How do you predict lewis acid / base reactions?
1 Answer
You identify the Lewis acid and the Lewis base and join them to form an adduct with a coordinate covalent bond.
LEWIS ACIDS
A Lewis acid will have a vacant orbital. Various species can act as Lewis acids.
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All cations (e.g., Cu²⁺, Fe²⁺, Fe³⁺)
Cu²⁺ + 4NH₃ → Cu(NH₃)₄²⁺ -
An atom, ion, or molecule with an incomplete octet of electrons (e.g., BF₃, AlF₃).
BH₃ + NH₃ → H₃B⁻-N⁺H₃ -
Molecules in which the central atom can expand its octet (e.g., SiBr₄, SiF₄).
SiF₄ + 2F⁻ → SiF₆²⁻ -
Molecules with double or triple bonds between two atoms of different electronegativities. Examples are CO₂ and SO₂.
O=C=O + OH⁻ → HO-C(=O)O⁻ -
Brønsted-Lowry acids (e.g. HBr, HNO₃).
H-Br + H₂O → H₃O⁺ + Br⁻
LEWIS BASES
A Lewis base will have lone-pair electrons. Various species can act as Lewis bases.
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Anions (e.g. OH⁻, CN⁻, CH₃COO⁻)
HO⁻ + H-CN → HO-H + CN⁻ -
Atoms with lone pairs (e.g. NH₃, H₂O:, CO
O=C=O + OH⁻ → HO-C(=O)O⁻ -
Molecules with double or triple bonds (e.g, (CH₃)₂C=CH₂)
(CH₃)₂C=CH₂ + H-Br → (CH₃)₃C⁺ + Br⁻