. Polymerization is typically initiated with Lewis acids such as boron trifluoride. This mode of reactivity is analogous to the way vinyl acetate and vinyl chloride can be polymerized to form polyvinyl acetate and polyvinyl chloride, respectively. Methyl vinyl ether also participates in +2cycloaddition reactions. Its reaction with acrolein is the first step in the commercial synthesis of glutaraldehyde. The alkene can be deprotonated at the vinyl carbon adjacent to the oxygen. In particu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
