Chemistry- Organic Chemistry

• Organic chemistry


  The chemistry of the compounds of carbon, excluding carbonates, oxides of carbon, hydrogen carbonates and carbon itself.
• Organic compounds


  Made up of chains of carbon atoms covalently bound together, always containing hydrogen atoms, may also contain other atoms like chlorine, oxygen or nitrogen.

  
• Carbon


  • Has the ability to form strong covalent bonds with other carbon atoms
  • Can form straight chains
  • Can form branched chains
  • Can form rings

  
• Methane


  The simplest organic compound, with the chemical formula CH4

  
• Every carbon atom in a hydrocarbon must have four bonds

  
• Homologous series


  A family of organic compounds which have a particular characteristic group and exhibit similar properties, with a common general formula
• Alkanes


  Simple hydrocarbons, also known as saturated hydrocarbons, containing only carbon-to-carbon single bonds, with the general formula CnH2n+2

  
• Properties of alkanes


  • Liquid alkanes float on water (low density)
  • Alkanes are saturated compounds
  • Methane is found in natural gas
  • Bottled gas is a mixture of alkanes (mostly butane)
  • Boiling point increases with increasing molecular size

  
• Branching in alkanes


  Lowers the boiling point
• Isomers


  Compounds with the same molecular formula but different structural formula, having different chemical and physical properties
• Naming branched alkanes


  1. Identify the longest straight chain

  2. Note the type of bonds (single bonds = -ane)

  3. Name the branches (CH3 = methyl, C2H5 = ethyl)

  4. Number the carbon atoms so the branch has the smallest possible number

  
• Solubility of alkanes


  Insoluble in water (non-polar), soluble in non-polar solvents

  
• Reactions of alkanes


  1. Combustion in air to produce CO2 and H2O (complete combustion)

  2. Combustion in limited air to produce CO and H2O (incomplete combustion)

  3. Substitution reaction with halogens in UV light

  
• Halogenoalkanes


  Products of the substitution reaction of alkanes with halogens

  
• Refining of crude oil


  Separation of crude oil into fractions by fractional distillation

  
• Fractions obtained from crude oil refining

  • Refinery gases (C1-C4)
  • Gasoline (C5-C6)
  • Naphtha (C6-C10)
  • Kerosene (C10-C16)
  • Diesel oil (C16-C20)
  • Lubricating oil (C20-C30)
  • Fuel oil (C30-C40)
  • Bitumen (C50+)

  
• Cracking of crude oil


  1. Thermal cracking (by heating)

  2. Catalytic cracking (using a catalyst)
• Cracking of long chain alkanes always leads to the formation of at least one unsaturated product

  
• The combustion of alkanes is very exothermic and they are mainly used as fuels
• Alkanes can be used to obtain other chemicals, such as hydrogen

  
• Bitumen


  C50 upwards, Solid residue
• Bitumen is used for road surfacing
• Cracking of crude oil


  1. Crude oil contains many long-chain alkanes

  2. Cracking is a process to produce larger quantities of shorter chain hydrocarbons

  3. Cracking can be thermal or catalytic
• Thermal cracking


  Carried out by simply heating
• Catalytic cracking


  Carried out by using a catalyst
• The cracking of a long chain alkane always leads to the formation of at least one unsaturated product

  
• Uses of alkanes


  • Combustion as fuels
  • To obtain other chemicals
  • As solvents
• Alkenes


  Homologous series of compounds with at least one carbon-carbon double bond

  
• First 6 members of the alkene family

  • Ethene
  • Propene
  • Butene
  • Pentene
  • Hexene

  
• Alkenes


  • Unsaturated molecules due to the presence of double bonds
  • More reactive than alkanes due to the double bonds

  
• Lab preparation of ethene


  1. Dehydration of ethanol using concentrated sulfuric acid

  2. Dehydration of ethanol using alumina or porous pot (catalytic dehydration)

  
• Ethanol dehydration using concentrated sulfuric acid


  Produces ethene and water
• Ethanol dehydration using alumina or porous pot


  Produces ethene and water

  
• Cracking of alkanes


  • C12H26 to C8H18 + C4H8
  • C8H18 to C6H14 + C2H4

  
• Air pollutants


  • Sulfur dioxide
  • Carbon monoxide
  • Carbon dioxide
  • Oxides of nitrogen
  • Tiny solid particles
  • Crude oil spillages
• Combustion of alkenes


  Produces carbon dioxide and water, with some soot
• Addition reactions of alkenes

  1. Hydrogenation

  2. Halogenation

  3. Hydrohalogenation

  4. Hydration

  
• Polymerisation


  Alkene molecules add to each other forming long-chain molecules called polymers

  
• Addition polymers


  • Polyethene
  • Polyvinylchloride (PVC)
  • Polytetrafluoroethene (PTFE)

  
• Alkynes are another homologous series of unsaturated hydrocarbons that contain a triple bond