Organic chem

• Organic Chemistry


  Chemistry of compounds which all contain carbon atoms and in general hydrogen atoms and sometimes oxygen, nitrogen, sulfur atoms
• Molecular formula


  Gives the number of atoms for each element present in the molecule. Gives information about the structure.
• Empirical formula


  Gives the simplest whole-number ratio of the atoms present in a compound.
• Structural formula


  Gives information about the structure and how the atoms are connected to each other.
• Displayed formula


  Shows all the bonds in the molecule as individual lines. Each line represents a shared pair of electrons (covalent bond).
• Hydrocarbons


  Molecules only made of carbon atoms and hydrogen atoms.
• Alkanes


  Hydrocarbons made of only carbon-carbon single bonds (C-C).
• Saturated compound


  Compound only has carbon-carbon single bonds.
• Alkenes


  Hydrocarbons which contain at least one carbon-carbon double bond (C=C).
• Unsaturated compounds


  Contain one or more carbon-carbon double or triple bonds.
• Homologous series


  A family of compounds with similar chemical properties because they have similar functional groups. Each member differs from the next by CH2.
• General formula


  An algebraic formula which gives the number of each atom in a molecule if there are n atoms of carbon for any member of a family of compounds.
• Isomers


  Molecules with the same molecular formula but different structures.
• Alkenes


  • Carbon atoms always make 4 covalent bonds and in alkenes there is a carbon-carbon double bond. The carbons in the double bond will also have single bonds to either an H or a C.
• Alkenes


  Unsaturated hydrocarbons because they are only made of carbon and hydrogen atoms and have at least one carbon-carbon (C=C) double bond.
• Isomers of but-2-ene (C4H8)

  • CH2=CHCH3

  CH2CHCH3

  CH2CH=CH2
• Alkanes


  • Saturated simple covalent molecules. The boiling points of alkanes increases as the number of carbon increases. This is because as the length of the alkane increases the intermolecular forces increase, so more energy is needed to break the intermolecular forces to separate the molecules.
• The first 4 alkanes are gases and the alkanes up to C16H34 are liquids. After that they start to be solids.
• Alkanes have similar properties as they only contain single carbon-carbon bonds and carbon-hydrogen bonds. These are strong covalent bonds and are hard to break and therefore alkanes don't react easily.
• Alkanes are less dense than water and stay on top of water. They are not very reactive.
• Hydration of ethene to make ethanol

  Ethene + Water -> Ethanol

  C2H4 + H2O -> CH3CH2OH

  Conditions: Temperature 300°C, Pressure 60-100 atm, Catalyst H3PO4
• Fermentation to make ethanol

  Glucose -> Ethanol + Carbon Dioxide

  Catalysed by enzymes in yeast (anaerobic respiration)
• Reversible reactions


  Reactions that can go in both the forward and reverse direction. At dynamic equilibrium, the forward and reverse reactions happen at the same rate, so there is no overall change in concentrations.
• The position of an equilibrium can be moved by changing external conditions like temperature, concentration and pressure.
• Crude oil


  A mixture of hydrocarbons which boil at different temperatures.
• The lower the number of carbon atoms in a hydrocarbon, the lower its boiling point and the more volatile it is.
• Fractions


  Groups of hydrocarbons with similar numbers of carbons and similar boiling points.
• Cracking in the laboratory

  Place mineral wool in bottom of boiling tube

  2. Add liquid paraffin

  3. Add catalyst (porous pot fragments)

  4. Heat catalyst to dull red heat

  5. Vapourise some of the liquid paraffin

  6. Collect gas and test with bromine water (turns colourless, indicating alkene)
• Reversible reactions under closed systems

  1. Reach dynamic equilibrium

  2. Forward reaction and reverse reaction happen at the same rate

  3. No overall change in concentration of reactants or products

  4. Reactions still happening
• Homologous series


  • Similar/same chemical properties
  • Same functional group (alcohol - OH, alkene c=c)
  • Show trends in physical property
  • Each successive member differs by CH2
  • Same general formula
• Alkenes have lower boiling points than alkanes due to their polar nature caused by the presence of the double bond.
• Alkenes are unsaturated hydrocarbons that contain at least one carbon-to-carbon double bond.
• Exothermic reaction


  1. Reactants are at a higher energy level than the products

  2. The difference in height between the two levels is the energy that is released

  3. The system has less energy after the reaction than it had before

  4. The surroundings have now more energy
• Endothermic reaction


  1. The products are at a higher energy level than the reactants

  2. The difference in height between the two levels is the energy that is absorbed

  3. The system has more energy after the reaction than it had before

  4. The surroundings have now less energy
• Before cars became common, there was not a great demand for fuels
• Most of the fuels available from crude oil were used in lamps and for steam engines
• When the internal combustion engine was invented, it needed a particular fraction of oil-the one we call petrol
• As cars became more common, the oil producers could not provide enough petrol (containing small hydrocarbon molecules) with extracting more crude of overall because crude oil contains lots of large hydrocarbon molecules
• Fractions of crude oil

  • gases
  • Petrol (gasoline)
  • kerosene
  • diesel
  • fuel oil & bitumen
• There is a big demand for small molecules like petrol and gases