chemistry organic

• hydrocarbons


  any compound that is formed from carbon and hydrogen atoms only
• alkanes


  1. simplest type of hydrocarbons

  2. general formula CnH2n+2

  3. alkanes are homologous series - all react in the same way

  4. alkanes are saturated compounds
• the first 4 alkanes are

  methene CH4

  ethene C2H6

  propane C3H8

  butane C4H10
• hydrocarbons properties

  the shorter the carbon chain, the more runny the hydrocarbon is, less viscous it is , more volatile , lower boiling points and more flammable
• complete combustion

  happens when theres plenty of oxygen

  the only wate products are carbon dioxide and water

  
  

  hydrocarbon + water --> carbon dioxide + water
• crude oil


  crude oil is a fossil fuel that is formed from the remains of plants and animals mainly plankton. over millions of years of high pressure and high temperatures.

  finite resource.
• fractional distillation


  separation of a liquid mixture into fractions differing in boiling point (and hence chemical composition) by means of distillation, typically using a fractionating column.

  
  

  long chain hydrocarbons at the bottom due to higher boiling points and they drain out at the start and shorter chain hydrocarbons at the top

  
• crude oil uses


  Oil provides the fuel for most modern transport

  = cad, train, planes etc

  
  

  The petrochemical industry uses some of the hydrocarbons from crude oil as a feedstock to make new compounds for use in things like polymers, solvents, lubricants, and detergents

  
  

  All products from crude oil are organic compounds (compounds w/ carbon atoms)

  = as carbon atoms can bond together to form different groups called homologous series

  = these groups contain similar compounds with many properties in common
• cracking


  short chain hydrocarbons are very useful as they are flammable and make good fuel so in high demand.

  long chain hydrocarbons are gloopy and not useful so cracking can turn long chain hydrocarbons into short chain hydrocarbons

  cracking can also turn alkanes into alkenes.
• methods of cracking


  cracking is a thermal decomposition method

  1. heat long chain hydrocarbons to vaporise them

  2. the vapour is then passed over a hot powdered aluminium oxide catalyst

  3. the long chain molecules split apart on the surface of the specks of catalyst - this is catalytic cracking

  4, you can also vaporise them, mix them with steam and then heat them too high temperatures, this is steam cracking
• alkenes


  alkenes have a c=c double bond. this means alkenes have two fewer hydrocarbons compared to alkanes containing the same number of carbon atoms. this makes alkenes unsaturated.

  the double bond can open up making alkenes more reactive than alkanes

  general formula = CnH2n
• first 4 alkenes


  ethene C2H4

  propene C3H6

  butene C4H8

  pentene C5H10
• incomplete combustion


  when there is not enough oxygen in the air for complete combustion , incomplete combustion happens.

  carbon dioxide and water are still produced but you also get carbon and carbon monoxide which is a poisonous gas.

  
  

  alkene + oxygen --> carbon + carbo monoxide + carbon dioxide + water

  
  

  incomplete combustion results in a yellow smoky flame and less energy released.
• reactions of alkenes


  1. via addition reactions - double bond opens up to leave a single bond and a new atom is added to each carbon

  2. addition of hydrogen is called hydrogenation - hydrogen reacts with the carbon to create the equivalent, saturated, alkane.

  3. steam can react with alkenes to form alcohols

  4. halogens can react with alkenes in addition reactions.
• polymers


  polymers are long molecules formed when lots of small molecules called monomers join together.

  this reaction is called polymerisation- needs high pressure and a catalyst.

  
  

  plastics are made from polymers. they are usually carbon based and their monomers are often alkenes.
• addition polymers


  lots of unsaturated monomer molecules - alkenes - can open up their double bond and join together to form polymer chains. this is addition polymerisation.
• alcohols


  homologous series

  functional group is -OH

  general formula is CnH2n+1+OH
• first 4 alcohols


  methanol CH3OH

  ethanol C2H5OH

  propanol C3H7OH

  butanol C4H9OH
• alcohol properties


  flammable

  undergo complete combustion

  soluble in water

  can react with sodium to make hydrogen

  can be oxidised to create carboxylic acids
• alcohol uses


  used as solvents and fuels
• ethanol


  ethanol is usually used by fermentation

  fermentation uses an enzyme in yeast to convert sugars into ethanol and happens fastest at 37 degrees in a sightly acidic solution and under anaerobic solutions.

  sugar--> ethanol + carbon dioxide
• carboxylic acids


  homologous series

  functional group is -COOH
• first 4 carboxylic acids

  Methanoic acid HCOOH

  Ethanoic acid CH3COOH

  Propanoic acid C2H5COOH

  Butanoic acid C3H7COOH
• carboxylic acid reactions


  they react like any other acid

  the react with carbonates to produce salt, water and carbon dioxide. the salts formed in these reactions end in anoate.

  
  

  ethanoic acid + sodium carbonate --> sodium ethanoate + water + carbon dioxide

  
  

  they can dissolve in water, when they dissolve they ionise and release H+ ions.
• esters


  have the functional -COO-

  esters are formed from an alcohol and carboxylic acid

  an acid catalyst is usually used

  
  

  alchol + carboxylic acid --> ester + water

  ethanol + ethanoic acid --> ethyl ethanoate + water
• condensation polymers


  polymers containing different functional groups

  monomers form bonds

  e.g. polyester
• amino acids


  amino acids contain two different functional groups - an amino group NH2 and an acidic carboxylic group COOH
• proteins


  amino acids can form polymers known as polypeptides via condensation polymerisation

  one or more polypeptides are known as proteins