Hydrocarbons

1
Hydrocarbons

• Keywords
• Alkanes uses, sources and reactions
• Alkenes uses, sources and reactions
• Alkynes uses, sources and reactions
• Types of reactions - A summary

2
Keywords

• These chemicals that we will be studying in this
  section are called hydrocarbons (they are
  composed of hydrogen and carbon).
• When discussing them we use a number of key
  words
• Saturated this term is used to describe an
  organic molecule who has no double or triple
  bonds
• Unsaturated this term is used to describe an
  organic molecule who has a double or triple bond
  between their carbons
• Polyunsaturated when an organic molecule has
  many double or triple bonds
• Melting/boiling point the temperature at which
  the specific molecule boils or melts. There is an
  important trend to do with this as the molecule
  gets bigger the melting and boiling points get
  higher (they are harder to melt)

3
Alkanes Uses and sources

• Alkanes are saturated organic molecules.
• Sources
• They can be made by adding hydrogen to
  unsaturated organic molecules
• They can be extracted from crude oil and natural
  gas
• Uses
• Alkanes are primarily used for fuels
• Methane
• Propane
• Octane
• They can also be used for lubricants (e.g.
  machine oil) and road surfaces (bitumen)

4
Alkanes - Reactions

• Combustion the burning of alkanes in oxygen to
  produce CO2 and H2O
• Cracking the snapping of long chain alkanes to
  produce an alkane and an alkene
• Substitution when a hydrogen is swapped with a
  different element normally a halogen

5
Alkenes Uses and sources

• Alkenes have a double bond present somewhere in
  their structure. This bond can be snapped open
  and other elements bonded to it. This makes them
  quite handy.
• Sources
• Alkenes can be created by cracking alkanes
• Uses
• Alkenes can be used for fuel
• They can be used as a building block for alkanes,
  alcohols and haloalkanes (see next page)
• They can be used to create various plastics

6
Alkenes - Reactions

• Combustion
• Addition when a double bond is broken and other
  components are added. There are a number of
  different types of addition reactions
• Hydrogenation the addition of hydrogen (with a
  Pt catalyst)
• Halogenation the addition of a halogen (e.g.
  Cl2)
• Hydrohalogenation the addition of a hydrogen
  halide (e.g. HCl)
• Hydration the addition of water
• Oxidation the use of MnO4- to add two OH
  groups
• In each of these cases what type of chemical
  would be produced?
• Polymerisation this is the linking together of
  many alkenes to create long chained organic
  molecules (plastics like polyethene)

7
Alkynes

• Alkynes have triple bonds and behave in a very
  similar way to alkenes except that they are more
  reactive. This means that there is no natural
  source of alkynes.
• Sources
• Ethyne is produced when you mix Calcium carbide
  (CaC2) with water
• Uses
• Ethyne (acetylene) is used in welding because it
  produces a lot of heat when burnt in pure oxygen
• Reactions
• Alkynes have exactly the same type of reactions
  as alkenes

8
Types of Reactions a summary

• Match the terms with the summaries below