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Topics 3abc – Alkanes, alkenes and ethanol Topics 5bc – natural oil and gas and synthetic polymers.

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Presentation on theme: "Topics 3abc – Alkanes, alkenes and ethanol Topics 5bc – natural oil and gas and synthetic polymers."— Presentation transcript:

1 Topics 3abc – Alkanes, alkenes and ethanol Topics 5bc – natural oil and gas and synthetic polymers

2 Crude oil (Petroleum) A mixture of hydrocarbons (chemicals which contain only hydrogen and carbon atoms)

3 Fractional distillation Separation of liquids with different boiling points

4 Fractional distillation The mixture can be split into simpler fractions by fractional distillation

5

6 Welcome to a new family

7 The alkanes

8 Methane (CH 4 )

9 Ethane (C 2 H 6 )

10 Propane (C 3 H 8 )

11 Butane (C 4 H 10 )

12 The alkanes Methane CH 4 EthaneC 2 H 6 PropaneC 3 H 8 ButaneC 4 H 10 PentaneC 5 H 12 HexaneC 6 H 14 OctaneC 8 H 18

13 The alkanes C n H 2n + 2 Methane CH 4 EthaneC 2 H 6 PropaneC 3 H 8 ButaneC 4 H 10 PentaneC 5 H 12 HexaneC 6 H 14 OctaneC 8 H 18 General formula Homologous group – similar chemical properties, structures and functional groups

14 The alkanes C n H 2n + 2 Methane CH 4 EthaneC 2 H 6 PropaneC 3 H 8 ButaneC 4 H 10 PentaneC 5 H 12 HexaneC 6 H 14 OctaneC 8 H 18 General formula Homologous group – similar chemical properties, structures and functional groups Generally unreactive, but burn exothermically. Longer chains burn less easily.

15 Structural formulae

16 Alkanes are saturated compounds No double bonds

17 Tetrahedral bonds In alkanes, the carbon bonds are tetrahedral

18 Chlorinated methane Methane can be chlorinated. Trichloromethane is commonly known as chloroform.

19 Isomers Same formula, but different structures We have slighty different physical properties (longer chains have higher boiling points)

20 Combustion

21 Hydrocarbons burn producing carbon dioxide and water CH 4 + 2O 2 CO 2 + 2H 2 O

22 Incomplete combustion When there is insufficient oxygen, carbon monoxide is also formed It reduces the blood’s oxygen carrying capability

23 Another family!

24 The alkenes C n H 2n Ethene C 2 H 4 Propene C 3 H 6 Butene C 4 H 8 Pentene C 5 H 10 Hexene C 6 H 12

25 The alkenes Unsaturated (contain a double bond) More reactive Can “add” atoms – addition reactions

26 Alkenes - equilateral The bonds on a double bonded carbon in an alkene point towards the corners of an equilateral triangle

27 Test for alkenes Decolourises bromine water etheneBromine (yellow/orange) Dibromoethane (colourless)

28 Alcohols - ethanol

29 Alcohols Methanol CH 3 OH Ethanol C 2 H 5 OH Propanol C 3 H 7 OH Butanol C 4 H 9 OH Pentanol C 5 H 11 OH Hexanol C 6 H 13 OH

30 Alcohols Methanol CH 3 OH Ethanol C 2 H 5 OH Propanol C 3 H 7 OH Butanol C 4 H 9 OH Pentanol C 5 H 11 OH Hexanol C 6 H 13 OH “functional group”

31 Ethanol Can be made by the addition reaction of water to ethene – when you have plenty of oil Phosphoric acid

32 Ethanol - Fermentation of sugars You can make ethanol for industry this way when you have lots of sugar cane

33 Dehydration of Ethanol

34 Ethanol and sodium 2C 2 H 5 OH + 2Na 2C 2 H 5 ONa + H 2 Hydrogen and sodium ethoxide formed

35 Oxidation of ethanol Ethanol can be oxidised to form ethanoic acid (acetic acid = vinegar!)

36 Carboxylic acids Methanoic acid CHOOH Ethanoic acid C 2 H 3 OOH Propanoic acid C 3 H 5 OOH Butanoic acid C 4 H 7 OOH Pentanoic acid C 5 H 9 OOH Hexanoic acid C 6 H 11 OOH

37 Carboxylic acids Methanoic acid CHOOH Ethanoic acid C 2 H 3 OOH Propanoic acid C 3 H 5 OOH Butanoic acid C 4 H 7 OOH Pentanoic acid C 5 H 9 OOH Hexanoic acid C 6 H 11 OOH “functional group”

38 Ethanol + ethanoic acid acids Ethanol + ethanoic acid ethyl ethanoate + water An ester (they normally smell nice!)

39 Ethyl ethanoate – an “ester”

40 Polymers

41 Polymers – addition polymerisation Molecules of ethene can be joined together to form polyethene ← monomers ← polymer

42 Polythene

43 Polypropylene – Strong and resistant to chemicals

44 poly(chloroethene) - PVC

45 Condensation polymers – Nylon Diamine + dicarboxylic acid ++ + monomers Reactive ends polymer Small molecules given off (HCl)

46 Cracking!

47 Too many long molecules Crude oil contains too many of the long (and not so useful molecules)

48 Cracking Luckily we can break the long molecules into shorter ones by “cracking” The long molecules are passed over hot broken pot (ceramic) and split up into smaller molecules. A catalyst can also be used

49 Cracking Cracking an alkane produces smaller alkanes and also alkenes.


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