CHEMISTRY

• Nomenclature of organic chemicals, up to C8

  • Methane (CH4)
  • Ethane (C2H6)
  • Propane (C3H8)
  • Butane (C4H10)
  • Pentane (C5H12)
  • Hexane (C6H14)
  • Heptane (C7H16)
  • Octane (C8H18)
• Isomers


  Two or more compounds with the same formula but different arrangements of atoms and physical properties
• Isomers


  • C4H10 (butane)
• Chain isomers


  Exist due to the possibility of branching, same molecular formula but different molecular structure
• Position isomers


  For hydrocarbons that contain functional groups, same molecular formula and chain structure but a different position
• Locant


  A figure to indicate the position of a functional group within a molecule
• Position isomers


  • 1-butanol, 2-butanol
• Functional group isomers


  Share the same molecular formula but will have different functional groups, may have different chemical and physical properties
• Functional group isomers


  • Propanal, propanone
• Propanal


  Aldehydes, C=O bond located at the end of the carbon chain, comes from tobacco
• Propanone


  Ketones, C=O bond located in the middle/centre of the carbon chain, powerful organic solvent, commonly known as acetone
• Properties and trends within and between homologous series

  • Physical
  • Chemical
  • Boiling/melting point
  • Intermolecular forces
  • Density
  • Solubility
  • Reactivity
• Trends - chemical


  • Intermolecular
  • Intramolecular
  • Dispersion forces
  • Covalent bonding
  • Dipole-dipole forces
  • O-H bond strength
  • Hydrogen bonding
• Carbon


  In organic compounds, carbons always form four bonds
• Types of carbon bonds

  • Single bonds (C-C)
  • Double bonds (C=C)
  • Triple bonds (C≡C)
• VESPR theory


  Valence shell electron pair repulsion theory, negative charge on electron clouds, bonds repel each other rather than attract
• Tetrahedral shape


  When four single bonds form around a carbon atom, the electrons repel and bonds rearrange symmetrically
• Tetrahedral molecules


  • Carbon tetrachloride
• Diamond


  Hardest natural substance, infinite lattice arrangement of singly bonded carbon atoms, emphasises stability and geometrical symmetry
• Straight chain molecules


  The tetrahedral formation of four single bonds around carbon gives 'straight chained' carbon molecules a zig-zag shape
• Addition reactions


  Reactions in which atoms are added to a molecule by breaking a double or triple bond
• Combustion reactions


  Alkanes and alkenes undergo combustion, energy is often harnessed to power internal combustion engines and industrial furnaces, complete combustion of hydrocarbons produces carbon dioxide
• Hydrogenation


  Addition of hydrogen to a molecule, alkenes are converted to alkanes, occurs in the presence of a metal catalyst
• Hydration


  Addition of water to a molecule, requires a dilute acid catalyst
• Halogenation


  Addition of halogens to a molecule, due to the reactivity of halogens a catalyst is not needed
• Addition of hydrogen halides


  Hydrogen halides are molecules with a hydrogen atom and a halogen atom, common examples are hydrogen chloride and hydrogen bromide
• Incomplete combustion


  Performed with limited oxygen, producing carbon monoxide and carbon, releases less energy per mole of organic compound than complete combustion
• Substitution


  Replacement of an atom on a molecule
• Substitution with halogens


  Only occur with chlorine and bromine, can also occur if the mixture is subjected to UV light, continues until all hydrogen atoms are replaced by halogen atoms
• Reactions of alcohols


  • Combustion
  • Dehydration
  • Substitution
  • Oxidation
• Combustion of alcohols


  Alcohol + Oxygen gas
• The flammability of hydrocarbons decreases as the carbon chain length increases because more covalent bonds need to be broken for the fuel to be broken down