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Home > News & Articles > Electrophilic Substitution Reaction: Definitions, Examples, Importance, Types, Mechanism, and Anilines
Updated on 01st July, 2023 , 4 min read
An electrophile (an electron pair acceptor) replaces the functional group attached to a molecule in an electrophilic substitution process. In an electrophilic substitution, the displaced functional group is frequently a hydrogen atom. Electrophilic substitution, also known as electrophilic aromatic substitution reactions, occurs in many compounds containing benzene rings). The electrophilic aliphatic substitution process is a different type of electrophilic substitution reaction. Three stages make up the electrophilic substitution reaction: the synthesis of an electrophile, the creation of a carbocation that serves as an intermediary, and the extraction of a proton from the medium.
A chemical reaction known as an electrophilic substitution reaction occurs when an electrophile replaces the functional group of a molecule. A hydrogen atom usually makes up the displaced functional group. The three steps that electrophilic substitution reactions commonly go through are as follows-
An atom that is connected to an aromatic ring is replaced with an electrophile in electrophilic aromatic substitution processes. Examples of these reactions include Friedel-Crafts reactions, aromatic nitrations, and aromatic sulphonations.
The following are some of the reasons for the importance of substitution reactions-
Electrophilic aromatic substitution reactionsand electrophilic aliphatic substitution reactions are the two main forms of electrophilic substitution reactions that organic compounds experience. The example below demonstrates the electrophilic replacement of a hydrogen atom (from a benzene molecule) with a chlorine atom-
In this instance, the chlorine cation takes the place of a hydrogen atom in the benzene ring by acting as an electrophile. In this electrophilic substitution process, a proton and a chlorobenzene molecule are the end products. The following table gives details about the types of electrophilic substitution reactions-
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Electrophilic Aromatic Substitution Reaction |
Electrophilic Aliphatic Substitution Reaction |
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An atom that is connected to an aromatic ring is replaced with an electrophile in electrophilic aromatic substitution processes. |
It is significant to highlight that in electrophilic aromatic replacements, the aromaticity of the aromatic compound is maintained. |
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Examples of these reactions include Friedel-Crafts reactions, aromatic nitrations, and aromatic sulphonations. |
As a result, using aromatic rings and iodine, bromine, or chlorine, these processes can be employed to produce aryl halides. |
An electrophile replaces the functional group (often hydrogen) in an aliphatic molecule in electrophilic aliphatic substitution processes. The following five categories can be used to group these reactions-
If the electrophilic assault is 180 degrees away from the leaving group (attack from behind), these electrophilic substitution reactions may lead to a configuration inversion.
Three stages make up the electrophilic substitution reaction process-
When an aromatic ring is chlorinated, alkylated, or acylated, an electrophile is produced. Anhydrous aluminum chloride is a particularly helpful Lewis acid in this process. The resultant electrophiles are Cl+, R+, and RC+O, respectively, as illustrated below (when anhydrous aluminum chloride and the attacking reagent are combined).
By attacking the aromatic ring, the electrophile creates an arenium ion or a sigma complex. This arenium ion has an sp3 hybridized carbon. A resonance structure provides stability for this arenium ion. Sigma complexes or arenium ions lose their aromatic properties because electron delocalization ends at the sp3 hybridized carbon.
The [AlCl4]- attacks the sigma complex, which then releases a proton from the sp3 hybridized carbon to reestablish the aromatic property. The following describes the reaction that happens when a proton is taken out of the Sigma complex-
As a result, the hydrogen atom in the benzene ring is changed by the electrophile. Due to the concept's widespread application in other chemical processes, the electrophilic substitution reaction is a crucial one in organic chemistry.
h2> Electrophilic Substitution Reaction of Anilines
A species-seeking electron is an electrophile. Thus, when one electrophile replaces another electrophile in an organic molecule, an electrophilic substitution process takes place. Common electrophilic reactions for anilines include halogenation, nitration, and sulfuration. Aniline has a functional group (-NH2) that donates electrons, making the electrophilic substitution reaction extremely active. Due to its several resonant topologies, the benzene ring has more electrons or negative charges in the ortho- and para-positions than in the meta-position. As a result, in the electrophilic substitution process, anilines are o- and p-directive.
A hydrogen atom is frequently the shifted functional group in an "electrophilic substitution." Numerous benzene-containing abstract compounds go through electrophilic substitution, also known as electrophilic aromatic substitution reactions. The "electrophilic aliphatic substitution reaction" is another type of electrophilic substitution reaction. Three phases make up the electrophilic substitution procedure: making an electrophile, creating a covalent bond that serves as an intermediate, and removing a proton from the medium.
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By - Nikita Parmar 2023-08-25 09:48:44 , 11 min readAns. The functional group of one chemical substance is replaced by another group during the replacement reaction. It is a reaction that occurs when one element or chemical is swapped out for another atom or molecule in a compound.
Ans. When an electrophile assaults a substrate, one or more relatively simple molecules are attached across numerous bonds, resulting in an electrophilic addition process.
Ans. Electrophilic aliphatic substitution and electrophilic aromatic substitution are the two main forms of electrophilic substitution.
Ans. The aryl group exhibits electrophilic substitution more frequently. In compounds that include both an aryl group and a fused benzene ring, electrophiles frequently target the aryl group.
Ans. Lewis acid catalysts, such as AlCl3 or FeCl3, significantly boost the rate of the chlorination of an aromatic ring. This occurs because when the Lewis acids interact with the chlorine molecule, a highly electrophilic Cl+ species is released. Instead, catalysts like AlBr3 or FeBr3 can be utilized to bromide aromatic rings.
Ans. Electrophilic aromatic substitution is one of the most significant procedures in synthetic organic chemistry. Significant intermediates that can be employed as precursors in the production of pharmaceutical, agrochemical, and industrial products are produced by these reactions.
Ans. Chemical substances known as electrophilic reagents acquire or transfer electrons from other molecules or ions during chemical reactions.
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