Lewis acid is a chemical species that reacts with a Lewis
base to form a Lewis
adduct. A
Lewis base, then, is any species that donates a
pair of electrons to a Lewis acid to form a Lewis adduct. For example, OH
- and NH
3 are Lewis bases, because they can donate a lone pair of electrons. In the adduct, the Lewis acid and base share an electron pair furnished by the Lewis base. Usually the terms Lewis acid and Lewis base are defined within the context of a specific
chemical reaction. For example, in the reaction of
Me3B and
NH3 to give Me
3BNH
3, Me
3B acts as a Lewis acid, and NH
3 acts as a Lewis base. Me
3BNH
3 is the Lewis adduct. The terminology refers to the contributions of
Gilbert N. Lewis.