Organci chemistry

• Crude oil is a finite resource found in rocks
• Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
• Crude oil is a mixture of a very large number of compounds
• Most compounds in crude oil are hydrocarbons, which are molecules made up of hydrogen and carbon atoms only
• Most hydrocarbons in crude oil are alkanes
• The general formula for the homologous series of alkanes is CnH2n+2
• The first four members of the alkanes are methane, ethane, propane, and butane
• Alkane molecules can be represented in the form C2H6
• Crude oil can be separated into fractions through fractional distillation, with each fraction containing molecules with a similar number of carbon atoms
• These fractions can be processed to produce fuels and feedstock for the petrochemical industry
• Fuels like petrol, diesel oil, kerosene, heavy fuel oil, and liquefied petroleum gases are produced from crude oil
• The petrochemical industry produces materials essential for modern life, such as solvents, lubricants, polymers, and detergents
• The vast variety of natural and synthetic carbon compounds is due to the ability of carbon atoms to form families of similar compounds
• Some properties of hydrocarbons depend on the size of their molecules, including boiling point, viscosity and flammability. These properties influence how hydrocarbons are used as fuels.
• Crude oil can be separated into fractions through fractional distillation, with each fraction containing molecules with a similar number of carbon atoms
• These fractions can be processed to produce fuels and feedstock for the petrochemical industry
• Fuels like petrol, diesel oil, kerosene, heavy fuel oil, and liquefied petroleum gases are produced from crude oil
• The petrochemical industry produces materials essential for modern life, such as solvents, lubricants, polymers, and detergents
• The vast variety of natural and synthetic carbon compounds is due to the ability of carbon atoms to form families of similar compounds
• Each alkane has a boiling point that is higher than the one before it As the molecules get larger, the intermolecular forces of attraction between the molecules becomes greater as there are more electrons in the molecules and greater surface area contact between them This means that more heat is needed to separate the molecules, hence with increasing molecular size there is an increase in boiling point
• Viscosity refers to the ease of flow of a liquid.High viscosity liquids are thick and flow less easily.The opposite of high viscosity is to say a liquid is runny
• Viscosity also increases with increasing chain length.This is also due to the increased intermolecular forces of attraction as molecular size increases.Increased viscosity means that longer chained alkanes are useful as lubricants in machinery as they are less likely to burn and function to reduce friction between moving parts
• Molecular size again influences the ease of ignition or flammability of hydrocarbons Smaller hydrocarbon molecules are more flammable and are easier to ignite than larger molecules This makes them very useful as fuels, releasing large amounts of energy when they burn
• Molecular size again influences the ease of ignition or flammability of hydrocarbons Smaller hydrocarbon molecules are more flammable and are easier to ignite than larger molecules This makes them very useful as fuels, releasing large amounts of energy when they burn
• Hydrocarbons undergo combustion in the presence of air
• Complete combustion forms water and carbon dioxide gas
• Carbon and hydrogen from the fuel are oxidised/gain oxygen:
• Hydrogen oxidises to form water
• Carbon oxidises to form carbon dioxide
• Example of combustion: methane (CH4) burns as follows:

  CH4 + 2O2 → CO2 + 2H2O
• Petrol is largely composed of isomers of octane, C8H18, which requires large amounts of oxygen to combust fully
• Combustion of octane:

  2C8H18 + 25O2 → 16CO2 + 18H2O
• Car engines' efficiency does not usually enable all the petrol to burn
• Car exhaust contains small amounts of unburnt hydrocarbons, carbon monoxide, and soot
• Carbon dioxide produced is a major contributor to global warming
• Replacement of combustion engines with electric vehicles is a major ongoing challenge for all countries
• Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules. Cracking can be done by various methods including catalytic cracking and steam cracking
• Catalytic cracking uses a temperature of approximately 550°C and a catalyst. known as a zeolite which contains aluminium oxide and silicon oxide. Steam cracking uses a higher temperature of over 800°C and no catalyst.
• Alkenes are more reactive than alkanes and react with bromine water, which is used as a test for alkenes.Bromine water is an orange solution of bromine. It becomes colourless when it is shaken with an alkene. Alkenes can decolourise bromine water, but alkanes cannot.
• There is a high demand for fuels with small molecules and so some of the products of cracking are useful as fuels. Alkenes are used to produce polymers and as starting materials for the production of many other chemicals.