Definition of Lewis acid in US English:

Lewis acid


  • A compound or ionic species which can accept an electron pair from a donor compound.

    • ‘In a coordinate covalent bond, both electrons are donated by the Logan, a Lewis base, to the metal atom, a Lewis acid.’
    • ‘Like the Brönsted superacids, Lewis superacids are simply very strong Lewis acids.’
    • ‘In this electrophilic aromatic substitution, the first electrophile is the Lewis acid that accepts the halogen from an alkyl halide (the nucleophile).’
    • ‘A Lewis acid, such as aluminum chloride, is often the catalyst used for this reaction.’
    • ‘In simple additions, the carbonyl compounds can behave as both Lewis acids and Lewis bases depending on what reagents are present.’


1940s: named after Gilbert N. Lewis (1875–1946), American chemist.