Cambridge IGCSE Chemistry · Syllabus 0620 · Organic Chemistry
Functional Group
What is Functional Group?
An atom, or group of atoms, that determines the chemical properties of a homologous series, such as the C=C of an alkene, the -OH of an alcohol or the -COOH of a carboxylic acid.
This definition is part of the Organic Chemistry chapter in Cambridge IGCSE Chemistry.
Functional Group in context
Organic chemistry is the chemistry of carbon compounds. Every question in Topic 11 is the same question in a different costume: read the carbon backbone, find the functional group, name or draw the molecule, choose the reaction and its conditions, then redraw only the part that changed and check that every atom still has the right number of bonds.
Common mistakes with Functional Group
- “All polymerisation reactions release water.” Supplement 11.8.9 why it fails This over-generalises from condensation polymers to every polymer. correct Addition polymerisation releases nothing at all — the polymer is the only product. Condensation polymerisation releases a small molecule, and you can only say which one by looking at the functional groups actually being joined. Taught in Lesson 11.8D.
- 17. “Nylon is made from ethanoic acid and an amine.” Supplement 11.8.8 defect Condensation monomers given only one functional group each. why With one reactive end apiece, the two would join once and stop. You would get a small molecule, not a polymer. repair Use a dicarboxylic acid and a diamine: HOOC–□–COOH and H2N–▢–NH2. transfer Explain why an amino acid can build a protein on its own, despite there being only one kind of monomer.