Nucleophiles: Definition and Recognition
What is a Nucleophile?
Definition
Nucleophile
A nucleophile is an electron-rich species that donates a pair of electrons to form a covalent bond. The term “nucleophile” originates from the Greek words nucleus (meaning core) and philos (meaning loving), indicating its affinity for positively charged or electron-deficient centers.
Key Features of Nucleophiles:
- Electron-rich nature: Nucleophiles possess a high electron density, often due to lone pairs of electrons or a negative charge.
- Ability to donate electrons: They have lone pairs or $\pi$-electrons available for bonding.
- Attraction to electrophiles: Nucleophiles are drawn to electron-deficient species, such as positively charged ions or atoms with partial positive charges
- Negatively charged species: Hydroxide ion $OH^-$, cyanide ion $CN^-$, halide ions $Cl^-$, $Br^-$, $I^-$, and hydrosulfide ion $HS^-$.
- Neutral molecules: Ammonia $NH_3$, water $H_2O$, and methylamine $CH_3NH_2$.
- The hydroxide ion $OH^-$ is a classic nucleophile.
- It has three lone pairs of electrons on the oxygen atom, making it highly electron-rich and ready to donate an electron pair to an electrophile.
How to Recognize a Nucleophile?
- Identifying nucleophiles in a reaction requires paying attention to species with either a negative charge or lone pairs of electrons.
- These features make a species electron-rich and capable of donating electrons.
