Electrophile and Nucleophile

Electrophiles and nucleophiles play a major role in chemical bonding. They are used in making chemical bonds. The electrophiles accept the electrons, and the nucleophile donates the electrons. The chemical bond is formed between the electrophile and the nucleophile. The electrophiles and nucleophiles are discussed in detail below.

What is an Electrophile?

Electrophiles belong to the category of chemical species involved in the formation of chemical bonds. They are electrophilic; that is, they are deficient in electrons. However, they can accept a pair of electrons to form a chemical bond. Electrophiles are either positively charged or do not have a complete octet. They are always attached to an electron-rich center. The electron-rich center provides the necessary electrons required to complete the bond. Electrophiles are also called Lewis acids because they are electron deficient except for the pair of electrons to form the bond.

Some Examples of Electrophiles

1. Positively charged electrophiles: Atoms and compounds that carry a positive charge are called positively charged electrophiles.

H⁺ , NO⁺ , NO²⁺ , SO₃H⁺

2. Neutral electrophiles: An octet that is incomplete is known as a neutral electrophile.

Lewis acids such as AlCl₃, ZnCl₂, FeCl₃, SnCl₂

All neutral atoms have incomplete octets

Intermediate species like free radicals, carbenes, etc

NOTE: Hydronium ion carries a positive charge, but it is not classified as an electrophile because its octet is complete.

What are Nucleophiles?

Nucleophiles are chemical species that are electron-rich. They are known as Lewis bases because they contain the free electrons ready for donation. The nucleophile donates the pair of electrons to the electrophile and forms the chemical bond. An atom or compound with a lone pair of electrons acts as a nucleophile. The pi bond of the atoms also acts as a source of electron-rich centers.

Some Examples of Nucleophiles

• Negatively charged nucleophile: The nucleophile that carries a negative charge is a negatively charged nucleophile.

• H-, OH-, CN-

• All Lewis bases

• LiAlH₄, RMgX, CH₃CN

Substitution Reaction

The reaction in which a functional group of a compound substitutes another functional group is called Substitution reaction. In other words, a substitution reaction is when a functional group of a compound is removed, and another functional group is replaced at its place. Substitution reactions are widely seen in organic compounds. There are mainly two types of reactions, namely:

• Electrophilic substitution reaction
• Nucleophilic substitution reaction

Electrophilic Substitution Reaction

The reaction that involves the electrophile reaction is known as the electrophilic substitution reaction. In this reaction, an electrophile replaces the functional group of the compound. Electrophilic substitution reactions are further classified into two categories:

• Aliphatic electrophilic substitution reaction: Aliphatic compounds are a straight chain of atoms. In an aliphatic electrophilic substitution reaction, an electrophile approaches the aliphatic chain, replacing the functional atom or group
• Aromatic electrophilic substitution reaction: Aromatic compounds are the ring of compounds which consists of single and double bonds alternately. The aromatic compounds are a source of electron-rich centers. The electrophile attacks on the compound, and thus the product is formed

Nucleophilic Substitution Reaction

The reaction which involves the nucleophile is known as the nucleophilic substitution reaction. In this process, the nucleophile approaches the electron-deficient centre. As a result, the nucleophile replaces the functional group, resulting in a new product.

Addition Reaction

This reaction occurs on the double and triple bonds. The species approaches the double and triple bonds. This species breaks into two parts, one positive and the other negative. The bonds are broken, and the positive and negative positions are formed. The positive intermediate is added to the negative position, and the negative intermediate is added to the positive position. Thus, the new product is formed.

Electrophilic Addition Reaction

These are the most prominent reactions occurring in aromatic compounds. These are a source of electron-rich centers. The electrophiles attack on the pi bond and the formation of new products are formed.

Nucleophilic Addition Reaction

These reactions are very difficult to carry out. The nucleophiles are electron-rich species, and the aromatic compounds are too electron-rich. So, there is repulsion between the two. Therefore, these reactions are carried out in harsh conditions.

Conclusion

By going through this article, we are familiar with the electrophiles and the nucleophile and the types of reactions performed by the electrophile and nucleophile. Electrophiles are electron-deficient species and nucleophiles and electron-rich species. The types of reactions are substitution reaction and addition reaction.