Introductiontoorganicchemistry 090518040648 Phpapp02


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Introductiontoorganicchemistry 090518040648 Phpapp02

  1. 1. Introduction to Organic Chemistry
  2. 2. Contents <ul><li>Nomenclature and Isomerism </li></ul><ul><li>Petroleum and Alkanes </li></ul><ul><li>Alkenes and Epoxyethane </li></ul><ul><li>Haloalkanes </li></ul><ul><li>Alcohols </li></ul>
  3. 3. Nomenclature and Isomerism <ul><li>The study of the compound of carbon is called organic chemistry. </li></ul><ul><li>Groups of carbon compounds with the same functional group are called homologous series </li></ul><ul><li>Organic compounds are named according to their longest carbon chain. </li></ul>Hex- Pent- But- Pro- Eth- Meth- Prefix 6 5 4 3 2 1 Number of C atoms
  4. 4. 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
  5. 5. Isomerisation <ul><li>Both of the following have four carbon atoms and ten hydrogen atoms they are called isomers </li></ul>Butane 2-Methyl propane <ul><li>The number 2 indicates that the methyl group is attached to the second carbon. </li></ul><ul><li>Carbons are always number so that the lowest numbers appear in the name. </li></ul><ul><li>This type of isomerism is called structural isomerism </li></ul><ul><li>Positional isomers have functional groups at different positions along the chain </li></ul><ul><li>Functional group isomers have different functional groups but have the same molecular formulae, such as acids and esters </li></ul>CH 3 –CH 2 –CH 2 –CH 3 CH 3 –CH –CH 3 CH 3
  6. 6. Petroleum and Alkanes <ul><li>Petroleum </li></ul><ul><li>Combustion </li></ul><ul><li>Pollution </li></ul>
  7. 7. Petroleum <ul><li>Petroleum is another name for crude oil, it is a mixture of hydrocarbons. </li></ul><ul><li>The hydrocarbons in crude oil all have different boiling points, this property allows them to be separated by a process call fractional distillation. </li></ul><ul><li>Fractional distillation produces more long chain hydrocarbons than the market requires. They are made into shorter more useful molecules by a process called cracking. </li></ul><ul><li>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. </li></ul><ul><li>Zeolite catalysts can be used to lower the temperature of the cracking process. It proceeds via ionic intermediates. </li></ul>
  8. 8. Combustion <ul><li>In excess oxygen alkanes burn according to the following equation: </li></ul><ul><li>C n H 2n+2 +(1.5n+0.5)O 2  nCO 2 +(n+1)H 2 O </li></ul><ul><li>This is called complete combustion, however if there is in sufficient oxygen present incomplete combustion can occur. </li></ul><ul><li>C n H 2n+2 +(n+0.5)O 2  nCO +(n+1)H 2 O </li></ul><ul><li>With even less oxygen soot is formed. </li></ul>
  9. 9. Pollution <ul><li>Many pollutants are formed by the combustion of fossil fuels. These include soot and carbon monoxide formed by the incomplete combustion of hydrocarbons. </li></ul><ul><li>Besides making every thing look dirty carbon particulates in the atmosphere cause breathing problems in those who are susceptible. </li></ul><ul><li>Carbon monoxide interferes with the blood’s ability to carry oxygen and in severe case can lead to death. </li></ul><ul><li>Other harmful gases include: </li></ul><ul><ul><li>sulphur dioxide which is formed by the oxidation of impurities in fossil fuels </li></ul></ul><ul><ul><li>and nitrogen oxides which are formed atmospheric nitrogen is oxidised during the combustion process. </li></ul></ul><ul><li>Both of these species react with rain water to form acid rain. </li></ul>
  10. 10. Alkenes and Epoxyethane <ul><li>Alkenes are unsaturated. This means that they do not have the maximum possible number of hydrogen atoms. </li></ul><ul><li>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. </li></ul><ul><li>Because of the weaker second bond alkenes are more reactive than alkanes. </li></ul><ul><li>There is no rotation around the double bond, this causes alkenes to have a planar shape. </li></ul>
  11. 11. 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
  12. 12. Epoxyethane <ul><li>Epoxyethane is produced from ethene and air or oxygen in the presence of a silver catalyst. </li></ul><ul><li>The 3-membered ring is strained and results in high reactivity. </li></ul><ul><li>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. </li></ul>O CH 2 CH 2
  13. 13. Haloalkanes <ul><li>Haloalkanes contain polar bonds. This is because the halogen is more electronegative than the carbon. </li></ul><ul><li>This results in the carbon atom being slightly positive and attractive to electron rich species. </li></ul><ul><li>Reactions resulting from this type of attraction are called nucleophilic substitution. </li></ul>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.
  14. 14. Elimination <ul><li>On heating bromoethane with a strong base dissolved in ethanol, hydrogen bromide is eliminated and ethene is formed: </li></ul><ul><li>CH 3 CH 2 Br CH 2 =CH 2 + HBr </li></ul><ul><li>KOH/ethanol </li></ul>
  15. 15. 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
  16. 16. Manufacture of Alcohols <ul><li>Alcohol for human consumption is produced by natural fermentation. Yeasts produce enzymes which catalyse the reaction called zymases. </li></ul><ul><li>Industrially it cheaper to form ethanol for solvent by the hydrolysis of ethene. </li></ul><ul><li>It is cheaper to obtain ethanol in this manner because it is produced in a continuous process </li></ul>
  17. 17. Reactions of Alcohols <ul><li>Oxidation of primary alcohols produces an aldehyde. </li></ul><ul><li>Aldehydes produce a silver mirror with Tollen’s reagent </li></ul><ul><li>Secondary and tertiary alcohols produce ketones upon oxidation these do not give a silver mirror with ketones. </li></ul><ul><li>Heating alcohols with sulphuric or phosphoric acid causes them to eliminate water and produce alkenes </li></ul>
  18. 18. Summary <ul><li>Nomenclature and Isomerism </li></ul><ul><ul><li>Naming of organic compounds is systematic it depends on chain length and functional groups it allows us to identify isomers </li></ul></ul><ul><li>Petroleum and Alkanes </li></ul><ul><ul><li>Most of our hydrocarbon come from crude oil, they are used extensively for fuel. But this can cause environmental problems </li></ul></ul><ul><li>Alkenes and Epoxyethane </li></ul><ul><ul><li>Alkenes have a double bond which makes them much more reactive. They are a useful feedstock for the plastics industry </li></ul></ul><ul><li>Haloalkanes </li></ul><ul><ul><li>These molecules have polar bonds which results in them being susceptible to nucleophilic attack. </li></ul></ul><ul><li>Alcohols </li></ul><ul><ul><li>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. </li></ul></ul>