Topic 18.1: Acids and bases – Lewis acids and bases
The acid–base concept can be extended to reactions that do not involve proton transfer.
• Understanding: A Lewis acid is a lone pair acceptor and a Lewis base is a lone pair donor.
▪ Lewis acid: substance that can accept a pair of electrons (lone pair acceptor)
▪ Lewis base: substance that can donate a pair of electrons (lone pair donor)
• Understanding: When a Lewis base reacts with a Lewis acid a coordinate bond is formed.
▪ Lewis acid-base reaction: coordinate bond is formed in a Lewis acid-base reaction
• Example: in acid-base reaction of BF3 and NH3, BF3 acts as a Lewis
acid while NH3 acts as a Lewis base
• Lone pair of the nitrogen atom forms a covalent bond with the empty
hybridized orbital of the boron atom
• Understanding: A nucleophile is a Lewis base and an electrophile is a Lewis acid.
▪ Nucleophile: substance that provides a pair of electrons to form a new covalent bond (Lewis base)
▪ Electrophile: substance that accepts a pair of electrons to form a new covalent bond (Lewis acid)
• Applications and skills: Application of Lewis’ acid–base theory to inorganic and organic chemistry to identify the role of the
reacting species.
▪ Inorganic application: transition metal complexes
• Lewis acid: transition elements; have a partially occupied d subshell and can accept electron pairs
• Lewis base: ligands; possess a lone pair of electron form complex ions through coordinate bond
▪ Organic application: nucleophiles and electrophiles in organic substitution reaction
• Lewis acid: electrophiles; electrophilic addition in alkenes (accepts pair of electron), substitution in benzene
• Lewis base: nucleophiles; nucleophilic substitution reactions (donates pair of electrons)
• Nature of science: Theories can be supported, falsified or replaced by new theories—acid–base theories can be extended to a wider
field of applications by considering lone pairs of electrons. Lewis theory doesn't falsify Brønsted–Lowry but extends it.
• International mindedness: Acid–base theory has developed from the ideas of people from different parts of the world through both
collaboration and competition.
• Guidance: Both organic and inorganic examples should be studied.
• Guidance: Relations between Brønsted–Lowry and Lewis acids and bases should be discussed. International-mindedness:
The acid–base concept can be extended to reactions that do not involve proton transfer.
• Understanding: A Lewis acid is a lone pair acceptor and a Lewis base is a lone pair donor.
▪ Lewis acid: substance that can accept a pair of electrons (lone pair acceptor)
▪ Lewis base: substance that can donate a pair of electrons (lone pair donor)
• Understanding: When a Lewis base reacts with a Lewis acid a coordinate bond is formed.
▪ Lewis acid-base reaction: coordinate bond is formed in a Lewis acid-base reaction
• Example: in acid-base reaction of BF3 and NH3, BF3 acts as a Lewis
acid while NH3 acts as a Lewis base
• Lone pair of the nitrogen atom forms a covalent bond with the empty
hybridized orbital of the boron atom
• Understanding: A nucleophile is a Lewis base and an electrophile is a Lewis acid.
▪ Nucleophile: substance that provides a pair of electrons to form a new covalent bond (Lewis base)
▪ Electrophile: substance that accepts a pair of electrons to form a new covalent bond (Lewis acid)
• Applications and skills: Application of Lewis’ acid–base theory to inorganic and organic chemistry to identify the role of the
reacting species.
▪ Inorganic application: transition metal complexes
• Lewis acid: transition elements; have a partially occupied d subshell and can accept electron pairs
• Lewis base: ligands; possess a lone pair of electron form complex ions through coordinate bond
▪ Organic application: nucleophiles and electrophiles in organic substitution reaction
• Lewis acid: electrophiles; electrophilic addition in alkenes (accepts pair of electron), substitution in benzene
• Lewis base: nucleophiles; nucleophilic substitution reactions (donates pair of electrons)
• Nature of science: Theories can be supported, falsified or replaced by new theories—acid–base theories can be extended to a wider
field of applications by considering lone pairs of electrons. Lewis theory doesn't falsify Brønsted–Lowry but extends it.
• International mindedness: Acid–base theory has developed from the ideas of people from different parts of the world through both
collaboration and competition.
• Guidance: Both organic and inorganic examples should be studied.
• Guidance: Relations between Brønsted–Lowry and Lewis acids and bases should be discussed. International-mindedness:
