# Nucleophiles, electrophiles and curved arrows

A nucleophile is electron-rich and donates a pair of electrons. An electrophile is electron-poor and accepts a pair. A curved arrow shows a pair of electrons moving, from the nucleophile toward the electrophile.

Chemistry (university) · Part 10: Organic reactions and mechanisms · Card 1 of 10 · Last updated 2026-10-19

## Analogy

A nucleophile is a hand reaching out to give. An electrophile is a hand held out to take.

## Example

**Hydroxide + chloromethane**

HO⁻ (nucleophile, lone pair)
attacks C in CH₃–Cl (electrophile, δ+)
Arrow 1: lone pair to carbon
Arrow 2: C–Cl bond to chlorine

## In practice

Nearly every organic mechanism is a story of curved arrows: where electrons start and where they end up.

## Practice

### Flashcards

- **What is a nucleophile?** An electron-rich species that donates a pair of electrons to form a bond.
- **Where does a curved arrow start?** At the electrons: a lone pair or a bond.

## Questions people ask

### How can I tell which species is the nucleophile?

Look for lone pairs, negative charges or pi bonds, because these are electron-rich. Hydroxide, ammonia and water are nucleophiles. The electrophile is usually a carbon bonded to a more electronegative atom, which makes it partly positive, or a positive ion such as a carbocation.

### Where should a curved arrow start and end?

The arrow starts where the electrons are, at a lone pair or a bond, and points to where they go, an atom or a new bond. It never starts at an atom without electrons. A full-headed arrow shows two electrons moving, and a half-headed arrow shows one.

## Related concepts

- [Carbocation stability](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-10/chemistry-university-part-10-concept-4)
- [Reaction mechanism](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-6/chemistry-university-part-6-concept-8)

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