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Unit 2

Unit 2. Carbon compounds. Menu. To work through a topic click on the title. Fuels Nomenclature and structural formula Reactions of carbon compounds Plastics and synthetic fibres Natural products Click here to End. Fuels. Fuels.  A fuel is a chemical which burns, releasing energy.

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Unit 2

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  1. Unit 2 Carbon compounds

  2. Menu • To work through a topic click on the title. • Fuels • Nomenclature and structural formula • Reactions of carbon compounds • Plastics and synthetic fibres • Natural products • Click here to End.

  3. Fuels

  4. Fuels •  A fuel is a chemical which burns, releasing energy. • Combustion is another word for burning, the reaction of a substance with oxygen, in which energy is given out.

  5. Hydrocarbons • The chemical compounds which are found in oil and natural gas are mainly hydrocarbons. • A hydrocarbon is a compound which contains hydrogen and carbon only.

  6. Hydrocarbons burn in a plentiful supply of air to produce carbon dioxide and water. • The test for carbon dioxide is that it turns lime water milky.

  7. To pump Anhydrous copper sulphate (turns blue) Lime water (turns cloudy) Burning candle

  8. Incomplete Combustion • When fuels burn in a limited supply of air then incomplete combustion takes place and the poisonous gas, carbon monoxide (CO) is produced. • Increasing the amount of air used to burn fuel improves efficiency and decreases pollution.

  9. Other products of combustion • Fossil fuels contain sulphur which produces sulphur dioxide when the fuel is burned. • The oil industry tries to remove this sulphur from the fuels before selling them.

  10. High Voltage spark Air + - Nitrogen does not react well because of its strong bonds. If there is a high temperature the nitrogen and oxygen will combine to make nitrogen oxides. The experiment opposite shows how a high voltage spark, like one provided by the spark plug or lightning will do the same.

  11. High Voltage spark Air Brown gas + - Nitrogen does not react well because of its strong bonds. If there is a high temperature the nitrogen and oxygen will combine to make nitrogen oxides. The experiment opposite shows how a high voltage spark, like one provided by the spark plug or lightning will do the same.

  12. Atmospheric Pollution • The sulphur and nitrogen oxides produced can dissolve in water, making acid rain. • Unburnt hydrocarbons escaping from car exhausts can help cause the destruction of the ozone layer.

  13. Reducing Pollution • Air pollution caused by burning hydrocarbons can be reduced by: using a special exhaust system – a catalytic converter, in which metal catalysts (platinum or rhodium) will convert pollutants into harmless gases. altering the fuel to air ratio.

  14. Pollution • Soot particles produced by the incomplete combustion of diesel are harmful.

  15. Oil • Crude oil is a mixture of chemical compounds (mainly hydrocarbons) which can be to split it into fractions. • Oil can be separated into fractions by the process of fractional distillation.

  16. Oil • A fraction is a group of chemical compounds, all of which boil within the same temperature range.

  17. Fractional Distillation of Oil gases (gaseous fuel) petrol (gasoline) (petrol) naphtha (chemicals) paraffin (kerosine) Heated oil from furnace (aircraft fuel) diesel (fuel for lorries etc.) residue (wax, tar)

  18. Oil Fractions

  19. Viscosity is a measure of the thickness of a liquid. • Flammability is a measure of easily the liquid catches fire.

  20. As the boiling point of a fraction increases then: • it will not evaporate as easily. • it will be less flammable • it will be more viscous (thicker).

  21. Moving through the fractions from gases to the residue • The molecules present in the fraction are longer and heavier • They will find it more difficult to become a gas i.e. they will be less easy to evaporate.

  22. Moving up the fractions from gases to the residue • Since combustion involves the reaction of gas molecules with oxygen flammability will decrease. • Increased molecular lengths mean that molecules become more "tangled up", so the liquid will become thicker (more viscous).

  23. Fuels Click here to repeat Fuels Click here to return to the Menu Click here to End.

  24. Nomenclature & Structural formula

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

  26. Naming hydrocarbons • All hydrocarbons belong to “families” called homologous series. • A homologous series is a set of compounds with the same general formula and similar chemical properties.

  27. The other part of the name tells us how many carbon atoms are present.

  28. This method works well for straight-chain hydrocarbons like hexane. H H H H H H H C C C C C C H H H HH H H

  29. 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

  30. 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

  31. Number the atoms in the longest continuous carbon chain. Start at the end nearest 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

  32. 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

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

  34. 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

  35. 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

  36. Naming alkenes works in the same way, except we start numbering at the end nearer the double bond. H H H H CH3 H H C C C C C C H H C2H5 CH3 H

  37. 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

  38. 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

  39. 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

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

  41. 1 methyl cyclopentane H H C H H C C H H C C H H H CH3 3 2 4 1 5

  42. 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

  43. Alkanols • The alkanols form another homologous series. • We can recognise the alkanols because they contain an OH group.

  44. We can name the alkanols using the principles we have used before. H H CH3 H H H C C C C C H H H H OH H

  45. 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

  46. C OH O Alkanoic acids • The alkanoic acids form another homologous series. • We can recognise the alkanoic acids because they contain a COOH group.

  47. 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

  48. 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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