Question

What are electrophiles and nucleophiles? Explain with examples.

Answer 1

Electrophiles and Examples of Electrophiles:

• “A reagent that takes away an electron pair is called electrophile (E⁺).”
• The carbon atom in carbocations has a sextet configuration; hence, it is electron-deficient and can accept a pair of electrons from the nucleophiles.
• Carbocations$\left(\stackrel{+}{\text{C}}{\text{H}}_3\right)$ and neutral molecules having a functional group such as the carbonyl group acts as an electrophile.

Types of electrophiles:

1. Neutral molecules with vacant orbitals of the central atom- E.g.,${\mathrm{BF}}_3,{\mathrm{AlCl}}_3$ etc.
2. Molecules with positive charges or free radicals on the central atom. E.g., ${{\mathrm{NO}}_2}^{+},{{\mathrm{CH}}_3}^{+},{\mathrm{CH}}_3-{\mathrm{C}}^{+}=\mathrm{O}$ etc.
3. Molecules with central atoms are surrounded by more electronegative atoms. E.g., ${\mathrm{CO}}_2,{\mathrm{SO}}_3$etc.

Nucleophiles and Examples of nucleophiles:

• ''A reagent that brings an electron pair is called a nucleophile."
• The movement of an electron pair from the nucleophile to the electrophile is represented by a curved-arrow notation.
• An example of a nucleophile is negatively charged species such as cyanide$\left({\mathrm{NC}}^{-}\right)$ ion.
• Neutral species such as water is$\left({\mathrm{H}}_2\mathrm{O}\right)$is also an example of nucleophiles due to the presence of lone pairs of electrons.