• Hydrocarbons?are compounds containing hydrogen and carbon only
• There are four families of hydrocarbons you should know:?alkanes, alkenes, alkynes?and?arenes
• Alkanes?have the general molecular formula?C_nH_2n+2. They contain only single bonds and are said to be saturated
• Alkanes?are named using the nomenclature rule?alk + ane
• The?alk?depends on the number of carbons as outlined in the previous Section 10.1.2

The first six members of the alkane family

• Alkenes?have the general molecular formula?C_nH_2n
• They are said to be?unsaturated
• Alkenes are named using the nomenclature rule?alk + ene
• In molecules with a straight chain of 4 or more carbon atoms, the position of the C=C double bond must be specified
• The carbon atoms on the straight chain must be numbered, starting with the end closest to the double bond
• The lowest-numbered carbon atom participating in the double bond is indicated just before the -ene:

The first five members of the alkene family

• There is a distinction to be made between the name of the?functional group?and the name of the?family
• The name of the family is?alkene, but the name of the functional group is?alkenyl

• Alkynes?have the general molecular formula?C_nH_2n-2
• The triple bond makes them?unsaturated?molecules
• Alkynes?are named using the nomenclature rule?alk + yne
• As with alkenes, in molecules with a straight chain of 4 or more carbon atoms, the position of the triple bond must be specified
• The carbon atoms on the straight chain must be numbered, starting with the end closest to the triple bond
• The lowest-numbered carbon atom participating in the triple bond is indicated just before the -yne:

The first five members of the alkyne family

• The name of the functional group is?alkynyl

• Arene?is the collective name given to compounds with one or more rings with?pi electrons?that are?delocalised?throughout the ring(s)
• Compounds with this feature are said to be?aromatic
• This doesn't mean they are necessarily smelly, although a lot of naturally occurring arenes do have distinctive smells!

Arenes are present in many everyday chemicals and pharmaceuticals

• Benzene,?C₆H₆, is the only?aromatic?hydrocarbon?that is covered in IB Chemistry and is dealt with in Section 10.1.12
• The functional group in?benzene?is known as a?phenyl group?when attached to other molecules