Nucleophiles and electrophiles: Definition

DEFINITION

Key Notes

Nucleophiles

Nucleophiles are electron-rich molecules and react with electrophiles.

Nucleophilic center

The nucleophilic center of a nucleophile is the specific atom or region of the molecule which is electron rich.

Electrophiles

Electrophiles are electron-deficient molecules and can react with nucleophiles.

Electrophilic center

The electrophilic center of an electrophile is the specific atom or region of the molecule which is electron deficient.

Nucleophiles

Most organic reactions involve the reaction between a molecule which is rich in electrons and a molecule which is deficient in electrons. The reaction involves the formation of a new bond where the electrons are provided by the electron-rich molecule.  Electron-rich  molecules  are  called  nucleophiles  (meaning  nucleus- loving). The easiest nucleophiles to identify are negatively charged ions with lone pairs of electrons (e.g. the hydroxide ion), but neutral molecules can also act as nucleophiles if they contain electron-rich functional groups (e.g. an amine).

Nucleophilic center

Nucleophiles have a specific atom or region of the molecule which is electron rich. This is called the nucleophilic center. The nucleophilic center of an ion is the atom bearing a lone pair of electrons and the negative charge. The nucleophilic center of a neutral molecule is usually an atom with a lone pair of electrons (e.g. nitro- gen or oxygen), or a multiple bond (e.g. alkene, alkyne, aromatic ring).

Electrophiles

Electron-deficient molecules are called electrophiles (electron-loving) and react with nucleophiles. Positively charged ions can easily be identified as electrophiles (e.g. a carbocation), but neutral molecules can also act as electrophiles if they contain certain types of functional groups (e.g. carbonyl groups or alkyl halides).

Electrophilic center

Electrophiles have a specific atom or region of the molecule which is electron deficient. This region is called the electrophilic center. In a positively charged ion, the electrophilic center is the atom bearing the positive charge (e.g. the carbon atom of a carbocation). In a neutral molecule, the electrophilic center is an electron- deficient atom within a functional group (e.g. a carbon or hydrogen atom linked to an electronegative atom such as oxygen or nitrogen).