Reactivity 3.4 – Electron-pair sharing reactions

R3.4.6 & R3.4.7 – Lewis acids and bases (HL)

📌 Defining acids and bases

  • A Lewis acid is defined as a species that can accept a lone pair of electrons
  • A Lewis base is defined as a species that can donate a lone pair of electrons
  • Unlike the Brønsted-Lowry theory covered earlier, this theory focuses on lone pairs of electrons
  • By these definitions we can understand that Lewis acids are electrophiles while lewis bases are nucleophiles

Examples

  1. Lewis acids : BF3(incomplete octet is useful for accepting lone pairs), H2O
  2. Lewis bases : NH3, H2O /

Note : Water is considered to be both a Lewis acid and a Lewis base. This is known as an amphoteric species