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Sigmatropic reaction

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In organic chemistry, a sigmatropic reaction (from Greekτρόπος (trópos)'turn') is a pericyclic reaction wherein the net result is one sigma bond (σ-bond) is changed to another σ-bond in an intramolecular reaction. In this type of rearrangement reaction, a substituent moves from one part of a π-system to another part with simultaneous rearrangement of the π-system. True sigmatropic reactions are usually uncatalyzed, although Lewis acid catalysis is possible.

Rearrangement reactionRearrangement reactionIn organic chemistry, a rearrangement reaction is a broad class of organic reactions "that involves a change of connectivity". Usually the term rearrangement refers to intramolecular processes involving modification of carbon skeleton. Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular.Pericyclic reactionPericyclic reactionIn organic chemistry, a pericyclic reaction is the type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overlap in a continuous cycle at the transition state.Intramolecular reactionIntramolecular reactionIn chemistry, intramolecular describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule. Relative ratesIn intramolecular organic reactions, two reaction sites are contained within a single molecule. This configuration elevates the effective concentration of the reacting partners resulting in high reaction rates.Reaction intermediateReaction intermediateIn chemistry, a reaction intermediate, or intermediate, is a molecular entity arising within the sequence of a stepwise chemical reaction. It is formed as the reaction product of an elementary step, from the reactants and/or preceding intermediates, but is consumed in a later step. It does not appear in the chemical equation for the overall reaction.Conjugated systemConjugated systemIn physical organic chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represented as having alternating single and multiple bonds. Lone pairs, radicals or carbenium ions may be part of the system, which may be cyclic, acyclic, linear or mixed.SubstituentIn organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. The suffix -yl is used when naming organic compounds that contain a single bond replacing one hydrogen; -ylidene and -ylidyne are used with double bonds and triple bonds, respectively.CatalysisCatalysisCatalysis (, ) is the increase in rate of a chemical reaction due to an added substance known as a catalyst ( ). Catalysts are not consumed by the reaction and remain unchanged after the reaction. If the reaction is rapid and the catalyst is recycled quickly, a very small amount of catalyst often suffices; mixing, surface area, and temperature are important factors in reaction rate.Organic chemistryOrganic chemistryOrganic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials (i.e. matter in its various forms that contain carbonatoms). It involves studying the structure of organic material to determine the structural formula, analyzing physical and chemical properties, and evaluating chemical reactivity to understand the behavior of organic compounds.Lewis acid catalysisLewis acid catalysisIn organic chemistry, Lewis acid catalysis is the use of metal-based Lewis acids as catalysts for organic reactions. The acids act as an electron pair acceptor to increase the reactivity of a substrate. Common Lewis acid catalysts are based on main group metals such as aluminum, boron, silicon, and tin, as well as many early (titanium, zirconium) and late (iron, copper, zinc) d-block metals.Sigma bondSigma bondIn chemistry, sigma bonds (σ bonds) or sigma overlap are the strongest type of covalentchemical bond. They are formed by head-on overlapping between atomic orbitals along the internuclear axis. Sigma bonding is most simply defined for diatomic molecules using the language and tools of symmetry groups. In this formal approach, a σ-bond is symmetrical with respect to rotation about the bond axis.Transition metalTransition metalIn chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinide elements (the f-block) are called inner transition metals and are sometimes considered to be transition metals as well. They are lustrous metals with good electrical and thermal conductivity.Greek languageGreek languageGreek (Modern Greek: ελληνικά, romanized: elliniká; Ancient Greek: ἑλληνική, romanized: hellēnikḗ) is an Indo-European language, constituting an independent Hellenic branch within the Indo-European language family. It is native to the territories that have had populations of Greeks since antiquity: Greece, Cyprus, Egypt, Turkey, Italy (in Calabria and Salento), southern Albania, and other regions of the Balkans, Caucasus, the Black Sea coast, and the .migrationmigrationRelated word or term.

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