Introduction to Alkenes
Chemistry: AQA A Level, topic 5.4.1
Alkenes
Alkenes are hydrocarbons with the functional group C=C. This means that alkenes have a carbon-carbon double bond.
Unsaturated
- Alkenes are unsaturated hydrocarbons because they contain a double bond between two of their carbon atoms (C=C).
- This means that an alkene contains two fewer hydrogen atoms than the alkane with the same number of carbon atoms.
Formula
- A homologous series is a series of compounds with the same general formula.
- CnH2n is the general formula for alkenes.
Reactive
- Alkenes are more reactive than alkanes.
- This is because the double bond is of high electron density.
The Four Shortest Alkenes
The four shortest alkenes, in ascending (increasing) size order, are:
Ethene
- Ethene has the formula C2H4.
Propene
- Propene has the formula C3H6.
Butene
- Butene has the formula C4H8.
Pentene
- Pentene has the formula C5H10.
Test yourself on Introduction to Alkenes
Which of the following are properties of alkenes?
Why are alkenes more reactive than alkanes?
Why are alkenes more reactive than alkanes?
What is the shortest alkene?
Which alkene has one more carbon atom in its formula than propene?