Alkanes

• The reaction between alkanes and group 7 Elements is called homolytic fission
• Hydrocarbons are compounds containing only hydrogens and carbons
• Catenation is the ability for carbon to form chains and rings
• A homologous series are a family of compounds with the same functional group which differ in formula by CH2 from the next member
• A homologous series will

  • have the same general formula
  • have similar chemical properties
  • contain the same functional groups
• A functional group is the atom or group of atoms responsible for the chemical behaviour of a molecule
• Each functional group has its own distinctive properties which means the properties of a compound is controlled by the functional groups it has
• Aromatic compounds are made up of chains of carbon atoms which may be straight or branched
• Alicyclic/ cyclic compounds are made up of closed rings of carbon atoms and form cyclo alkanes
• Aromatic compounds contain arene (benzene like) rings and often have distinctive smells which aren’t alway pleasant
• Saturated compounds contain only single covalent bonds between carbons. They have a maximum number of hydrogens
• Unsaturated compounds contain double or triple bonds between carbons atoms which can have more hydrogen atoms added to form additional C-H bonds. They don’t have the maximum number of hydrogens bonded to them
• Empirical formula is the simplest whole number ratio of atoms

  C5H12
• The molecular formula is the actual number of each type of atoms
• Structural formula is in minimal detail of how the functional groups and atoms are bonded together

  CH3CH2CH3
• Displayed formula shows all the atoms and bonds between them in a compound

  
• Skeletal formula shows the functional group but hydrocarbons shown as lines

  
• Writing the names for organic compounds goes in alphabetical order
• A structural isomer occurs when two or more compounds have the same molecular formula but different structural formulae
• Chain isomers are a type of structural isomer. They have a different arrangement of the carbon chain but the same molecular formula.
• The shorter the chain of the alkane the weaker the forces of attraction making them easier to boil
• Branching decreases the boiling point because it creates a smaller surface area but increases melting point
• Attractive forces between branched molecules are weaker because the branching prevents close contact with other molecules
• Alkanes are insoluble
• Fractions collected from fractional distillation need further refining to remove sulfur compounds
• Cracking a is the break down of long chain molecules to shorter molecules by heating with a catalyst
• Straight chain compunds burn less efficiently than branched or cyclic compounds because they have a lower number of bonds to react with oxygen
• The process of reforming convert straight chain alkanes into branched alkanes and cyclic compounds making them more efficient for burning
• Reforming straight chain alkanes converts them into branched or cyclic compounds through heating and with a platinum catalyst
• The greenhouse effect is the trapping of infared radiation in the earths atmosphere which warms the earth
• Alkanes burn to produce carbon dioxide and water
• Incomplete combustion of alkanes can give then products carbon solid and carbon monoxide
• In the presence of ultra violet light alkanes can react with group 7 elements in a substitution reaction. for example it can form chloroalkanes when reacting with chlorine
• Steps to a mechanism are

  • Initiation
  • propagation
  • termination
• Homolytic fission is the term used to describe the breaking of covalent bonds so that the bonding electrons are shared equally between the atoms involved
• Heterolytic fission is when both electrons are converted to one of the atoms involved leaving the remaining atom as an ion
• A free radical are molecular fragments or atoms with one unpaired electron and are highly reactive
• A substitution reaction Is where one atom or group of atoms replace another atoms or group of atoms
• Initiation step goes form 0 free radicals to 2 free radicals as a product
• Propagation has 2 parts and has 1 free radical reacting with 1 non free radicals to produce 1 non free radical and 1 free radical