Introduction

• A hydrocarbon is a compound of carbon and hydrogen only
• An isomer is an atom with the same molecular formula, but different bond placements (different structural formula)
• A homologous series is a group of compounds that can be represented with the same general formula
• A functional group is a particular group of atoms which are responsible for how the molecule reacts
• Meth- 1C

  Eth- 2C

  Prop- 3C

  But- 4C

  Pent- 5C

  Hex- 6C
• In a substitution reaction an atom or group of atoms is replaced by a different atom or group.
• An addition reaction occurs when an atom or group of atoms is added to a molecule without taking anything away
• A combustion reaction is a reaction with oxygen, and it is when excess oxygen gives the products water and carbon dioxide, and also heat energy
• The molecular formula shows the actual number of atoms of each element in a molecule.
• The empirical formula shows the simplest whole number ratio of atoms present in a compound. So the molecular formula is a multiple of the empirical formula.
• The general formula shows the relationship between the number of atoms of one element to another within a molecule. Members of a homologous series share the same general formula. The general formula for alkanes is CnH2n+2 and the general formula for alkenes is CnH2n.
• A structural formula shows how the atoms in a molecule are joined together.
• The displayed formula is a full structural formula which shows all the bonds in a molecule as individual lines.

   
• The terms above are demonstrated with the example of butane.

  • Molecular formula: C₄H₁₀
  • Empirical formula: C₂H₅
  • General formula (alkanes): CnH2n+2
  • Structural formula: CH₃ – CH₂ – CH₂ – CH₃
• What does the molecular formula describe?

  The actual number of each type of atom
• What does a molecular formula of C₆H₁₂ indicate?

  6 carbon atoms and 12 hydrogen atoms
• What information does the molecular formula NOT provide?

  How the atoms are arranged in the molecule
• What do structural and displayed formulas indicate?

  How the atoms are arranged in a molecule
• What can be inferred if only a molecular formula is given?

  There may be several possible structural formulas