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In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. [1] Because electrophiles accept electrons, they are Lewis acids . [ 2 ] Most electrophiles are positively charged , have an atom that carries a partial positive charge, or have an atom that does not have an octet of electrons.
For example, NH 3 is a Lewis base, because it can donate its lone pair of electrons. Trimethylborane [(CH 3 ) 3 B] is a Lewis acid as it is capable of accepting a lone pair. In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. [ 1 ]
An example of a substitution reaction taking place by a so-called borderline mechanism as originally studied by Hughes and Ingold [6] is the reaction of 1-phenylethyl chloride with sodium methoxide in methanol. The reaction rate is found to the sum of S N 1 and S N 2 components with 61% (3,5 M, 70 °C) taking place by the latter.
In general, in a group across the periodic table, the more basic the ion (the higher the pK a of the conjugate acid) the more reactive it is as a nucleophile. Within a series of nucleophiles with the same attacking element (e.g. oxygen), the order of nucleophilicity will follow basicity.
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.
In organic chemistry, an azo coupling is an reaction between a diazonium compound (R−N≡N +) and another aromatic compound that produces an azo compound (R−N=N−R’).In this electrophilic aromatic substitution reaction, the aryldiazonium cation is the electrophile, and the activated carbon (usually from an arene, which is called coupling agent), serves as a nucleophile.
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The most widely practised example of this reaction is the ethylation of benzene. Approximately 24,700,000 tons were produced in 1999. [2] (After dehydrogenation and polymerization, the commodity plastic polystyrene is produced.) In this process, acids are used as catalyst to generate the incipient carbocation. Many other electrophilic reactions ...