Functional groups in organic chemistry (A level chemistry)

Functional groups in organic chemistry (A level chemistry)

Organic molecules with the same functional group react in the same
way, no matter the length of the hydrocarbon chain. This means that if you learn the reactions of one alkane, such as ethane, you can perfectly well apply this knowledge to predict the reactions of any other alkane.

The table below shows some families of organic compounds and their functional groups.

Homologous series and functional groups

Any homologous series has the following characteristics:

• compounds in the homologous series have the same general formula.
• each member of the homologous series differs from the next by CH₂.
• the length of the carbon chain has little to no effect on the chemical reactivity of the members of a series.
• while the functional group affects the chemical properties, the length of the carbon chain affects physical properties, such as melting point, boiling point, and solubility.
• melting points and boiling points of members of a homologous series tend to increase by a small amount as the number of carbon atoms in the chain increases. This is due to the increase in the intermolecular forces.
• branching of the carbon chain reduces the melting and boiling points.

General formula of organic compounds

Each member of a homologous series adheres to a certain general formula which shows the ratio of its atoms. The table below shows the general formulae of some functional groups.