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Electrophilic aromatic substitution (SEAr) is an organic reaction in which an atom that is attached to an aromatic system (usually hydrogen) is replaced by an electrophile. Some of the most important electrophilic aromatic substitutions are aromatic nitration, aromatic halogenation, aromatic sulfonation, alkylation Friedel–Crafts reaction and ...
Electrophilic aromatic directing groups. In electrophilic aromatic substitution reactions, existing substituent groups on the aromatic ring influence the overall reaction rate or have a directing effect on positional isomer of the products that are formed. An electron donating group (EDG) or electron releasing group (ERG, Z in structural ...
Ipso-substitution describes two substituents sharing the same ring position in an intermediate compound in an electrophilic aromatic substitution. Trimethylsilyl, tert-butyl, and isopropyl groups can form stable carbocations, hence are ipso directing groups. Meso-substitution refers to the substituents occupying a benzylic position.
Hammett equation. In organic chemistry, the Hammett equation describes a linear free-energy relationship relating reaction rates and equilibrium constants for many reactions involving benzoic acid derivatives with meta- and para- substituents to each other with just two parameters: a substituent constant and a reaction constant. [1][2] This ...
Ortho effect is an organic chemistry phenomenon where the presence of a chemical group at the at ortho position or the 1 and 2 position of a phenyl ring, relative to the carboxylic compound changes the chemical properties of the compound. This is caused by steric effects and bonding interactions along with polar effects caused by the various ...
Electrophilic substitution. Electrophilic substitution reactions are chemical reactions in which an electrophile displaces a functional group in a compound, which is typically, but not always, aromatic. Aromatic substitution reactions are characteristic of aromatic compounds and are common ways of introducing functional groups into benzene rings.
Taking the well-known Friedel–Craft electrophilic aromatic substitution as example, electron donating groups direct the electrophile to ortho-/para-position while electron withdrawing groups direct the electrophile to meta-position. However, with complicated systems, electronic difference between different C–H bonds can be subtle and ...
Directed ortho metalation. Directed ortho metalation (DoM) is an adaptation of electrophilic aromatic substitution in which electrophiles attach themselves exclusively to the ortho- position of a direct metalation group or DMG through the intermediary of an aryllithium compound. [1] The DMG interacts with lithium through a hetero atom.