Functional Groups (AQA AS Chemistry): Revision Note

Organic Definitions & Terminology

• Organic chemistry is the study of carbon-containing compounds

• Carbon forms a vast number of compounds because it can form strong covalent bonds with other carbon atoms, a property known as catenation

• This allows carbon atoms to form long chains and rings, resulting in a very large number of possible carbon compounds

Homologous series

• A homologous series is a group of organic compounds that have the same functional group, but each successive member differs by CH₂

Homologous Series of Alkanes

• Things that can be said about a homologous series:

  • Each member has the same functional group

  • Each member has the same general formula

  • Each member has similar chemical properties

  • Each successive member differs by  -CH₂ –

  • Members have gradually changing physical properties, for example, boiling point, melting point, and density

• As a homologous series is ascended, the size of the molecule increases

• This affects the physical properties, such as boiling point and density

Functional Groups

• Functional groups determine the physical and chemical properties of molecules

• The table below shows a summary of common functional groups found in compounds

• R is any other atom or group of atoms (except for hydrogen)

Functional Groups found in Compounds Table

Hydrocarbons

• Hydrocarbons are compounds that are made up of carbon and hydrogen atoms ONLY

• Ethanol is NOT a hydrocarbon, as the molecule also contains an oxygen atom and is not solely made up of carbon and hydrogen