organic chemistry

organic chemistry

1. CRUDE OIL

   • crude oils is a mixture of hydrocarbons
   • fractional distillation of crude oil
     • 1) crude oil is vapourised , 2) the compounds evaporated and the vapourised crude oil enters the fractioning tower, 3) the smaller the molecules, the lower their boiling point--> the higher they rise in the tower before condensing and being collected as fractions [compounds with the lowest boiling points are obtained at the top of the tower
     • produces more long-chain hydrocarbons (supply greater than demand and less useful) that can be used directly and fewer short- chain hydrocarbons (demand greater than supply, more useful) than required therefore cracking necessary(produces a mixture of alkanes and alkenes of varying lengths
       • cracking process: (thermal decomposition): 1) catalyst mixture of silica [silicon dioxide] and alumina [aluminium oxide]--> porous pot, 2) 600 degrees
     • the mixture of compounds in crude oil is separated because the compounds have different numbers of carbon atoms and therefore have different boiling points and so condense at different temperatures in the tower
     • as you go up the tower the boiling point decreases, the lower the boiling point, the paler in colour, less viscous the liquid, more volatile, more flammable, the clearer the flame on combustion
     • Refinery gases (fuel), Gasoline (petrol), Kerosene (fuel in jet engines), Diesel (fuel in diesel engines), fuel oil (fuel in ships), Residue/ Bitumen (used to make bitumen for surfacing roads

2. incomplete combustion: may produce carbon monoxide which is poisonous because it reduces the capacity of the blood to carry oxygen

3. car engines: temperature reached is high enough to allow nitrogen and oxygen from air to react, forming nitrogen oxides and sulfur dioxides which are pollutant gases that contribute to acid rain

   • Problems of acid rain: corrosion of buildings and metal statues, acidifies lakes: kills equatic animals

4. ALKENES

   • gen
   • unsaturated, double bonds
   • addition of halogens: one product
   • Hydrogenation ( addition og hydrogen)
     • conditions
       • 150 degrees, nickel catalyst
     • margarine manufacture, liquid oils into solid facts

5. TEST FOR UNSATURATED (ALKENES)/ SATURATED (ALKENES) COMPOUNDS

   • 1) addition of bromine water, 2) orange/ brown bromine water is decolourised in alkenes, 3) orange/ brown bromine water would remain its colour in alkanes

6. ALKANES

   • saturated, only single bonds
   • the greater the chain length, the greater the attractions between the molecules (intermolecular forces)--> more difficult it is to overcome therefore the boiling point increases furthermore more energy is requires
   • combustion
     • complete: carbon dioxide and water produced
     • incomplete: carbon monoxide and water produced OR carbon and water produced
   • Substitution reaction: two products
     • alkanes react with halogens in the prescence of UV light

7. ETHANOL

   • alcohols form a homologous series with the functional group -OH
   • manufacture of ethanol
     • passing ethene and steam over a phospheric acid catalyst at a temparature of 300 degrees and pressure of 60-70 atmosphere
       • finite resources (crude oil), continuous flow (more efficient), rapid, produces purer ethanol, high temp. and pressure (high energy input)
     • fermentation of sugars at a temperature of 30 degrees, zymase, sugar sauce, anerobic
       • renewable (sugar cane), batch process (inefficient), slow, produces impure ethanol, general temperature and normal pressure
   • drinks, fuel and slovents
   • dehydration of ethanol produces ethene (hot catalyst--> aluminium oxide)

8. SYNTHETIC POLYMER

   • an addition polymer is formed by joining up many small molecules called monomers they are also hard to dispose of as their inertness means that they do not easily biodegrade
   • uses of polychloroethane (guttering and electrical insulation), uses of polyethene (packaging, electrical insulator, plastic bowl, buckets), uses of polypropene (packaging and ropes)
   • problems with polyalkenes: non- biodegradability and problems of disposal as HCN and HCl can be formed from some polymers, solutions: recycling and production of biodegradable polymers
   • some polymers (e.g. nylon) form by condensation polymerisation--> produces a small molecule e.g. water or hydrogen chloride as well as the polymer

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