Organic chemistry

• functional group


  groups of atoms responsible for the characteristic reactions of a particular compound
• naming organic compounds


  3 steps:

  1. Find the suffix (dictated by its functional group)
  2. find the prefix (dictated by the number of carbon atoms)
  3. find the position of the functional group
• structural isomers


  molecules that have the same molecular formula but have a different arrangement of the atoms in space
• homologous series


  a series of compounds with the same functional group
• characteristics of a homologous series

  all members of the series can be presented by the same general formula

  • consecutive members of the series differ by CH2
  • they have similar chemical properties because they have the same functional group
  • their physical properties change in a predictable way
• Alkanes

  • end with 'ane'
  • are saturated hydrocarbons that only have single carbon-carbon bonds
  • the carbons are attached to hydrogen with single bonds
  • general formula: CnH2n+2
  • generally unreactive
  • undergo combustion and substitution reaction
• Petroleum (crude oil) is a complex mixture of hydrocarbons that also contains natural gas

  • it is a thick, sticky, black liquid found under porous rock (under the ground and sea)
  • the fractions in petroleum are separated from each other in a process called fractional distillation
• the molecules in each fraction have similar properties and boiling points, which depend on the number of carbon atoms in the chain

  • the boiling point and viscosity of each fraction increase a the carbon chain gets longer
• viscosity


  the viscosity of a liquid is a description of its resistance to flow or refers to the ease of flow of a liquid.

  • a viscous liquid like honey flows much more slowly than a non-viscous liquid like ethanol
  • high-viscosity liquids are thick and flow less easily. With an increase in carbon atom count, the hydrocarbon molecules' attraction to one another also increases, making the liquid more viscous as the hydrocarbon chain lengthens.
  • the liquid flows less easily with increasing molecular mass
• fractional distillation

  • carried out in a fractioning column, which is hot at the bottom and cools at the top. Crude oil enters the fractioning column and is heated, so vapors rise.
  • vapors of hydrocarbons with very high b.p. will immediately turn into liquid and are tapped off at the bottom
  • vapors of hydrocarbons with low b.p. will rise up the column and condense at the top to be tapped off
• the different fractions condense at different heights according to their b.p. and are tapped off as liquids

  • the fractions containing smaller hydrocarbons are collected at the top of the fractioning column as gases
  • the fractions containing bigger hydrocarbons are collected at the lower sections of the fractioning column
• Mnemonic

  • Refrigerated: refinery gases
  • Ganglia: gasoline/petrol
  • Never: Naptha
  • Knew: kerosense
  • Dogs: diesel
  • Feed: fuel oil
  • Lions: lubricating oil
  • Butter: bitumen
• Viscosity


  The liquid flows less easily with increasing molecular mass
• As carbon chain length increases

  The color of the liquid gets darker as it gets thicker and more viscous
• As the molecules get larger


  The intermolecular attraction becomes greater. More heat is needed to separate the molecules. With increasing molecular size there is an increase in boiling point
• Volatility


  The tendency of a substance to vaporize
• With increasing molecular size

  Hydrocarbon liquids become less volatile because the attraction between the molecules increases
• uses of fractions

  • refinery gas: heating and cooking
  • gasoline: fuel for cars (petrol)
  • naphtha: raw product for producing chemicals
  • kerosene: for making jet fuel (paraffin)
  • diesel: fuel for diesel engines (gas oil)
  • fuel oil: fuel for ships and for home heating
  • lubricating oil: for lubricants, polishes, and waxes
  • bitumen: for surfacing roads
• substitution reaction


  one atom (or a groip of atoms) is replaced by another atom (or a group of atoms)

  • alkanes undergo a substitution reaction with halogens in the presence of ultraviolet light radiation (sunlight is a source of UV radiation), this reaction is called a photochemical reaction.
  • the UV light provides the activation energy, Ea, for the reaction. A hydrogen atom is replaced with the halogen atom, and more than one hydrogen atom can be substituted depending on the amount of ultraviolet radiation present
• In the presence of ultraviolet (UV) radiation, methane reacts with chlorine to form chloromethane and hydrogen chloride

