Main Difference – Electrophile vs Nucleophile
The chemical reactions between organic and inorganic chemical species mostly occur through electrophiles and nucleophiles. Electrophiles and nucleophiles can be defined as derivatives of atoms or molecules. The main difference between electrophile and nucleophile is that electrophiles are atoms or molecules that can accept electron pairs whereas nucleophiles are atoms or molecules that can donate electron pairs.
Key Areas Covered
1. What is Electrophile
– Definition, Characteristics, Examples
2. What is Nucleophile
– Definition, Characteristics, Examples
3. What is the difference between Electrophile and Nucleophile
– Comparison of Key Differences
Key Terms: Electrophile, Electrophilicity, Electrophilic Addition Reaction, Electrophilic Substitution Reaction, Nucleophile, Nucleophilicity, Nucleophilic Addition Reaction, Nucleophilic Substitution Reaction, Lewis Acid, Lewis Base
What is an Electrophile
An electrophile is an atom or molecule that can accept an electron pair from an electron rich species and form a covalent bond. Electrophiles are positively or neutral charged atoms or molecules having free orbitals for incoming electrons.
Electrophiles are called Lewis acids due to their ability to accept electrons. An electrophile is created when an atom or a molecule lacks electrons to obey the octet rule or have a positive charge that needed to be neutralized in order to become stable.
For example, Hydronium ion (H3O+) is an electrophile. It has a positive charge and the hydrogen atom has free space for incoming electrons. Therefore, it can accept electron pairs from a Lewis base such as –OH to form H2O molecule.
In organic chemistry, electrophiles undergo addition and substitution reaction. For example, the addition of halogens to alkenes occurs via electrophilic addition reactions.
Figure 01: Alkene and Bromine Addition
Electrophilic substitution reactions include the substitution of an electrophile, replacing a functional group of a molecule. Most commonly, electrophilic substitution reactions can be observed with benzene.
Figure 02: Electrophilic substitution of an electrophile to benzene, replacing a hydrogen atom.
The strength of an electrophile is determined by its electrophilicity. Electrophilicity is a term used to indicate the electrophilic nature of an electrophile. This electrophilicity depends on factors such as charge of the electrophile.
What is Nucleophile
A nucleophile is an atom or molecule which can donate electron pairs, and due to their ability, it is also called Lewis base. Nucleophiles can donate electrons to electrophiles. Molecules having pi bonds or atoms or molecules having free electron pairs act as nucleophiles.
Nucleophiles are normally negatively charged. Even neutrally charged molecules with electron rich atoms can behave as nucleophiles. Nucleophiles also show specific reactions such as Nucleophilic addition and Nucleophilic substitution reaction.
Figure 03: Reaction between a nucleophile and electrophile
The above example shows the reaction between a nucleophile and electrophile. Here, H2O molecule acts as the nucleophile. It donates electrons to the carbocation which has a positive charge.
Figure 04: Nucleophilic Substitution
The above image shows a Nucleophilic substitution reaction. The nucleophile is shown as “Nu” and the functional group “X” in the benzene ring is replaced by the nucleophile. Then, the nucleophile is attached to the benne ring while “X” group leaves the benzene ring. Therefore, “X” is called the leaving group.
Nucleophilicity is an important term regarding nucleophiles. Nucleophilicity determines the strength of a particular nucleophile. This nucleophilicity depends on many factors such as charge, basicity, polarizability, etc. For example, when the negative charge of the nucleophile is increased, the nucleophilicity is increased. That means nucleophiles bearing a high negative charge act as excellent nucleophiles.
Difference Between Electrophile and Nucleophile
Definition
Electrophile: An electrophile is an atom or molecule that can accept an electron pair from an electron rich species and form a covalent bond.
Nucleophile: A nucleophile is an atom or molecule which can donate electron pairs.
Electrical Charge
Electrophile: Electrophiles are either positively charged or neutrally charged.
Nucleophile: Nucleophiles are either negatively charged or neutrally charged.
Chemical Reactions
Electrophile: Electrophiles undergo electrophilic addition and electrophilic substitution reactions.
Nucleophile: Nucleophiles undergo nucleophilic addition and nucleophilic substitution reactions.
Other Names
Electrophile: Electrophiles are also called Lewis acids.
Nucleophile: Nucleophiles are also called Lewis bases.
Conclusion
Electrophiles and nucleophiles play a major role in chemical reactions regarding organic chemistry and inorganic chemistry. The main difference between electrophile and nucleophile is that electrophiles are atoms or molecules that can accept electron pairs whereas nucleophiles are atoms or molecules that can donate electron pairs.
References:
1. “Nucleophile.” Chemistry LibreTexts. Libretexts, 21 July 2016. Web. 27 June 2017.
2. “Nucleophiles and Electrophiles .” Nucleophiles and Electrophiles. N.p., n.d. Web. Available here. 27 June 2017.
Image Courtesy:
1. “Alkene-bromine-addition-2D-skeletal” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia
2. “Electrophilic-aromatic-substitution-general” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia
3. “NS1 reaction part2 recombination carbocation nucleophile” By V8rik at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
4. “Mechanism nucleophilic aromatic substitution” By Sponk (talk) – Own work (Public Domain) via Commons Wikimedia
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