organic chemistry

• hydrocarbons consist of (only) hydrogen and carbon
• crude oil

  finite resource found in earth's crust

  it is the remains of organisms that lived and died millions of years ago (mostly plankton) which was buried under mud

  it is a complex mixture of hydrocarbons

  the carbon atoms are joined together in chains and rings

  
• crude oil is an important source of:

  • fuels (petrol, diesel, kerosene, heavy fuel oil and liquified petroleum gases)
  • feedstock for the petrochemical industry

  feedstock: raw material, used to provide reactants in an industrial reaction

  petrochemical: substance made from crude oil using chemical reactions

  > eg: ethene is produced from crude oil

  used as feedstock to make poly(ethene), a polymer

  other useful products of crude oil:

  • lubricant
  • solvents
  • detergents
• homologous series: a "family" of organic compounds that have the same functional group, and similar chemical properties
• like all homologous series, the alkanes:

  • have the same general formula
  • differ by a CH2 molecular formula
  • show gradual variation in physical properties (ie: boiling points)
  • have similar chemical properties
• formula for alkanes:

  CnH2n+2

  where n = the number of carbon atoms
• the alkanes go in the order:

  1. methane (CH4)
  2. ethane (C2H6)
  3. propane (C3H8)
  4. butane (C4H10)

  to remember: Monkeys Eat Peanut Butter

  from now on the first part is based off of shape names (relative to the number of carbons)

  5. pentane (C5H12) - pentagon

  6. hexane (C6H14) - hexagon

  7. heptane (C7H16) - heptagon

  8. octane (C8H18) - octagon

  9. nonane (C9H20) - nonagon

  10. decane (C10H22) - decagon
• the alkanes are saturated hydrocarbons because

  • compounds containing hydrogen and carbon only
  • carbon atoms are joined by C-C singe bonds
• fractional distillation is used to seperate crude oils into simpler, more useful mixtures

  this method can be used because different hydrocarbons have different boiling points
• hydrocarbons are made up of multiple differnt length hydrocarbons, and fractional distillation is just seperating them
• the liquid is heated until boiling

  the components vaporize at their differnt boiling points (lower boiling point vaporizes first)

  the column has a heating gradient: hot at bottom, cool at top

  the vapours condense and are led out of the column at different heights
• small hydrocarbons have weaker intermolecular forces, so they have low boiling points

  they don't condense, but leave the column as gases

  long hydrocarbons have stronger intermolecular forces, condense, and leave the column as hot bitumen
• small hydrocarbons

  • low boiling points
  • very volatile
  • flows easily, not viscous
  • ignites easily

  large hydrocarbons

  • high boiling points
  • not volatile
  • viscous
  • doesn't ignite easily
• Lazy - liquid petroleum gases (fuel for domestic heating and cooking)

  Penguins - petrol (fuel for cars)

  Keep - kerosene (fuel for aircraft)

  Drinking - diesel (fuel for some cars and trains)

  Hot - heavy fuel oil (fuel for ships and power stations)

  Beverages - bitumen (bitumen for roads and roofs)

  A) liquid petroleum gases

  B) petrol

  C) kerosene

  D) diesel

  E) heavy fuel oil

  F) bitumen

  
• hydrocarbons can undergo complete or incomplete combustion depending on how much oxygen is available
• complete combustion of a hydrocarbon fuel happens with sufficient oxygen supply (air)

  hydrogen and carbon react with oxygen (exothermic reaction):

  • carbon dioxide and water are produced
  • maximum amount of energy is released

  hydrocarbon + oxygen ---> carbon dioxide + water

  incomplete happens when there's not a sufficient supply of oxygen

  hydrogen and carbon react with oxygen to form water, & instead, carbon monoxide (exothermic reaction):

  • carbon moboxide and water are produced
  • less energy is given out (than complete combustion)

  hydrocarbon + oxygen ---> carbon monoxide + water
• cracking: larger, saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbons, some saturated and unsaturated

  • original starting hydrocarbons are alkanes
  • products are alkanes and alkenes

  alkenes are part of a different homologous series
• formula for alkenes

  CnH2n

  the names of alkenes are the exact same as alkanes, but just with "ene" ending not "ane"
• catalytic cracking

  uses temperatures about 550C

  uses a catalyst known as zeolite which contains aluminium oxide and silicon oxide

  steam cracking

  uses temperatures about 850C

  no catalyst
• cracking is important because:

  • helps match the supply of fractions with the demand for them
  • produces alkenes which are useful as feedstock for petrochemical industry
• very often fractional distillation produces more of the larger hydrocarbons (less demand) and less of the smaller hydrocarbons (high demand).

  since cracking turns larger hydrocarbons into shorter hydrocarbons, cracking helps improve supply and demand
• • alkanes are saturated: joined by a single C-C bond
  • alkenes are unsaturated: joined by a double C=C bond

  as a result alkenes are more reactive and can take part in reactions alkanes cannot

  eg: ethene molecules can react together to form poly(ethene) a polymer
• bromine water test

  alkenes

  will react with bromine water, and turn it from orange/brown to colourless

  this is a way to test for a double C=C bond in a molecule