Unsaturation

A saturated molecule contains only single bonds. An unsaturated molecule contains one or more multiple (double or triple) bonds. Where more than one multiple bond is present the molecule is said to be polyunsaturated, as in polyunsaturated margarine.

The simplest unsaturated compounds are the alkenes. These are hydrocarbons (that is they contain carbon and hydrogen only). Unsaturated compounds are generally more reactive than saturated ones, as molecules can add across the double bonds.

ethene - the simplest unsaturated compound