  • chloromethane: CH4 + Cl2 ---> HCl + CH3Cl
  • dichloromethane: CH2Cl + Cl2 ---> HCl + CH2Cl2

  
• complete combustion of an alkene

  gives carbon dioxide and water

  • CH4 + 2O2 ---> CO2 + 2H2O
• incomplete combustion of an alkene

  gives carbon monoxide and water

  • 2CH4 + 3O2 ---> 2CO + 4H2O
• Alkenes

  • end in 'ene'
  • hydrocarbons
  • general formula: CnH2n
  • contain carbon double bonds (C=C)
  • functional group: carbon-carbon double bond (C=C)
  • undergo addition reactions and are therefore called unsaturated hydrocarbons
• Manufacture of alkenes

  • alkenes are made by cracking alkanes
  • large alkane molecules obtained by fractional distillation of petroleum, are passed over a heated catalyst (silicon IV oxide & aluminium oxide)
  • larger alkanes are broken down into simpler alkanes, alkenes and possibly hydrogen
  • C10H22 ---> C8H18 + C2H4 (decane ---> octane + ethene)
  • C10H22 (g) ---> C7H14 (g) + C3H6 (g) + H2 (g) (Alkane ---> Alkene + Alkene + Hydrogen)
• addition reaction

  the C=C double bond in alkenes can be broken to "add" molecules onto the compound

  • alkenes can undergo addition reactions with bromine, hydrogen and steam
• aqueous bromine undergoes addition reactions with alkenes. As a result, the original brown color of aqueous bromine will turn colorless in the presence of alkenes.

  • each carbon atom of the double bond accepts a bromine atom, causing the bromine solution to lose its color

  
• Hydrogen reacts with alkenes to produce alkenes. These are hydrogenation reactions and occur at

  • 150 degrees
  • using a nickel catalyst
  • hydrogenation reactions are used to manufacture margarine from vegetable oils

  
• water can react with alkenes to make alcohols. This type of reaction is called hydration

  The conditions required from this reaction are:

  • temperature of around 300 degrees
  • pressure of 60-70 atm
  • concentrated phosphoric acid catalyst

  
• Addition polymerization

  • polymerization is the formation of long chain molecules called polymers from a large number of smaller monomer molecules
  • ex. polymers (polystyrene and PVC)
  • the monomers form repeat units, which are linked by covalent bonds
  • addition polymers are formed from monomers containing C=C bonds
• • the C=C bond of the monomer breaks and the monomer forms a single bond with an adjacent monomer
  • put the monomer name in brackets and add 'poly' in front of the monomer name

  
• to deduce the monomer from the polymer

  • identify the repeating unit in the polymer
  • change the single bond in the repeat until to a double bond in the monomer
  • remove the bond from each end of the repeat unit

  
• to draw the repeat unit

  • change the double bond to a single bond
  • add the group from monomer into the correct place
  • add a bond to each end of the repeat unit
  • add brackets
  • write a small "n" in the bottom right hand side
  • make sure the bonds extend outside the brackets
• Alcohols

  • ends with '-ol'
  • general formula: CnH2n+1OH
  • OH is the functional group
• Hydration of etheneadvantages


  1. No waste products

  2. Continuous production
• Hydration of ethenedisadvantages


  • Use of crude oil, which is non-renewable
  • Requires a lot of energy for high heat and pressures
• Fermentation


  1. Chemical breakdown of glucose by yeast (or other microorganisms)

  2. Producing carbon dioxide and ethanol

  3. Reaction catalysed by yeast enzymes
• Fermentation reaction


  C6H12O6 → 2CO2 + 2C2H5OH
• Fermentationadvantages


  • Renewable (uses plants)
  • Uses less energy (lower temperature & pressure)
• Fermentationdisadvantages


  • Slow, batch process ie needing new batch once yeast die
  • Produces carbon dioxide as waste
• Ethanol properties & uses

  • ethanol burns with blue flame. Combustion of ethanol will produce carbon dioxide and water
  • C2H5OH + 3CO2 ---> 2CO2 + 3H2O

  It can be used:

  • as a fuel (ie combusted)
  • as a solvent I perfume and food industries
  • in some cultures in alcoholic drinks
  • to make otherorganic chemicals such as esters