Hydrocarbons - Topic 9 Flashcards
What are the first 4 alkanes?
- methane
- ethane
- propane
- butane
What is the general formula of alkanes?
Why are alkanes saturated hydrocarbons
- alkanes are saturated as they only contain single bonds in the molecule
- contain no C=C double bonds
- are compounds made of hydrogen and carbon only
Structure of alkenes in comparison to alkanes:
Why are alkenes unsaturated?
contain double carbon bond C=C
What is the functional group of alkenes?
C=C
Addition reaction of ethene + bromine:
Ethene + bromine -> 1,2-dibromoethane
What happens to the double bond C=C in the ethene + bromine reaction?
the C=C bond is broken which allows the Br2 molecules to bond to C forming 2 x C-Br molecules
How is bromine water used to distinguish between alkanes and alkenes?
- alkenes react with bromine water turning it from orange to colourless
- react at room temperature
- alkanes do not react with bromine water
- alkanes can only undergo a substitution reaction
- in UV light
- one Br will substitute into alkane + other Br produces HBr
What does the complete combustion of alkanes and alkenes involve?
- the complete combustion of alkanes and alkenes involves the oxidation of the hydrocarbons to produce carbon dioxide and water
- the combustion of hydrocarbons releases energy
Equation for complete combustion of alkanes and alkenes:
alkane/alkene + oxygen → carbon dioxide + water
Methane molecular formula + displayed formula:
Propane molecular formula + displayed formula:
Butane molecular formula + displayed formula:
Ethene molecular formula + displayed formula:
Propene molecular formula + displayed formula:
Butene molecular formula + displayed formula:
How do you draw branched alkanes?
2-methylbutane
- 2 indicates the position of the branch
- methyl indicates that there is only one carbon in the branch
2,2-dimethylbutane
- 2,2 position of each carbon branches
- di indicates that there are 2 carbon branches
- methyl indicates that there is only one carbon in each of the 2 branches
Why do alkenes react with bromine solution and not alkanes?
- alkenes react with bromine solution as they are unsaturated
- alkanes don’t react with bromine solution as they are saturated
Ethane molecular formula + displayed formula:
