Q.In the reaction CH3Br + OH(-) -> CH3OH + Br(-), identify the electrophile and the nucleophile and explain your choice.

The Electrophile–Nucleophile Concept: A First Look

Imagine you are in a crowded room. Some people are constantly reaching out to shake hands — they want to connect, to grab something. Others are holding their hands close, waiting for someone to come to them. In organic chemistry, molecules behave the same way.

The Intuition

Every chemical reaction is about electron movement. Some species are electron-poor — they want to accept electrons to become stable. Others are electron-rich — they have extra electrons and are happy to donate them.

• Electrophile (from Greek philos = loving, electron = electron): "Electron-loving" — a species that loves electrons and seeks them out. It is electron-deficient (positive charge, partial positive charge, or an empty orbital).
• Nucleophile (from Greek nucleus = nucleus, philos = loving): "Nucleus-loving" — a species that loves positive nuclei because it has excess electrons to donate. It is electron-rich (negative charge, lone pairs, or pi bonds).

The Precise Statement

Electrophile: Any atom, ion, or molecule that accepts a pair of electrons to form a new covalent bond. It is Lewis acid (electron-pair acceptor).

Nucleophile: Any atom, ion, or molecule that donates a pair of electrons to form a new covalent bond. It is Lewis base (electron-pair donor).

How to Identify Them

The Arrow-Pushing Convention

In organic chemistry, we show electron movement with curved arrows:

• Arrow starts at the nucleophile (where electrons come from) — usually a lone pair or a pi bond.
• Arrow ends at the electrophile (where electrons go) — usually at a positive charge or an empty orbital.

Example: Reaction of hydroxide ion with methyl bromide

The arrow goes from the lone pair on $\ce{O}$ (nucleophile) to the carbon atom in $\ce{CH3Br}$ (electrophile, because $\ce{Br}$ pulls electron density away, making carbon partially positive). …