Friedel craft alkylation reaction

Friedel craft alkylation reaction

In this Friedel craft alkylation reaction Arenes, an alkyl group is introduced on the benzene or arene ring by using the alkyl halide in presence of anhydrous AlCl₃. The reagents can be represented as

1. _{Anhydrous AlCl3}
2. Anhydrous FeCl₃
3. BF₃
4. TiCl₃
5. ZnCl₂
6. SnCl₄

The mechanism of the reaction starts with the formation of an Alkyl carbonium ion. Alkyl halide reacts with anhydrous AlCl3 and acts as a halogen carrier to produce an alkyl carbonium ion (electrophile). The stability of an alkyl carbonium ion is important. 

The alkyl carbonium ion formed reacts with an aromatic ring to produce resonating forms of the arene. This positive charge on the aromatic ring a stabilized by resonating forms.
In resonance hybrid structure the positive charges are distributed over five carbon atoms so relative positive charge density on each carbon atom is very less and thus it is stabilized.

The structure three formed in the resonating forms further stabilizes to give a mono-substituted alkyl derivative.

The H+ ion release in this reaction joins with the conjugate base to form a byproduct here it is termed as spent acid.

The monosubstituted derivative of arenes uses an alkyl halide to give the monosubstituted derivative. While deciding the product of alkylation stability of the carbonium ion formed is to be taken into account. As shown in the examples 

 

 

 

 

Check out reactions

Chlorination Reaction	Bromination Reaction	Nitration Reaction
Sulphonation Reaction	Friedel Craft Alkylation Reaction	Friedel craft Acylation Reaction

 

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Friedel craft alkylation reaction

Friedel craft alkylation reaction

In this Friedel craft alkylation reaction Arenes, an alkyl group is introduced on the benzene or arene ring by using the alkyl halide in presence of anhydrous AlCl₃. The reagents can be represented as

1. _{Anhydrous AlCl3}
2. Anhydrous FeCl₃
3. BF₃
4. TiCl₃
5. ZnCl₂
6. SnCl₄

The mechanism of the reaction starts with the formation of an Alkyl carbonium ion. Alkyl halide reacts with anhydrous AlCl3 and acts as a halogen carrier to produce an alkyl carbonium ion (electrophile). The stability of an alkyl carbonium ion is important. 

The alkyl carbonium ion formed reacts with an aromatic ring to produce resonating forms of the arene. This positive charge on the aromatic ring a stabilized by resonating forms.
In resonance hybrid structure the positive charges are distributed over five carbon atoms so relative positive charge density on each carbon atom is very less and thus it is stabilized.

The structure three formed in the resonating forms further stabilizes to give a mono-substituted alkyl derivative.

The H+ ion release in this reaction joins with the conjugate base to form a byproduct here it is termed as spent acid.

The monosubstituted derivative of arenes uses an alkyl halide to give the monosubstituted derivative. While deciding the product of alkylation stability of the carbonium ion formed is to be taken into account. As shown in the examples 

 

 

 

 

Check out reactions

Chlorination Reaction	Bromination Reaction	Nitration Reaction
Sulphonation Reaction	Friedel Craft Alkylation Reaction	Friedel craft Acylation Reaction

 

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Reaction Intermediate

Reaction IntermediateReaction Intermediate:   In,  organic ... https://www.myetutors.com/?p=15706&feed_id=66 #cbse #jee2022 #neet2022 #chemistry #exam

Bond Fission

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Homolytic and Heterolytic fission

Homolytic and Heterolytic fission:

Bond fission is the process of breaking covalent bonds present in organic molecules. It occurs in the following two ways

Homolytic fission:

Bond fission occurs symmetrically, and shared electrons between two elements are equally distributed between them to form atoms or free radicals.

Heterolytic fission: 

Bond fission occurs unsymmetrically, and shared electrons between two elements are not equally distributed between them. This fission results in the formation of 

1.  Electrophiles
2. Nucleophiles

Electrophiles:

Electrophiles are electron-deficient species that have a tendency to take up electrons, and therefore, they act as Lewis acids.

These are of the following types:

Positively Charged Electrophiles :

H⁺, X⁺ , R⁺, NO₂⁺, NO⁺, SO₃H⁺.

Neutral electrophiles:

These are of the following types:

Neutral electrophiles with an incomplete octet state have a central atom that is electron deficient, that is, it does not have an octet state.
For example, BeX₂, ZnCl₂, BH₃, BX₃, AlX₃, FeX₂

Neutral electrophiles with an extended octet state have a central atom with a vacant d-orbital, which can extend its octet state. For example, SnCl₄, PCl5, IF₇

Nucleophiles:

Nucleophiles are species that have lone pairs of electrons, available for donation, and therefore, they act as Lewis bases.

These are of the following types:

Negatively charged:

H^–, OH^–, R ^–, O^–, CH₃⁻, X^–, SH^–, R^–, S^–.

