organic chemistry

• Crude oil


  A mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
• Crude oil is a finite resource - cannot be replaced as it is used up
• Hydrocarbon


  A compound made up exclusively of hydrogen and carbon atoms
• Alkanes


  Saturated hydrocarbons of a general formula CnH2n+2
• Homologous series


  Series of compounds with same general formula, same functional groups and similar chemical properties
• Combustion of hydrocarbons


  1. Exothermic reaction

  2. Complete combustion produces carbon dioxide and water

  3. Incomplete combustion produces carbon or carbon monoxide and water
• Physical properties of alkanes

  • First few in series are gases, then change to liquids, then to solids
  • Boiling points and viscosity increase as molecules get bigger
  • Volatility and flammability decrease as molecules get bigger
  • Poor reactivity
• Fractional distillation of crude oil

  1. Crude oil is heated and vaporised

  2. Vapor rises up the fractionating column (tower)

  3. The column is hotter at the bottom and cooler at the top

  4. Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points

  5. Large molecules, high boiling points - collected at the bottom

  6. Small molecules, low boiling points - collected at the top

  7. This gives fractions, which can be used in various ways
• Cracking


  When large hydrocarbons are thermally broken down into smaller and useful molecules
• Type of reaction for cracking

  Thermal decomposition
• Conditions for cracking


  Reactant heated to vapor, passed over a hot catalyst (catalytic cracking) or heated to vapor, mixed with steam and heated to high temperatures (steam cracking)
• Products of cracking


  Alkanes and alkenes – used as polymers and starting materials for synthesis
• Alkene


  Unsaturated hydrocarbon. Contains a C=C bond. General formula for alkenes is: CnH2n
• Test for alkenes


  Add bromine water. Colour change occurs from orange to colourless
• Combustion of alkenes


  • They burn with smoky flames due to incomplete combustion
• Addition reactions of alkenes

  1. Addition atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond

  2. With hydrogen - hydrogenation; requires a higher temperature and a nickel catalyst

  3. With steam - hydration; requires high temperature, pressure, and concentrated phosphoric acid (H3PO4) as a catalyst

  4. With Br2/Cl2/I2 - addition of halogens
• Alcohol


  An organic compound that contains an -OH functional group
• Characteristics of methanol, ethanol, propanol and butanol

  • Dissolve in water to form a neutral solution
  • React with sodium to form hydrogen
  • Burn in oxygen
  • React with carboxylic acids in presence of acid catalyst to form esters
• Oxidation of the alcohols


  Leads to carboxylic acids
• Uses of alcohols


  • Fuels
  • Solvents
  • Drinks
• Fermentation of glucose


  1. 30 degrees Celsius, aqueous solution of the glucose, absence of air, yeast added

  2. C6H12O6 → 2 CH3CH2OH + 2 CO2
• Carboxylic acids


  Organic compounds that contain a COOH functional group
• Characteristics of carboxylic acids

  • Dissolve in water to form an acidic solution (contains H+ ions)
  • React with metal carbonates to produce carbon dioxide and a salt
• Fermentation of glucose


  1. 30 degrees Celsius

  2. Aqueous solution of the glucose

  3. Absence of air

  4. Yeast added
• Characteristics of carboxylic acids

  • Dissolve in water to form an acidic solution (contains H+ ions)
  • React with metal carbonates to form carbon dioxide
  • React with alcohols with an acid catalyst to produce esters
  • React with metals to give off hydrogen gas
• Carboxylic acid


  It is a weak acid
• Ester


  An organic compound containing a -COO- functional group, formed from carboxylic acid and alcohol in the presence of a sulfuric acid catalyst
• Esters have a fruity smell
• Polymer


  A long chain molecule which is made by lots of smaller molecules joining together
• How molecules containing C=C bond form polymers


  1. C=C bonds open up and many smaller molecules (monomers) join together to form a chain (a polymer)

  2. No other products are made

  3. It is called an "addition polymerisation" reaction
• Addition polymers


  • Polyethene - plastic bags
  • (Poly)tetrafluoroethene (PTFE) - teflon surfaces, for use in non-stick kitchenware
  • (Poly)chloroethene (polyvinylchloride, PVC) - water pipes
• Repeating unit of a polymer

  • It is a smallest structure which, upon numerous translations, yields the structure of the polymer
  • In addition polymers: to draw it, take a monomer, change C=C to C-C and show additional single bonds extending away from these carbons
• Condensation polymer


  • It is a polymer made in condensation polymerisation
  • In this reaction, many molecules join together; the polymer is formed, but also a small molecule is released, e.g. H2O, HCl
• Main groups of condensation polymers

  • Polyesters, e.g. terylene
  • Polyamides, e.g. Nylon
• Amide bond


  • An amide bond is similar to the ester bond, with O replaced by N, e.g. (C=O)-NH2
  • Just like an ester, it contains the C=O group
• Amino acid


  It is an organic compound that contains both a carboxylic acid functionality (COOH) and an amine functional group (-NH2)
• How amino acids make proteins

  1. By numerous condensation polymerisation reactions; proteins are polymers made of amino acids (monomers)

  2. Polypeptides are also made by condensation polymerisation of amino acids, but are shorter than proteins. One could think about proteins as a product of many polypeptide chains bonded together
• Carbohydrates


  • They are organic molecules made of C,H, and O. They are biologically relevant, e.g. starch and cellulose
  • Both of these are polymers made of glucose (other carbohydrate) monomers. Their structures differ in the way the glucose molecules are joined together
• DNA (deoxyribonucleic acid)


  • It is a material that makes up chromosomes - cell structures that store genetic information
  • DNA is made of two polymer chains that are held together in a double helix
  • Each polymer chain can be made from 4 different monomers - nucleotides