Organic Chem

• Crude oil is a mixture of different hydrocarbons that can be separated into the separate molecules by fractional distillation as the different chain lengths of molecules result in them having different boiling points.
• In the process of fractional distillation, the mixture is vapourised and fed into the fractionating column.
• Vapours rise, cool and condense in the fractionating column.
• Products are siphoned off for different uses in the fractionating column.
• Products with short carbon chains have lower boiling points, meaning they rise higher up the column before reaching their boiling point and are collected at the top of the column.
• Products with long carbon chains have higher boiling points, meaning they don’t rise very far up the column before reaching their boiling point and condense and are collected at the bottom of the fractionating column.
• The compounds collected from the fractionating column are then broken down further via the method of cracking.
• Longer carbon chains are not very useful, therefore they are broken down to form smaller, more useful molecules.
• The carbon-carbon bonds are broken in order to do this, which require quite harsh reaction conditions.
• There are two main types of cracking which result in slightly different organic compounds: Thermal Cracking and Catalytic Cracking.
• Thermal Cracking produces a high proportion of alkanes and alkenes and requires high temperatures around 1200 K and pressures around 7000 kPa.
• Catalytic Cracking produces aromatic compounds with carbon rings and requires lower temperatures around 720 K, but a zeolite catalyst is needed to compensate for these less harsh conditions.
• Alkanes make good fuels as they release a lot of energy when burned and with sufficient oxygen present, they undergo complete combustion to produce carbon dioxide and water.
• Termination - two radicals join to end the chain reaction and form a stable product.
• Free radicals are shown using a dot.
• The propagation step can continue many times to result in multiple substitutions, this is a chain reaction.
• Both of these gaseous products can be removed from systems using a catalytic converter.
• The UV light breaks down the halogen bonds producing reactive intermediates called free radicals.
• Condition of the reaction can be altered to favour the termination step and limit the number of substitutions.
• Carbon monoxide is a toxic gaseous product which is especially dangerous to humans as it has no odor or colour.
• Alkanes react with halogens in the presence of UV light to produce halogenoalkanes.
• Sulfur impurities can lead to the acidification of water in the Earth’s atmosphere as they react to form a weak form of H2SO4.
• Unless removed from the waste products in industry, these can cause serious respiratory problems as they pollute the air.
• Propagation - a hydrogen is replaced and the Cl• radical reformed as a catalyst.
• Incomplete combustion can also produce carbon particulates, small fragments of unburned hydrocarbon.
• Calcium oxide and gypsum are used in the flue gas desulfurisation process.
• Initiation - the halogen is broken down.
• Oxides of nitrogen are also produced as a byproduct of alkane combustion.
• A rhodium catalyst is used in a catalytic converter to convert harmful products into more stable products such as CO2 or H2O.
• The impurities can be removed from waste products via flue gas desulfurisation.
• Unless treated or removed, all of these pollutants can contribute to global warming, acid rain and health issues in humans.
• If the oxygen present is insufficient, combustion is incomplete and carbon monoxide is produced alongside water.
• These attack the alkanes resulting in a series of reactions; initiation, propagation and termination.