Neutral:

The central atom with lone pair of electrons to donate. For example,
NH₃  (RNH₂,  etc.)
O (H₂O, HOR, R – O – R)
S (R–SH, R– S– R, H₂S)

Ambidentate nucleophiles

They have two nucleophilic centers, one of which is negatively charged and the other one is neutral.
For example, C≡N, O−N=O, NO₂

 

 

 

 

 

 

 

 

 

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Sulphonation reaction Arenes

Sulphonation reaction Arenes:

 

in this Sulphonation reaction Arenes, a sulphonic acid group is introduced on the benzene or arene ring by using the concentrated sulphuric acid or oleum. The reagents can be represented as

1. Concentrated H₂SO₄ 
2. Concentrated H₂SO₄ + SO₃
3. Oleum

There is equilibrium between concentrated sulphuric acid and Sulphur trioxide.

the mechanism of the reaction starts with the formation of Sulphur trioxide gas. Protonation of Sulphur trioxide occurs by forming sulphonium ion, this is due to the fact that there is two dπ-dπ bonds in Sulphur trioxide. These bonds are weak bonds and readily react with a proton to form a sulphonium ion (an electrophile). 

the sulphonium ion formed reacts with an aromatic ring to produce resonating forms of the arene. This positive charge on the aromatic ring a stabilized by resonating forms.
In resonance hybrid structure the positive charges are distributed over five carbon atoms so relative positive charge density on each carbon atom is very less and thus it is stabilized.

The structure three formed in the resonating forms further stabilizes to give mono substituted Sulpho derivative.

The H+ ion release in this reaction joins with the conjugate base to form a byproduct here it is termed as spent acid.

H⁺  + HSO₄ ^-1 → H₂SO₄
The monosubstituted derivative of arenes uses a Fuming sulphuric acid always uses a higher concentration of SO₃ as it is a hygroscopic material and it absorbs water formed in the first step as a result of which more forward reaction takes place and concentration often Sulphonium ion increases the reaction mixture thus the rate of reaction increases and formation of product is higher yield.

 

 

Check out reactions

Chlorination Reaction	Bromination Reaction	Nitration Reaction
Sulphonation Reaction	Friedel Craft Alkylation Reaction	Friedel craft Acylation Reaction

 

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Reaction Intermediate

Reaction Intermediate:

In,  organic chemistry there are four types of reaction intermediates that are formed during the reaction. These are formed due to bond fission. There can be Homolytic or heterolytic fission to form intermediates as discussed below

Carbon-free radical:

This is formed by homolytic fission on the bond. The homolytic fission of bond forms four types of the classical intermediate they are methyl carbon free radical, primary carbon-free radical, secondary carbon free radical, and tertiary carbon free radical. They are as shown below

Criteria of stability:

Stability of Carbon-free radical  ∝  Resonance

                                                          ∝ Electron releasing groups

Order of Stability:

Carbonium ion or Carbocation:

This is formed by a heterolytic fission bond. The heterolytic fission of bond forms four types of the classical intermediate they are methyl carbocation, primary carbocation, secondary carbocation, and tertiary carbocation. The other type of carbonation is nonclassical carbocation. They are as shown below

Criteria of stability:

Stability of Carbocation  ∝  Resonance

                                              ∝  Electron releasing groups

Order of Stability:

Carbanion ion:

This is formed by heterolytic fission on the carbon-carbon bond. The heterolytic fission of bond forms four types of the classical intermediate they are methyl carbanion, primary carbanion, secondary carbanion, and tertiary carbanion. The other type of carbanion is nonclassical carbocation. They are as shown below

 

Criteria of stability:

Stability of carbanion  ∝  Resonance

                                        ∝  Electron releasing groups

Order of Stability:

 

Carbene:

This is formed by heterolytic or hemolytic fission on the bond. The heterolytic fission of bond forms two types of the intermediate they are singlet carbene and triplet carbene.  They are as shown below

 

Criteria of stability:

Stability of carbanion  ∝  Resonance

                                        ∝  Electron releasing groups

Order of Stability:

 

 

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Reaction Mechanism 04 | Chlorination of benzene | SE Reaction

Isomerism 12 | Conformational Isomerism 03 | Cycloalkanes

Reaction Mechanism 02 |Electrophilic substitution 01

Isomerism 11 | Conformational Isomerism 02 | Butane

Isomerism 10 | Conformational Isomerism 01 | alkanes

Isomerism 09 | Stereospecific addition reaction of alkanes

Isomerism 08 | optical 03 | How to find R & S configuration

Isomerism 08 | optical 02 | How to calculate total optical isomers

Chemical Kinetics 04 : Rate law Using initial rate method

Chemical Kinetics 02: rate constant Introduction and application

Isomerism 09 | optical 01 | Enantiomer | diastereomers |JEE | NEET

Isomerism 06 Geometrical Syn-Anti isomerism JEE | NEET