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In electrophilic substitution in aromatic compounds, an atom appended to the aromatic ring, usually hydrogen, is replaced by an electrophile.The most important reactions of this type that take place are aromatic nitration, aromatic halogenation, aromatic sulfonation and acylation and alkylating Friedel-Crafts reactions.
Electrophilic aromatic substitution (S E Ar) 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 ...
Steric inhibition of protonation caused by substitution of anilines to become weaker bases, compared to substitution of isomers in the meta and para position. Electrophilic aromatic substitution of disubstituted benzene compounds causes steric effects which determines the regioselectivity of an incoming electrophile in disubstituted benzene ...
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 ...
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.
Activating substituents favour electrophilic substitution about the ortho and para positions. Weakly deactivating groups direct electrophiles to attack the benzene molecule at the ortho- and para- positions, while strongly and moderately deactivating groups direct attacks to the meta- position. [ 5 ]
Sulfur trioxide or its protonated derivative is the actual electrophile in this electrophilic aromatic substitution. To drive the equilibrium, dehydrating agents such as thionyl chloride can be added: [2] C 6 H 6 + H 2 SO 4 + SOCl 2 → C 6 H 5 SO 3 H + SO 2 + 2 HCl. Historically, mercurous sulfate has been used to catalyze the reaction. [3]
Pyrrole electrophilic substitution. Pyrroles react easily with nitrating (e.g. HNO 3 /Ac 2 O), sulfonating (Py·SO 3), and halogenating (e.g. NCS, NBS, Br 2, SO 2 Cl 2, and KI/H 2 O 2) agents. [31] Halogenation generally provides polyhalogenated pyrroles, but monohalogenation can be performed.