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In organic chemistry, a sigmatropic reaction (from Greek τρόπος (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. [1]
In chemistry, sigma bonds (σ bonds) or sigma overlap are the strongest type of covalent chemical bond. [1] 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 ...
Sigma complexes are of great mechanistic significance, despite their frequent fragility. They represent an initial interaction between the metal center and a hydrocarbon substrate. As such, sigma complexes are generally assumed to be intermediates prior to full oxidative addition .
In chemistry, sigma hole interactions (or σ-hole interactions) are a family of intermolecular forces that can occur between several classes of molecules and arise from an energetically stabilizing interaction between a positively-charged site, termed a sigma hole, and a negatively-charged site, typically a lone pair, on different atoms that are not covalently bonded to each other. [1]
Today, it is known as lunate sigma (uppercase Ϲ, lowercase ϲ), because of its crescent-like shape, and is still widely used in decorative typefaces in Greece, especially in religious and church contexts, as well as in some modern print editions of classical Greek texts.
We all had different favorite subjects at school that we wanted to have more classes in. Chemistry is a controversial one because some people absolutely loved it and some really hated it. Whether ...
What does ‘sigma’ mean? ... Another definition for “sigma” says Lindsay, is “the best.” “Kids use Alpha and Sigma interchangeably,” Lindsay tells TODAY.com. “They don’t make ...
Erich Hückel proposed a representation of the double bond as a combination of a sigma bond plus a pi bond. [7] [8] [9] The σ-π representation is the better-known one, and it is the one found in most textbooks since the late-20th century.