Search results
Results from the WOW.Com Content Network
A carbanion is one of several reactive intermediates in organic chemistry. In organic synthesis, organolithium reagents and Grignard reagents are commonly treated and referred to as "carbanions." This is a convenient approximation, although these species are generally clusters or complexes containing highly polar, but still covalent bonds metal ...
In chemistry, a nonclassical ion usually refers to carbonium ions, a family of organic cations. They are characterized by delocalized three-center, two-electron bonds . The more stable members are often bi- or polycyclic.
Main page; Contents; Current events; Random article; About Wikipedia; Contact us
The Horner–Wadsworth–Emmons (HWE) reaction is a chemical reaction used in organic chemistry of stabilized phosphonate carbanions with aldehydes (or ketones) to produce predominantly E-alkenes. [1] The Horner–Wadsworth–Emmons reaction. In 1958, Leopold Horner published a modified Wittig reaction using phosphonate-stabilized carbanions.
Substitution reactions in organic chemistry are classified either as electrophilic or nucleophilic depending upon the reagent involved, whether a reactive intermediate involved in the reaction is a carbocation, a carbanion or a free radical, and whether the substrate is aliphatic or aromatic. Detailed understanding of a reaction type helps to ...
Two equivalents of strong base such as n-butyllithium abstract the proton from the hydrazone (4) followed by the less acidic proton α to the hydrazone carbon (5), forming a carbanion. The carbanion then undergoes. an elimination reaction producing a carbon–carbon double bond and ejecting the tosyl anion, forming a diazonium anion (6).
When the α-silyl carbanion contains only alkyl, hydrogen, or electron-donating substituents, the stereochemical outcome of the Peterson olefination can be controlled, [7] because at low temperature the elimination is slow and the intermediate β-hydroxysilane can be isolated. Once isolated, the diastereomeric β-hydroxysilanes are separated.
The 2-norbornyl cation is one of the best characterized carbonium ion. It is the prototype for non-classical ions. As indicated first by low-temperature NMR spectroscopy and confirmed by X-ray crystallography, [1] it has a symmetric structure with an RCH 2 + group bonded to an alkene group, stabilized by a bicyclic structure.