The Electrophilic Aromatic Substitution name automatically suggests that it is related to chemistry, so before knowing about this topic, let us know about the chemistry first.
What is Chemistry?
Chemistry is the study of the properties and behavior of matter. It’s a scientific study rather than deals more with natural science. The chemistry deals with the element and the compound. Element is made up of one thing, but a compound can have atoms, molecules, and ions on it.
Hence chemistry is divided into 3 branches Physical, Inorganic, and Organic chemistry. The topic which we are going to see is related to Organic chemistry, which is the most difficult part of chemistry. Now we will first explain to you all the 3 terms of the topic Electrophilic Aromatic Substitution.
Organic chemistry
Organic chemistry deals with the carbon compound, which involves studying the properties, compositions, preparation, structure, and reactions. It includes hydrocarbons as well as many compounds. But the structure will contain one carbon for sure.
Electrophilic Aromatic Substitution
Electrophilic Aromatic substitution has its very own importance and its variations.
Electrophilic Means
It can be explained in two ways, but I may suggest if you are not from a science background, then you may have little problem in understanding this term and related words.
As because it requires great attention to understand what core science is, and it is not everyone’s piece of cake, but if you are a science student, then it may be easy for you to understand because you would be already familiar with it.
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Electrophilic Aromatic Substitution
First way
In chemistry, the word electrophile means a molecule or an atom in which a reaction takes place chemically for an atom or a molecule that has an available electron pair ready for bonding.
Note: Electrophilic substance is Lewis acid(that accepts electron pair), but many of them are Bronsted acids(denoted proton).
Second way
The electrophile is a species of chemical that forms a bond with the nucleophile by excepting the electron pairs.
Aromatic Mean
In general organic chemistry, the word aromatic means ring-shaped or rather to be more precise cyclic compound. Sometimes can be a planar structure containing delocalized electron to precise with a pi resonance bond. They provide extra stability to the arrangement or the geometry structure with the same set of atoms.
Substitution means
Very easy to understand the normal meaning of substitute is the same here just a little different is that there is a replacement of functional group, or we can say when one functional group replaces another functional group in a chemical compound, it is called a substitution reaction.
Electrophilic Aromatic Substitution
From which, You can have various reactions taking place, changes undergoing their properties, composition, and structure, and their behavior.
This means that this reaction is organic in which there is an aromatic system in which usually hydrogen atoms are attached, which can be either replaced by the electrophile.
This electrophile can be of various types and important ones like acylation Friedel Crafts reaction, Aromatic nitration, Aromatic sulfonation, Aromatic Halogenation, and alkylation.
The Electrophilic Aromatic Substitution basically involves the replacement of the H atom belonging to a Benzene ring.
The Electrophilic Aromatic Substitution reaction in which Aromaticity of the aromatic system is preserved.
It can be understood by some simple example Bromobenzene is formed from the reaction between Benzene and Bromine the stability of the aromatic ring is not lost.
The main components and their variants like Aryl halide or haloarenes can be prepared via this electrophilic substitution Halogenation reaction.
Substitution Process and mechanism
In the substitution process, the chemical organic process involves replacing hydrogen with an electrophile, and the mechanism is a little complex to understand and acquire good knowledge to understand it.
Mechanism
In the Arene Nucleophile, the new sigma bonds are formed from a carbon-carbon double bond during the process.
During this process, by breaking down the carbon-hydrogen sigma bonds, protons are removed.
To restore the aromaticity, the carbon-carbon double bond is reformed.
To understand it furthermore well, we will understand it in 2 more steps.
The pi electrons are attacked by electrophile.
The pi electrons are attacked by the electrophile in the benzene ring during the electrophilic aromatic substitution. As a result arenium ion is formed, which is a stabilized resonance carbocation.i
The electrophile firmed during the is a very slow process takes a long time the 3 main contributor resonance have basically formed the ion.
As there is the activation of high energy and due to some other factors, it can lead to the loss of aromaticity.
The Deprotonatiin of Arenium ion
From the weak base, the arenium ion is deprotonated. The intermediate carbocation is formed, which attacks from a weak base that results in the protons loss.
From the pi bond, protons are used to restore the aromaticity. This is an exergonic and fast process. The loss of a proton from a carbocation Results in electrophile attacking the benzene ring.
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