Introductiontoorganicchemistry 090518040648 Phpapp02
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Introductiontoorganicchemistry 090518040648 Phpapp02 Introductiontoorganicchemistry 090518040648 Phpapp02 Presentation Transcript

  • Introduction to Organic Chemistry
  • Contents
    • Nomenclature and Isomerism
    • Petroleum and Alkanes
    • Alkenes and Epoxyethane
    • Haloalkanes
    • Alcohols
  • Nomenclature and Isomerism
    • The study of the compound of carbon is called organic chemistry.
    • Groups of carbon compounds with the same functional group are called homologous series
    • Organic compounds are named according to their longest carbon chain.
    Hex- Pent- But- Pro- Eth- Meth- Prefix 6 5 4 3 2 1 Number of C atoms
  • Nomenclature -oate Esters -oic C n H 2n CO 2 H Carboxylic Acids C=O -one Ketones -al Aldehyde – OH -ol C n H 2n+1 OH Alcohols – Cl or –Br chloro -, bromo- etc Haloalkanes C=C -ene C n H 2n Alkenes C –H -ane C n H 2n+2 Alkanes Functional group Name General Formula Homologous Series – C O H – C O O–C – C O OH
  • Isomerisation
    • Both of the following have four carbon atoms and ten hydrogen atoms they are called isomers
    Butane 2-Methyl propane
    • The number 2 indicates that the methyl group is attached to the second carbon.
    • Carbons are always number so that the lowest numbers appear in the name.
    • This type of isomerism is called structural isomerism
    • Positional isomers have functional groups at different positions along the chain
    • Functional group isomers have different functional groups but have the same molecular formulae, such as acids and esters
    CH 3 –CH 2 –CH 2 –CH 3 CH 3 –CH –CH 3 CH 3
  • Petroleum and Alkanes
    • Petroleum
    • Combustion
    • Pollution
  • Petroleum
    • Petroleum is another name for crude oil, it is a mixture of hydrocarbons.
    • The hydrocarbons in crude oil all have different boiling points, this property allows them to be separated by a process call fractional distillation.
    • Fractional distillation produces more long chain hydrocarbons than the market requires. They are made into shorter more useful molecules by a process called cracking.
    • Thermal cracking splits the bonds in the hydrocarbon by a free radical process this uses a lot of energy because of the high temperatures used.
    • Zeolite catalysts can be used to lower the temperature of the cracking process. It proceeds via ionic intermediates.
  • Combustion
    • In excess oxygen alkanes burn according to the following equation:
    • C n H 2n+2 +(1.5n+0.5)O 2  nCO 2 +(n+1)H 2 O
    • This is called complete combustion, however if there is in sufficient oxygen present incomplete combustion can occur.
    • C n H 2n+2 +(n+0.5)O 2  nCO +(n+1)H 2 O
    • With even less oxygen soot is formed.
  • Pollution
    • Many pollutants are formed by the combustion of fossil fuels. These include soot and carbon monoxide formed by the incomplete combustion of hydrocarbons.
    • Besides making every thing look dirty carbon particulates in the atmosphere cause breathing problems in those who are susceptible.
    • Carbon monoxide interferes with the blood’s ability to carry oxygen and in severe case can lead to death.
    • Other harmful gases include:
      • sulphur dioxide which is formed by the oxidation of impurities in fossil fuels
      • and nitrogen oxides which are formed atmospheric nitrogen is oxidised during the combustion process.
    • Both of these species react with rain water to form acid rain.
  • Alkenes and Epoxyethane
    • Alkenes are unsaturated. This means that they do not have the maximum possible number of hydrogen atoms.
    • The double bond in in alkenes is comprised of a covalent bond and a pi bond. The pi bond has electron density above and below the covalent bond and is weaker than a covalent bond.
    • Because of the weaker second bond alkenes are more reactive than alkanes.
    • There is no rotation around the double bond, this causes alkenes to have a planar shape.
  • Reactions of Alkenes +H 2 catalyst Heat & pressure +Br 2 +HCl +steam & catalyst n Catalyst & heat Remember in the presence of alkenes bromine water decolourises H H – C –C – H H Br Br – C –C – H Cl – C –C – H OH – C –C – alkane C=C
  • Epoxyethane
    • Epoxyethane is produced from ethene and air or oxygen in the presence of a silver catalyst.
    • The 3-membered ring is strained and results in high reactivity.
    • Epoxyethane is industrially important because it is hydrolysed to produce ethane-1,2 diol which is then used in the production of antifreeze and polyesters.
    O CH 2 CH 2
  • Haloalkanes
    • Haloalkanes contain polar bonds. This is because the halogen is more electronegative than the carbon.
    • This results in the carbon atom being slightly positive and attractive to electron rich species.
    • Reactions resulting from this type of attraction are called nucleophilic substitution.
    C Br : CN -  -  + The carbon atom of the CN - ion donates a pair of electrons to the haloalkane and the C –Br breaks with loss of a bromide ion. A new C –CN bond is formed.
  • Elimination
    • On heating bromoethane with a strong base dissolved in ethanol, hydrogen bromide is eliminated and ethene is formed:
    • CH 3 CH 2 Br CH 2 =CH 2 + HBr
    • KOH/ethanol
  • Alcohols Primary Secondary Tertiary Alcohols are classified according to the number of carbon atoms bonded to the carbon atom adjacent to the OH group. C OH C C C C OH H H C C OH H C C
  • Manufacture of Alcohols
    • Alcohol for human consumption is produced by natural fermentation. Yeasts produce enzymes which catalyse the reaction called zymases.
    • Industrially it cheaper to form ethanol for solvent by the hydrolysis of ethene.
    • It is cheaper to obtain ethanol in this manner because it is produced in a continuous process
  • Reactions of Alcohols
    • Oxidation of primary alcohols produces an aldehyde.
    • Aldehydes produce a silver mirror with Tollen’s reagent
    • Secondary and tertiary alcohols produce ketones upon oxidation these do not give a silver mirror with ketones.
    • Heating alcohols with sulphuric or phosphoric acid causes them to eliminate water and produce alkenes
  • Summary
    • Nomenclature and Isomerism
      • Naming of organic compounds is systematic it depends on chain length and functional groups it allows us to identify isomers
    • Petroleum and Alkanes
      • Most of our hydrocarbon come from crude oil, they are used extensively for fuel. But this can cause environmental problems
    • Alkenes and Epoxyethane
      • Alkenes have a double bond which makes them much more reactive. They are a useful feedstock for the plastics industry
    • Haloalkanes
      • These molecules have polar bonds which results in them being susceptible to nucleophilic attack.
    • Alcohols
      • The reaction of this series of compound depend on whether they are primary, secondary or tertiary. He primary being much more readily oxidised than the others.