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Electrophile is an atom, molecule, or ion that is deficient in electrons. Electrophile seeks out another atom or molecule that has an electron pair accessible for bonding in a chemical reaction. Electrophiles either contain a positive charge or a neutral charge where the empty electron orbital is attracted to an orbital centre that is rich in electrons. Electrophiles have the ability to accept pairs of electrons. The reagent that attacks the negative of the molecule or loves electrons is referred to as an electrophile. In simpler terms, electrophiles are electron-deficient molecules with empty orbitals.
Key Terms: Electrophile, Electrons, Atom, Nucleophile, Positive Charge, Electrophilic Substitution, Addition Reaction, Lewis Acids
What is Electrophile?
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Electrophiles are any molecules, ions or atoms that accept an electron pair and form bonds with nucleophiles. The term ‘electrophile’ is made from “electro” derived from electrons and “phile” which means loving. It means that electrophiles are electron-loving chemical species. Electrophiles are generally positively charged or neutral species. They are electron-deficient molecules with empty orbitals.
Example: H+ is an electrophile and It could accept a pair of electrons from the Lewis base OH- to form H2O.
- Electrophiles are electron-deficient and are attracted towards electrons.
- Electrophiles are also called Lewis acids because they accept electrons.
- They are involved in electrophilic substitution and addition reactions.
- They are either positively or neutrally charged molecules.
- Electrophiles attack electron-rich areas such as carbon-carbon double bonds.
- The movement of electrons is affected by the density and the movement is from a high-density area to a low-density area.
- Electrophiles favour electrophilic addition and electrophilic substitution reactions.
Electrophile
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Types of Electrophile
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Electrophiles can be classified into various types as follows:
Positively Charged Electrophiles
Electrophiles that carry a positive charge are called positively charged electrophiles. Some positively charged electrophiles are:
- H+
- SO3H+
- NO+
- NO2+
- X+
- R+
- C6H5N2+
Neutral Electrophiles
Neutral electrophiles showcase electron deficiency. Examples of neutral electrophiles are as follows:
- All Lewis Acids: BF3, AlCl3, SO3, ZnCl2, BeCl2, FeCl3, SnCl2, CO2, SnCl4.
- The neutral atom that accepts electrons from the substrates: *C = O, R *COCl, R – * Mg – X, *I – Cl, CH3 – *CN, R*–Cl, R*–O,
Also Read: Classification of Organic Compounds
Addition of Halogens
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Halogen addition is a simple organic reaction where a halogen molecule is added to a carbon-carbon double bond of an alkene functional group. In halogen addition reactions, the reaction occurs between alkenes and electrophiles, most commonly halogens.
One common reaction is the use of bromine water to titrate against a sample to determine the number of double bonds present.
| C2H4+ Br2 → BrCH2CH2Br |
- The electrophilic Br-Br molecule forms a -complex with the alkene molecule which is rich in electrons.
- Here, Bromine acts as an electrophile and the alkene acts as an electron donor.
- The three-membered bromonium ion 2 with two carbon atoms and a bromine atom emerges with the release of Bromium.
- The attack of Br from the backside opens the bromonium ion.
- The vicinal dibromide has an antiperiplanar configuration as a result of the above reaction.
- In case other nucleophiles like water or alcohol are present, they can attack 2 and create either alcohol or ether.
Addition of Hydrogen Halides
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Hydrogen halides are simple polar molecules that add across the double bond of an alkene.
- In hydrohalogenation, hydrogen halides like hydrogen chloride (HCl) are added to alkenes to create alkyl halides.
- The reaction of HCl with ethylene produces chloroethane.
- In comparison to the halogen addition, the reaction proceeds through a cation intermediate.
Electrophiles
Chiral Derivatives
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A lot of electrophiles can be found visually steady and chiral.
- Chiral electrophiles have the typical characteristic feature of being optically pure.
- In Shi epoxidation, a fructose-derivative organocatalyst reagent is used.
- The trans-disubstituted and trisubstituted are exposited by the catalyst with high enantioselectivity.
