Nucleophiles

A nucleophile is an electron pair donor. It has a lone pair of electrons that it can use to form a new covalent bond with an electron-deficient atom.The name means nucleus loving. Nucleophiles are attracted to positive centres, such as the δ+ carbon atom in the polar carbon-halogen bond of a halogenoalkane.Nucleophiles can be negative ions or neutral molecules. The three nucleophiles you need to know for halogenoalkanes are the hydroxide ion OH^-, the cyanide ion CN^- and the ammonia molecule NH₃.Ammonia has no overall charge but can still act as a nucleophile because the nitrogen atom has a lone pair. Water can also act as a weak nucleophile using a lone pair on its oxygen atom.