chap 11 organic chemistry

• natural gas, methane, and crude oil are non- renewable source of energy
• crude oil is a mixture of hydrocarbons
• describe the fractional distillation of petroleum

  • The crude oil is first heated to 400 degrees to vaporise it which then is passed into the fractionating column
  • The fractionating column is hottest at the bottom and get cooler towards the top
  • The different fractions condense at different levels and are collected at the respective outlet
  • The fractions with higher boiling points condense at higher temperatures and are collected at the lower levels of the fractionating column
  • The fractions with lower boiling points rise further up the column before they condense and are collected
• petroleum gas is fuel for cooking
• petrol is fuel for car engines
• naphtha is feedstock for making petrochemicals such as plastics and detergents
• kerosene is fuel for aircraft engines, cooking using oil stoves and heating
• diesel is fuel for diesel engines in buses, lorries and trains
• lubricating oil is for lubricating machines; for making waves and polishes
• bitumen is for making road surfaces and roofing
• the boiling point increases as the number of carbon atoms in the hydrocarbon increase
• biofules are produced from plants, they are renewable as plants can be grown again
• example of biofules being renewable: Ethanol can be obtained from the fermentation of the sugar in sugarcane plants. As sugarcane plants can be regrown and replaced within a short period of time, the ethanol generated from sugarcane is considered a renewable source
• ethanol produced by plants is called bioethanol
• biofuel is more environmentally sustainable because it is carbon neutral, the carbon dioxide given off during combustion is the same as the carbon dioxide absorbed during photosynthesis. hence, no net emission of greenhouse gas carbon dioxide
• homologous series is a group of compounds with the same general formula, and similar chemical properties because they have the same functional group
• alkanes are homologous series of saturated hydrocarbons with the general formula CnH2n+2
• name this alkane

  methane

  
• name this alkane

  ethane

  
• name this alkane

  propane

  
• name this alkane

  butane

  
• alkanes are generally unreactive because they only consist of strong carbon - carbon single bonds and strong carbon - hydrogen bonds.
• the general formula for an alkane is CnH2n+2.
• when there is a source of ignition, alkanes can undergo combustion.
• alkanes burn in excess oxygen to produce carbon dioxide and water
• there is insufficinet oxygen, incomplete combustion takes place and forms carbon monoxide and carbon (soot)
• alkanes react with halogens, such as chlorine and bromine, in the presence of UV light, which is called substitution reaction
• alkenes are homologous series of unsaturated hydrocarbons
• the general formula for alkenes is CnH2n
• saturated hydrocarbon only contain single covalent bonds between the carbon atoms, bonded to 4 other atoms
• unsaturated hydrocarbon contain double covalent bonds between the carbon atoms, having more atoms being able to be added across the carbon- carbon double bond
• name this alkene

  ethene

  
• name this alkene

  propene

  
• name this alkene

  butene

  
• as molecular size of alkanes increase, their viscosity increase because of the stronger forces of attraction between molecules
• alkanes are insoluble in water but soluble in organic solvents such as tetrachloromethane (CCl4)
• alkenes and alkanes are simple molecular substances with weak forces of attraction between the molecules. hence, alkenes have low melting and boiling points
• as carbon chain of alkenes and alkanes increase, their viscosity increase due to the strong forces of attraction between molecules
• alkenes are insoluble in water but soluble in most organic solvents such as hexane C6H14 and tetrachloromethane CCl4
• liquid alkanes are used as solvents for other organic compounds