zum Directory-modus

Introduction to Alkenes

Electrophilicity and Nucleophilicity

In chemical reactions of polar molecules, positive and negative charges or partial charges interact with each other. The attractive electrostatic forces among these charges therefore determine such reactions.

Electron-rich atoms or molecules react with electron-deficient atoms or molecules.
Definition "electrophile"
An electron-deficient molecule is called electrophile. It lacks a completed electron shell, i.e. for instance in case of an element of the second period it does not have an electron octet.

Cations like carbenium ions or protons are electrophiles. But neutral molecules can also react as electrophiles. The borone atom of borane (BH3), for example, has only an electron sextett and needs two additional electrons to obtain an electron octet. Radicals are always electrophiles, because they lack at least one electron to get a noble-gas shell.

Reactions of polar molecules
Definition "nucleophile"
A nucleophile is an electron-rich molecule, atom, or ion, which contains at least one free electron pair or a π bond, which is available for reactions with electrophiles.

Anions like the hydroxide ion or the chloride ion are nucleophiles. But uncharged molecules like amines or water can react as nucleophiles as well.

In summary:

Nucleophiles react with electrophiles.

Exercise 1

Exercise 2

Page 3 of 3>