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Unit 2

Unit 2. The World of Carbon. Menu. Fuels Nomenclature Reactions of Carbon Compounds Polymers Natural Products. Fuels. Crude oil. Crude oil is a source of many fuels.

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Unit 2

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  1. Unit 2 The World of Carbon

  2. Menu • Fuels • Nomenclature • Reactions of Carbon Compounds • Polymers • Natural Products

  3. Fuels

  4. Crude oil • Crude oil is a source of many fuels. • It is also the principal feedstock for the manufacture of petroleum-based consumer products because these are compounds of carbon.

  5. Petrol • Petrol can be produced by the reforming of naphtha. • Reforming alters the arrangement of atoms in molecules without necessarily changing the number of carbon atoms per molecule.

  6. Aromatic hydrocarbon Branched-chain hydrocarbon Cycloalkane • As a result of the reforming process, petrol contains branched-chain alkanes, cycloalkanes and aromatic hydrocarbons as well as straight-chain alkanes.

  7. Any petrol is a blend of hydrocarbons which boil at different temperatures. A winter blend of petrol is different from a summer blend. In winter butane is added to petrol so that it will catch fire more easily.

  8. Engines • In a petrol engine, the petrol-air mixture is ignited by a spark. • ‘Knocking’ is caused by auto-ignition. • Auto-ignition is when the petrol-air mix ignites too soon due to the heat from the engine. This makes the engine perform badly. • Knocking is when the engine shakes and shudders.

  9. The tendency of alkanes to auto-ignite used to be reduced by the addition of lead compounds. Unfortunately the lead compounds cause serious environmental problems.

  10. Unleaded petrol uses components which have a high degree of molecular branching and/or aromatics and/or cycloalkanes to improve the efficiency of burning.

  11. Alternative fuels • Fossil fuels are going to run out in the future. • Fuels used produce carbon dioxide, which increases the “greenhouse effect”. • We need other fuels which are renewable and non-polluting.

  12. Sugar cane is a renewable source of ethanol for mixing with petrol. Some biological materials,(i.e. manure and straw) under anaerobic conditions, ferment to produce methane (biogas). Methanol is an alternative fuel to petrol, but it has certain disadvantages, as well as advantages.

  13. Almost complete combustion No carcinogens Cheaper than petrol Less explosive than petrol Little modification to car engine Difficult to mix with petrol Very corrosive Toxic Larger fuel tanks needed. Methanol

  14. Hydrogen could well be the fuel of the future. If water can be electrolysed, using a renewable energy source, such as solar power, hydrogen will be obtained. The hydrogen will burn, producing water, and so will be pollution-free. The problem with hydrogen is storing the gas in large enough quantities.

  15. Fuels •  Click to repeat Fuels • Click to return to the Menu • Click to End

  16. Nomenclature & Structural formula

  17. Nomenclature • Nomenclature means the way chemical compounds are given names. • These names are produced by a special system.

  18. Naming organic compounds • All organic compounds belong to “families” called homologous series. • A homologous series is a set of compounds with the same general formula, similar chemical properties and graded physical properties.

  19. Most homologous series have a special functional group. A functional group is a reactive group of atoms which are attached to the carbon chain. The functional group is the part of the molecule where most reactions take place.

  20. C C C C O H Functional Groups

  21. C OH NH2 O C H C O O Functional Groups

  22. The first part of the compound’s name is decided by the number of carbon atoms in the molecule. The second part of the name is decided by the homologous series to which the compound belongs.

  23. 2nd Part of Name

  24. 2nd Part of Name

  25. This method works well for straight-chain hydrocarbons. Here is an example: hexane H H H H H H H C C C C C C H H H HH H H

  26. We have to add rules to help deal with branched chains. H H H H CH3 H H C C C C C C H H H CH3 H CH3 H

  27. First draw out the full structure. H H H H CH3 H H C C C C C C H H H CH3 H CH3 H

  28. Number the atoms in the longest continuous carbon chain. Start at the end nearer most groups. H H H H CH3 H H C C C C C C H H H CH3 H CH3 H 6 5 4 3 2 1

  29. This now gives us the basic name – in this case hexane. H H H H CH3 H H C C C C C C H H H CH3 H CH3 H 6 5 4 3 2 1

  30. You must now identify any side chains. -CH3 is methyl -CH2CH3 is ethyl

  31. Now identify and count the number and type of side chain. di - shows 2 tri – shows 3 tetra – shows 4 Label the carbon atom(s) they join

  32. This now gives us the full name: 2,2,4 trimethylhexane. H H H H CH3 H H C C C C C C H H H CH3 H CH3 H 6 5 4 3 2 1

  33. Naming other homologous series works in the same way. With those we start numbering at the end nearer the functional group e.g. this alkene: H H H H CH3 H H C C C C C C H H C2H5 CH3 H

  34. Number the atoms in the longest carbon chain. H H H H CH3 H H C C C C C C H H C2H5 CH3 H 1 2 3 4 5 6

  35. This now gives us the basic name – in this case hex-2-ene. H H H H CH3 H H C C C C C C H H C2H5 CH3 H 1 2 3 4 5 6

  36. Identifying the side chains gives us the full name: 5,5 dimethy 4 ethyl hex-2-ene. H H H H CH3 H H C C C C C C H H C2H5 CH3 H 1 2 3 4 5 6

  37. We can use the same principles with cyclic hydrocarbons. H H C H H C C H H C C H H H CH3

  38. 1 methyl cyclopentane H H C H H C C H H C C H H H CH3 3 2 4 1 5

  39. H H H H H C C C C H butane H H H H H H H H C C C H H H H C H H 2 methyl propane Isomers • Isomers are compounds with the same molecular formula but different structural formulae • For example C4H10

  40. Alcohols • The alcohols form another homologous series – called the alkanols. • We can recognise the alkanols because they contain an OH group. • They are given names as if they are substituted alkanes.

  41. 3 methyl pentan-2-ol H H CH3 H H H C C C C C H H H H OH H 5 4 3 2 1

  42. Aldehydes • The aldehydes form another homologous series – called the alkanals. • We can recognise the alkanals because they contain a carbonyl group at the end of the carbon chain. • They are named as if they are substituted alkanes.

  43. 3,4 dimethyl pentanal We don’t need to number the carbonyl group because it must be on the first carbon. H H CH3 H H H C C C C C O H CH3 H H 5 4 3 2 1

  44. Ketones • The ketones form another homologous series – called the alkanones. • We can recognise the alkanones because they contain a carbonyl group in the middle of the carbon chain. • They are named as if they are substituted alkanes.

  45. 3,3 dimethyl pentan-2-one H H CH3 H H C C C C C H H H CH3 O H 5 4 3 2 1

  46. Alkanoic acids • The alkanoic acids form another homologous series. • Carboxylic acids are used in a variety of ways.

  47. C OH O Alkanoic acids • We can recognise the alkanoic acids because they contain a COOH group.

  48. We can name the alkanoic acids using the principles we have used before. H H CH3 H H H C C C C C H H H H H C OH O

  49. H H CH3 H H H C C C C C H H H H H 6 5 4 3 2 1 C OH O • 4 methyl hexanoic acid • We don’t need to number the acid group because it must be on the first carbon.

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