- Until the catalytic cycle has continued the ketone i.e., Shi catalyst is oxidized to the active dioxirane form of stoichiometric oxide.
What is Nucleophile?
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Nucleophiles are electron-rich chemical species that donate electron pairs to electron-deficient molecules.
- Carbanions, water, ammonia, and the cyanide ion are a few examples of nucleophiles.
- They must be electron-rich chemical entities with at least one lone pair of electrons since the nucleus of an atom is positively charged.
- Since both negatively charged and neutral nucleophiles have at least one unshared pair of electrons, they have a higher tendency to donate these electrons to electron-deficient species, and hence act as Lewis bases.
- Nucleophiles target the substrate molecule where the electron density is lowest.
Nucleophile Examples
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Difference between Electrophile and Nucleophile
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The main differences between electrophiles and nucleophiles are as follows:
| Electrophile | Nucleophile |
|---|---|
| Electrophile acquires an electron pair with an empty orbital. | Nucleophiles have a loosely held electron pair that can be readily supplied. |
| Electrophile accepts electron pair | Nucleophile supplies electron pair |
| Electrophile creates an additional bond with the nucleophile. | The covalency of a nucleophile increases by one unit. |
| They are Lewis acids that can accept a pair of electrons. | They are Lewis bases that can donate a pair of electrons. |
| Example: All positively charged species like H+, NO2+, and electron-deficient species like BF3, AlCl3 | Example: All negatively charged species such as OH–, CN–, and electron-rich species such as H2O, NH3 |
Things to Remember
- Electrophiles are molecules, ions or atoms that are deficient in electrons.
- Electrophiles are engaged in electrophilic substitution and electrophilic addition reactions.
- They are also called Lewis acids as they accept electrons.
- There can be either a positive or negative charge on electrophiles.
- Electrons attack atoms with a lot of electrons, such as carbon-carbon double bonds, which have a lot of electrons.
- Nucleophiles are electron-rich molecules that donate electron pairs to electrophiles and form chemical bonds.
Previous Years’ Questions
- Pick out the electrophiles from the following species… [AMUEEE 2013]
- Electrophilic reagents are…
- Electrophilic addition reaction is easily given by… [UP CPMT 2010]
- The effective electrophile in aromatic sulphonation is… [MU OET 2010]
- +I effect is shown by…
- In Kjeldahl's method for estimation of nitrogen present…
- Which of the following species is not electrophilic in nature…
- Which of the following can behave as both electrophile and nucleophile…
- Order of reactivity towards nucleophilic substitution reaction… [AMUEEE 2009]
- Which one is most reactive towards nucleophilic addition reaction…
Sample Questions
Ques. What is the difference between a nucleophile and an electrophile? (5 Marks)
Ans. The differences between a nucleophile and an electrophile are as follows:
| Nucleophile | Electrophile |
|---|---|
| An atom or molecule that may donate electron pairs is known as a nucleophile. | An electrophile is a molecule or atom that can receive an electron pair from an electron-rich species and establish a covalent connection with it. |
| Nucleophiles are charged either negatively or neutrally. | Electrophiles are classified as either positively or neutrally charged. |
| Nucleophilic addition and substitution reactions occur in nucleophiles. | Electrophilic addition and substitution reactions occur in electrophiles. |
| Electrophiles are also referred to as Lewis acids. | Nucleophiles are also referred to as Lewis bases. |
Ques. What Is an Electrophile and How to Identify it? (2 Marks)
Ans. Electrophiles acquire an electron pair in order to establish a covalent bond, while nucleophiles contribute an electron pair in order to form a covalent bond. Both the chloride and iodide ions are nucleophiles, meaning they have a charge and are prepared to donate an electron. They have empty electron orbitals that are pulled to an electron-rich centre and either has a positive charge or are neutral, whereas nucleophiles have a pair of electrons to contribute.
