pricin banner

Questions & Answers

What is an unsaturated hydrocarbon?

An unsaturated hydrocarbon contains at least one carbon carbon double bond, such as alkenes which contain the C=C functional group. Due to the presence of the double bond, these compounds are more reactive and can undergo various chemical reactions, including addition and polymerization reactions. In these reactions, the C=C is converted into a C-C single bond, allowing one additional atom or group to be added to each carbon atom, since it frees up electrons of the carbon to be used up in new covalent bonding with other atoms/groups. 

Other unsaturated hydrocarbons include alkynes, which have a carbon-carbon triple bond, and aromatic hydrocarbons, which are ring shaped and contain more than one C=C. To check the presence of an unsaturated hydrocarbon, bromine water is added to it. If the bromine water is decolourised (changes from brown to colourless), it indicates the presence of unsaturated hydrocarbons, as the double bond breaks and Br atoms are added to the carbons in an addition reaction. This is a common test to distinguish between an alkane (saturated hydrocarbon) and an alkene (unsaturated hydrocarbon).

Helpful Content:

Related Chemistry GCSE answers