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Electrophilic substitution

 

 
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Electrophilic substitution
 
 
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Electrophilic substitution reactions are chemical reactions in which an electrophile
Electrophile

In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to Chemical bond to a nucleophile....
 displaces another group, typically but not always hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
. Electrophilic substitution is characteristic of aromatic compounds. Electrophilic aromatic substitution
Electrophilic aromatic substitution

Electrophilic aromatic substitution or EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic ring is replaced by an electrophile....
 is an important way of introducing functional groups on benzene
Benzene

Benzene, or benzol, is an organic compound chemical compound and a known carcinogen with the molecular formula Carbon6Hydrogen6....
 rings. The other main reaction type is electrophilic aliphatic substitution.

Electrophilic aliphatic substitution In electrophilic substitution in aliphatic compounds, an electrophile
Electrophile

In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to Chemical bond to a nucleophile....
 displaces a functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
.






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Electrophilic substitution reactions are chemical reactions in which an electrophile
Electrophile

In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to Chemical bond to a nucleophile....
 displaces another group, typically but not always hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
. Electrophilic substitution is characteristic of aromatic compounds. Electrophilic aromatic substitution
Electrophilic aromatic substitution

Electrophilic aromatic substitution or EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic ring is replaced by an electrophile....
 is an important way of introducing functional groups on benzene
Benzene

Benzene, or benzol, is an organic compound chemical compound and a known carcinogen with the molecular formula Carbon6Hydrogen6....
 rings. The other main reaction type is electrophilic aliphatic substitution.

Electrophilic aromatic substitution


The most important reactions of this type that take place are aromatic nitration, aromatic halogenation, aromatic sulfonation
Aromatic sulfonation

Aromatic sulfonation is an organic reaction in which a hydrogen atom on an aromatic hydrocarbon is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution....
 and acylation and alkylating Friedel-Crafts reaction
Friedel-Crafts reaction

The Friedel-Crafts reactions are a set of organic reaction developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel-Crafts reactions: alkylation reactions and acylation reactions....
s.

Electrophilic aliphatic substitution

In electrophilic substitution in aliphatic compounds, an electrophile
Electrophile

In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to Chemical bond to a nucleophile....
 displaces a functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
. This reaction is similar to nucleophilic aliphatic substitution where the reactant is a nucleophile
Nucleophile

In chemistry, a nucleophile is a reagent that forms a chemical bond to its reaction partner by donating both bonding electrons. Because nucleophiles donate electrons, they are by definition Lewis bases ....
 rather than an electrophile
Electrophile

In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to Chemical bond to a nucleophile....
. The two electrophilic reaction mechanisms, SE1 and SE2 (Substitution Electrophilic), are also similar to the nucleophile counterparts SN1 and SN2. In the SE1 course of action the substrate first ionizes into a carbanion
Carbanion

A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons ....
 and a positively charged organic residue. The carbanion then quickly recombines with the electrophile
Electrophile

In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to Chemical bond to a nucleophile....
. The SE2 reaction mechanism has a single transition state
Transition state

The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate....
 in which the old bond and the newly formed bond are both present.

Electrophilic aliphatic substitution reactions are:
  • Nitrosation
    Nitrosation

    Nitrosation is a process of converting organic compounds into nitroso derivatives, i.e. compounds containing the R-NO functionality....
  • Ketone halogenation
    Ketone halogenation

    In organic chemistry ketone halogenation is a special type of halogenation.The position alpha to the carbonyl group in a ketone is easily halogenated, due to the ability to form an enolate anion in basic solution, or an enol in acidic solution....
  • Keto-enol tautomerism
    Keto-enol tautomerism

    In organic chemistry, keto-enol tautomerism refers to a chemical equilibrium between a keto form and an enol. The enol and keto forms are said to be tautomers of each other....
  • aliphatic diazonium coupling
  • carbene
    Carbene

    In chemistry, a carbene is a highly reactive organic molecule containing a carbon atom with six valence electrons and having the general formula: R1R2C: ....
     insertion into C-H bonds


See also

  • Nucleophilic substitution
    Nucleophilic substitution

    In organic chemistry and inorganic chemistry, nucleophilic substitution is a fundamental class of substitution reaction in which an "electron rich" nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom attached to a group or atom called the leaving group; the positive or partially positive atom...