C7: Alkanes, Alkenes and Alcohol

C7: Alkanes, Alkenes and Alcohol

1. Alkanes

   • A group of hydrocarbons
     • In this group atoms are joined together by single carbon-carbon bonds
   • Are saturated carbons
     • This is because they contain only single bonds and can't make anymore
   • Do not react well with aqueous solutions
     • The C-C and C-H bonds are too strong and unreactive
     • They burn well in plenty of air to produce carbon dioxide and water
       • An example of a balanced equation of combustion of an Alkane would be:
         • C3H8 + 5O2 = 3CO2 + 4H2O
         • CH4+ 2O2 = CO2 + 2H2O
   • The general formula for an alkane is CnH(2n+2) where "n" is the number of carbon atoms
     • Methane
       • CH4
     • Ethane
       • C2H6
     • Propane
       • C3H8
     • Butane
       • C4H10

2. Alkenes

   • A group of hydrocarbons
     • Their atoms are joined together in reactive C=C bonds
   • they are unsaturated because the atoms can stil react
   • The general fomula for Alkenes is CnH(2n^3) Where "n" is the number of carbon atoms
     • Methene
       • CH8
     • Ethene
       • C2H64
     • Propene
       • C3H216
     • Butene
       • C4H512

3. Alcohols

   • Characteristics are due to their functional group -OH
   • The general formula for Alcohols is CnH(2n+1)OH where "n" is the number of carbon atoms
     • Methanol
       • CH3OH
       • Can be used as:
         • Chemical feedstock
         • Cosmetics manufacturing
     • The two simplest alcohols are methanol and ethanol.
     • Ethanol
       • C2H5OH
       • Can be used as:
         • A solvent
         • A fuel
   • Properties of alcohols are different depending on their structure
     • Short alcoholshave low boiling points because the intermolecular forces are weak
     • Longer hydrocarbons behave like an alkane. They are less soluble on water and float due to their low density

4. Alcohol Reactions

   • Alcohol reacts with sodium to produce a Salt and hydrogen gas
     • Ethanol + Sodium = Sodium Ethoxide + Hydrogen
       • 2C3H5OH + 2Na = 2C2H5O-Na+ + H2
     • Alcohols, water and alkanes react differently with Sodium
       • In Alcohol, sodium sinks, doesn't melt and steadily gives of Hydrogen gas
       • There is no reaction between sodium and Alkane
       • In water sodium melts, fizzes and whizzes round on the surface, rapidly giving off hydrogen
   • Alcohols burn in air because of the presence of a hydrocarbon chain
     • When Ethanol burns in air
       • 2C2H5OH + 3O2 = 3H2O + 2CO2