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C7 - Organic Chemistry (Alkanes (Complete combustion (Hydrocarbon + oxygen…
C7 - Organic Chemistry
Crude Oil
Is a fossil fuel (non-renewable, finite), formed from the remains of biomass (mainly of plankton) that was buried underground (due to the high pressure and temperature)
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Uses:
-Fuel for modern transport
-Petrochemical industry (for poluymers, solvents, lubricants and detergents) #
Fractional Distillation
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Energy can break intermolecular bonds (bonds between the chains)
Intramolecular bonds can never be broken (bonds between the carbon)
As heat increases, the atoms in the chain change state (evaporate) and break the intermolecular bonds
When the chain is longer, there are more intermolecular forces to break and therefore more heat is required.
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Cracking
After fractional distillation, a lot of long-chain hydrocarbons are produced which aren't useful
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Alkanes and alkenes are the products of cracking. Alkenes are useful as they aere the starting material when making lots of other compounds, eg. polymers
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eg. Decane is a long-chain hydrocarbon (found in crude oil) and can be broken up to make octane (useful for petrol) and ethene (for making plastics)
Alkanes
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Hydrocarbon properties
As the length of the carbon chain changes, the properties also change
Short-chain hydrocarbons are less viscous, more volatile and more flammable
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- Methane CH4
- Ethane C2H6
- Propane C3H8
- Butane C4H10
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The number of bonds an element can make is based on its group (carbon is in group 4 so can make 4 bonds)
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Alkenes
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They are more reactive than alkanes because the double bond can open up and react with other atoms #
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- Ethene C2H4
- Propene C3H6
- Butene C4H8
- Pentene C5H10
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Reactions
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Hydrogenation
Hydrogen reacts (in the presence of a catalyst) with the double-bonded carbons to open up the double bond and form an alkane
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Alcohols
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The steam is the source of the OH, the functional group for alcohols
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Once the reaction has taken place, the mixture is passed from the reactor into a condenser. Ethanol and water have higher boiling points than ethene so they both condense and the unreacted ethene gas is recycled back to the reactor. The alcohol can then be purified from the mixture by fractional distillation
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React in addition reactions with halogens, eg. bromine, chlorine and iodine
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Functional group - a group of atoms in a molecule that determine how that molecule typically reacts (the bit that does the reacting)
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To make a polymer (polymerisation) via an addition reaction we need an unsaturated hydrocarbon (alkene) (addition polymerisation)
Where the double bond breaks, each carbon joins to another monomer unit (which requires high pressure, heat and a catalyst
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- Methanol CH3OH
- Ethanol C2H5OH
- Propanol C3H7OH
- Butanol C4H9OH
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Alcohols are used as solvents and fuels because they can't dissolve most things water can dissolve and vice versa (eg. hydrocarbons, oils and fats)
Fermentation
Ethanol, found in alcoholic drinks, can be made by fermentation
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Occurs fastest at around 37C in a slightly acidic solution under anaerobic conditions (no oxygen)
Yeast must be present - it is a biological catalyst
If these conditions changed, the enzyme could be denatured or work at a slower rate
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Carboxylic Acids
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React like other acids
React with carbonates to produce a salt, water and carbon dioxide
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- Methanoic Acid HCOOH
- Ethanoic Acid CH3COOH
- Propanoic Acid C2H5COOH
- Butanoic Acid C3H7COOH
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