Nucleophile

In chemistry, a nucleophile (literally nucleus-lover) is a reagent attracted to nuclei that participates in a chemical reaction by donating electrons in order to bond to a substance. Because nucleophiles donate electrons, they are Lewis bases (see acid-base reaction theories). All molecules or ions with a free pair of electrons can act as nucleophiles, although anions are more potent than neutral reagents.

Nucleophiles take part in nucleophilic substitution, whereby a nucleophile becomes attracted to the nucleus of an element and displaces the group it is bonded to.

In the below example, the oxygen of the hydroxide ion donates an electron to bond with the carbon at the end of the propane molecule. An electron in the carbon-bromine bond is given to the bromine, which is displaced:

Nucleophilic is an adjective that describes the affinity of a nucleophile to the nuclei, while nucleophilicity refers to the nucleophilic character. Nucleophilicity is often used to compare an atom's relative affinity to another's.