Introduction

1. Introduction • What is the meaning of the following phrases? • “Organic” chicken • Raised without the use of drugs, hormones or synthetic chemicals • Organic lifestyle • - simple, healthy and close to nature

2. Bond Formation of Carbon Electronic structure of carbon is 1s22s22p2 Hence an atom of carbon has 4 valence electrons and it can form 4 covalent bonds by sharing electrons with 4 other atoms (H, O, N, S and halogens).

3. Homologous Series Organic compounds are classified into families of compounds known as homologous series. A homologous series is a series in which each successive member increases by the unit -CH2- . Compounds in the same homologous series have the following properities: a. have the same general formula Eg. The general formula of alkane, a homologous series is CnH2n+2.

4. Homologous series B Are different from the next member by a - -CH2 group.

5. Homologous series c. Show a gradual change in physical properties. As the number of carbon atoms in the molecule increases, - melting and boiling points increase - viscosity (ability to flow) increases d. Can be prepared by similar methods e. Have similar chemical properties because they have the same functional group.

6. Functional Group A functional group is any atom or group of atoms that gives the characteristic properties to a molecule and which defines the chemistry of an organic compound.

7. Functional Group Name ending Homologous series Functional group Nil (contain only single bonds) -ane Alkane

8. Name ending Homologous series Functional group -ene Alkene Functional Group Carbon - carbon double bond

9. Name ending Homologous series Functional group -ol Alcohol Functional Group Hydroxyl group

10. Name ending Homologous series Functional group -oic acid Carboxylic acid Functional Group Carboxyl group

11. Name ending Homologous series Functional group -oate ester Functional Group Ester group

12. Name ending Homologous series Functional group -amine amine Functional Group

13. Identify all the functional groups

14. Identify all the functional groups

15. Classifying and Naming The naming of is divided into two parts: a) first part tells the chain length, which is the no. of carbon atoms. Name start with No. of carbon atoms Meth- 1 eth- 2 pro- 3

16. Name start with No. of carbon atoms but- 4 5 6 Classifying and Naming Pent- Hex-

17. 2 carbon atoms alkane 4 carbon atoms alcohol Classifying and Naming 2. Second part shows the homologous series. Ethane An alkane with 2 carbon atoms Butanol An alcohol with 4 carbon atoms

18. Alkanes • saturated hydrocarbons • The general formula is CnH2n+2 • Hydrocarbons contain hydrogen and carbononly. • The names of alkanes end in -ane

19. Alkanes Structural formula Physical state Name Molecular formula Gas Bp = -162°C CH4 methane

20. Alkanes Structural formula Physical state Name Molecular formula Gas Bp = -89°C C2H6 ethane Condensed structural formula: CH3CH3

21. Structural formula Physical state Name Molecular formula Gas Bp = -42°C propane Alkanes C3H8 Condensed structural formula: CH3CH2CH3

22. Structural formula Physical state Name Molecular formula Gas Bp = -0.5°C Butane Alkanes C4H10 Condensed structural formula: CH3CH2CH2CH3

23. Alkanes

24. Alkanes (Page 3) Alkane with 5 carbon atoms = pentane Alkanes with 6 carbon atoms = hexane Alkanes with 7 carbon atoms = heptane

25. Alkanes (Page 3) Alkane with 8 carbon atoms = octane Alkanes with 9 carbon atoms = nonane Alkanes with 10 carbon atoms = decane Alkanes are often described to be saturated, they contain only carbon-carbon single bonds and contain the maximum no. of H atoms per carbon.

26. Properties of Alkanes (Pg 4) 1. Alkanes are covalent compounds. 2. They have low boiling points. Why? Alkanes are simple molecular compounds. The induced dipole-induced dipole forces between the molecules are weak and only a small amount of energy is needed to overcome these weak forces.

27. Properties of Alkanes 3. As the no. of carbon atoms in a molecule increases, the boiling point becomes higher.

28. Properties of Alkanes Alkanes are non-polar molecules. The intermolecular forces between the molecules are weak induced dipole-induced dipole forces . As the carbon chain gets longer, the no. of electrons increases, resulting in stronger induced dipole-induced dipole forces between the molecules, hence boiling point increases.