Ques. Can electrophiles be neutral? (3 Marks)
Ans. Electrophiles are neutral or positively charged entities that can establish bonds with nucleophiles by accepting a pair of electrons. An electrophile is referred to as a negatively charged species that helps in the formation of a connection with a nucleophile by accepting a pair of electrons. An electrophile is a negatively charged species that can form a connection with another electrophile by accepting a pair of electrons. Electrophiles are normally neutral species that can form a connection with a nucleophile by accepting a pair of electrons.
Ques. What are electrophiles? Give some examples. (2 Marks)
Ans. Electrophiles are species that are electron-deficient yet can accept electron pairs from electron-rich species. Carbonyl compounds and carbocations are two examples. An electron-rich species that contribute electron pairs to electron-deficient species is known as a nucleophile.
Hydronium ion (H3O+, from Bronsted acids), boron trifluoride (BF3), aluminium chloride (AlCl3), and the halogen molecules fluorine (F3), chlorine (Cl2), bromine (Br2), and iodine (I2) are examples of electrophiles.
Ques. What are strong electrophiles? (3 Marks)
Ans. Electrophilicity, or the ability to attract electrons, determines the strength of an electrophile. As a result, a positively charged entity that needs electrons to stay stable is a good and powerful electrophile. A carbonyl (C=O), for example, can add a positive charge to the carbon through resonance. A strong electrophile must have an electrophilic centre or atom. The electrophilic atom must also be able to accept a new sigma bond.
Ques. What role do Electrophiles play in chemical reactions? (3 Marks)
Ans. Electrophiles are electron-deficient atoms or molecules that have a partial (or full) positive charge and will seek an electron pair to establish a covalent connection. Electrophiles are molecules having a positive charge with a deficiency in electrons, allowing them to react by sharing electron pairs with electron-rich nucleophiles. In these reactions, double-bond molecules are frequently present. A positively charged carbon atom is connected to three additional atoms to form a carbocation.
Ques. What is the purpose of electrophilic addition? (2 Marks)
Ans. Electrophilic addition reactions are a type of reaction that allows C=C and C=C to be converted into a variety of functional groups such as alkyl halides and alcohols. The addition is the inverse of elimination in terms of concept, and it can be used to make alkenes.
An electrophile and a nucleophile combine to add double or triple bonds in an electrophilic addition process. An electrophile is a molecule that has a proclivity for reacting with other molecules that have a pair of electrons that can be donated.
Ques. What does electrophilic addition produce? (2 Marks)
Ans. In organic chemistry, an electrophilic addition reaction occurs when a double or triple bond in a chemical molecule is broken, resulting in the production of two new bonds. The creation of an electrophile X+ that forms a covalent connection with an electron-rich, unsaturated C=C bond is the driving force behind this reaction. During the creation of the C-X bond, the positive charge on X is transferred to the carbon-carbon bond, generating a carbocation.
Ques. What are polar functional groups? (3 Marks)
Ans. A functional group refers to the category of atoms or bonds which are present inside a substance and are responsible for the compound's unique chemical reactions in organic chemistry. In spite of the chemical in which it is found, similar functional groups tend to behave similarly and undergo the same reactions. In the case of organic compound naming, the functional groups are important; combining the functional group names with the names of the parent alkanes helps to differentiate the compounds.
- For example, oxygen takes electrons from the C-atom and creates a partial charge:Cδ + = Oδ-
- C is an electrophile because it is electron-deficient, whereas O is a nucleophile because it is electron-rich.
- Electrophiles and nucleophiles are polar functions.
Ques. What is an electrophilic substitution reaction? (2 Marks)
Ans. An electrophilic substitution reaction is defined as a reaction in which a chemical group is displaced by an electrophile. Friedel Craft’s acylation and alkylation are popular examples of electrophilic substitution reactions.
Ques. What is nucleophilic substitution reaction? (2 Marks)
Ans. Nucleophilic substitution reaction refers to a reaction in which a nucleophile attacks an electron-deficient centre or an electrophile and displaces it. For instance, alkyl bromide hydrolysis is an example of a nucleophilic substitution reaction.
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