Organic Chemistry - Alkanes and Alkenes Flashcards
What does saturated mean?
There are no double or triple bonds.
• Alkanes are saturated.
What does unsaturated mean?
Contains a double/triple/etc bond.
• Alkenes are unsaturated.
What is general formula for Alkanes?
CnH2n+2
What is the general formula for Alkenes?
CnH2n
What are isomers?
Molecules with the same molecular formula, but different structural formulae.
What happens when methane reacts with bromine in the presence of UV light?
bromomethane is formed
What does homologous series mean?
A homologous series is “family” of organic compounds which:
- contain the same functional group therefore similar chemical properties
- differ from one another by CH₂
- because they get larger they have a trend in physical properties (like the fractions in crude oil)
How to test for an Alkenes?
Add ethene to bromine water, shake it, and it will become colourless. Addition reaction.
How can polymers be made?
- addition polymerisation
- condensation polymerisation
What is addition polymerisation?
The joining together or many small molecules called monomers.
What is condensation polymerisation?
• Two different monomers are added to create a polymer, which also produces a small molecule, which is normally water, but sometimes HCl.
What’s an example of condensation polymerisation?
• The making of nylon.
How can ethanol be produced?
- fermentation
- production from ethene
Uses of polypropene
- ropes
- crates
Uses of polyethene
- plastic bags
- plastic bottles
Uses of polychloroethene
- drainpipes
- replacement windows
What are the problems associated with disposing of polymers?
- Polymers or plastics cannot be broken down due to their many strong covalent bonds they are inert (unreactive).
- The methods of disposal are landfill or incineration.
What does biodegradable mean?
Something which can decompose in the ground and is broken down by living organisms/bacteria.
What happens during the hydration of ethene?
- Ethene and steam are passed over phosphoric acid (acts as a catalyst) to create ethanol.
- Temperature is about 300ºC.
- Pressure is at about 60-70 atmospheres.
- C2H4 + H2O → C2H5OH.
What happens during the manufacture of ethanol using fermentation?
- A sugar (e.g. glucose) in converted into ethanol using yeast.
- The temperature is about 30ºC.
- The pressure is normal.
What are the advantages of producing ethanol by hydration?
- Quite chea__p because ethene (which comes from crude oil) is not very expensive and not much is wasted.
- The rate of reaction is very fast.
- The product made is of a very high quality (pure).
- Low labour costs.
What are the disadvantages of producing ethanol using hydration?
- Ethene comes from crude oil, which is a finite resource and therefore will run out.
- The process is done at a high temperature and high pressure and it is a continuous process, so the equipment needed is expensive.
What are the advantages of fermentation to produce ethanol?
- Sugar and yeast are both renewable resources.
- Equipment needed is quite basic and quite cheap.
What are the disadvantages of fermentation to produce ethanol?
- The ethanol is impure (and not very concentrated) and needs to be distilled and purified.
- The rate of reaction is very slow.
- It is done as a batch process and therefore labour costs are quite expensive.
What happens during the dehydration of ethanol?
- The water is removed from ethanol to produce ethene in a dehydration reaction.
- Ethanol vapour is passed over a hot catalyst of aluminium oxide (Al2O3) which provides a large surface area for the reaction.
- C2H5OH → C2H4 + H2O
What is made during the complete combusion of alkanes?
Complete combusion occurs when there is plenty of oxygen to burn with the alkane.
- alkane + oxygen → carbon dioxide + water (+ energy)
- CH4 + 2O2 → CO2 + 2H2O
What is made during the incomplete combustion of alkanes?
Incomplete combustion occurs when there is not enough oxygen to burn with the alkane.
- alkane + oxygen → carbon + carbon monoxide + carbon dioxide + water (+ energy)
- the symbol equation depends on how much oxygen is present
What would the repeat unit for poly(ethene) look like?
What would the repeat unit for poly(propene) look like?
What would the repeat unit for poly(chloroethene) look like?
Complete the chemical equation for the reaction between ethene and bromine water
C2H4 + Br2 →
C2H4Br2
Why is the second method a safer way to measure the boiling points of organic compounds?
Organic compounds are flammable, so the second method reduces the risk of fire.
What is a raw material which can be used as a source of C6H12O6?
Cane sugar / sugar beet.
