What is here?
The models show unbranched members of this series with 2, 3 or 4 carbon atoms. You can also see the structural and displayed formulae for these alkenes.
A homologous series is a series of compounds which:
- have the same functional group
- have the same general formula
- differ by CH2 in molecular formulae from neighbouring compounds
- show a gradual variation in physical properties, such as their boiling points
- have similar chemical properties.
A functional group is an atom, group of atoms or a bond responsible for the characteristic chemical reactions of a substance. The functional group in alkenes is the double carbon–carbon double bond, C=C.
A general formula is a chemical formula used to represent the members of a homologous series. The general formula for the alkanes is CnH2n.
Hexene molecules, for example, contain six carbon atoms:
n = 6
2n = (2 × 6) = 12
So the molecular formula for hexene is C6H12.
Name of alkene
The model and displayed formula of but-2-ene show trans-but-2-ene. This is one isomer of but-2-ene. The other isomer is cis-but-2-ene. Find out about cis-trans isomers here.