29. Properties of Alkanes • 4. As the no. of carbon atoms in a molecule increases, the alkane become more viscous. • 5. As the no. of carbon atoms in a molecule increases, the alkanes becomes less flammable. • Alkanes are usually • insoluble in water • 7. Alkanes are usually less dense than water.

30. Reactions of Alkanes • Alkanes are saturated and hence fairly unreactive. They undergo the following reactions: • Combustion • When combustion is complete, i.e., carried out in the presence of excess O2, alkanes burn to give carbon dioxide and water. • E.g combustion of butane – see white board • Alkanes are mostly used as • fuel as they produce energy when burnt. • Bottled gas which contains butane is used for cooking. Butane is also a fuel in cigarette lighter.

31. Reactions of Alkanes When combustion is incomplete, i.e. the supply of O2 is inadequate, the products are carbon monoxide, soot and Water. Example 2CH4 (g) + 3O2 (g)  2CO (g) + 4H2O (g) CH4 (g) + O2 (g)  C (s) + 2H2O (g)

32. Substitution with halogens Alkanes react with halogens in the presence of UV/sunlight . UV light is needed to start the reaction. It is used to break the covalent bonds in halogen molecule (E.g Cl2) to produce chlorine radicals. Cl-Cl  2Cl• The chlorine radicals are highly reactive and would attack the alkane molecule.

33. Substitution with halogens Example – Substitution of methane with chlorine CH4 (g) + Cl2 (g)  CH3Cl (g) + HCl (g) Or equation showing full structural formula: See white board.

34. Substitution with halogens

35. Formation of crude oil

36. Oil Rig

37. Fractional Distillation of petroleum, Pg 9 • Petroleum or crude oil is a complex mixture of 150 hydrocarbon molecules. • Separation of petroleum into useful fractions is called refining, and it is done in oil refineries. • Refining consists of 3 basic steps: • 1. *Fractional distillation of petroleum • 2. *Cracking • 3. Reforming (Eg Converting straight-chain alkanes into branched-chain alkanes)

38. 2nd step in Oil Refining

39. 3rd step in Oil Refining b

40. Oil Refineries in Singapore

41. Fractional Distillation of Petroleum, Pg 10 • The different components in the crude oil have different boiling points and fractional distillation separates the components as a result of this property. • Each fraction consists of a mixture of hydrocarbon molecules that boils over a range of temperature.

42. Fractional Distillation of Petroleum, Pg 9

43. Fractional Distillation

44. Cracking, Pg 10 A process in which involves splitting larger hydrocarbon molecules into smaller molecules by subjecting them to high temp and pressure, usually in the presence of a solid catalyst. Large hydrocarbons  short-chain alkanes + short-chain alkenes E.g C11H24  C2H4 + C9H20

45. Cracking

46. Thermal Cracking The alkanes are usually heated to a temperature between 500-800C.

47. Catalytic Cracking On the industrial scale, cracking is done by passing the petroleum fraction containing long chains of carbon atoms over aluminium oxide or silicon (IV) oxide catalyst at a temperature of about 600C.

48. Used to make plastics Uses of Cracking 1. The less useful large molecules are cracked to form smaller molecules like petrol as there is a greater demand for the smaller molecules. 2. Cracking is a way of making short-chain alkenes such as ethene or propene which are required to make plastics. C18H38 C6H14 + 6C2H4

49. Uses of Cracking • Cracking produces hydrogen as a by-product in oil refineries. The hydrogen can be used to make ammonia by Haber process. • Cracking tends to produce branched-chain rather than straight-chain alkanes, providing petrol with higher octane rating. • The petrol from the fractional distillation of petroleum contains a lot of straight-chain alkane, such as octane.

50. Cracking in the laboratory, Pg 11 The broken pot which contains aluminum oxide and silicon (IV) oxide acts as a Catalyst.