1. Alkenes (II)

2. Overview

4. Why do alkenes undergo addition reactions? Addition Reactions Carbon-carbon double bonds in alkenes are reactive. readily undergoes addition reactions

5. Addition Reactions + Unsaturated hydrocarbon Saturated organic compound In an addition reaction, carbon-carbon double bonds become single bonds. This means that an unsaturated hydrocarbon becomes a saturated organic compound.

6. Types of Addition Reactions H H H H H H + + + Br2 H2 H C C C C C C General Equation: H H H H H H H H H H H H OH H C C H H C C H H C C H Br Br H H H OH

12. Nutritional Facts Avoid foods high in saturated fat!

13. Nutritional data Avoid oils high in saturated fat. Opt for healthier options like sunflower oil!

14. Manufacture of Alkenes Short-chain alkenes are useful as starting materials for making ethanol and plastics. How can we manufacture alkenes? cracking By __________________ of petroleum Cracking is the _______________ of long-chain hydrocarbons into ___________________. On the industrial scale, cracking is done by passing the petroleum fraction over a _____________ (aluminium oxide or silicon(IV) oxide) at a _________________ of 600°C. breaking down smaller molecules catalyst temperature Cracking

15. Products of Cracking 3 possible types of products Try this: Write an equation for the cracking of heptane (C7H16). (Note: There are a few possible answers) One possible answer: C7H16 C3H6 + C4H8 + H2

16. Video time: Cracking in the school laboratory 3. Describe some characteristics of the gases collected. They have a smell, are flammable and unsaturated (contain C=C bonds). 4. Which other test can be used to test for unsaturation? Click here Add acidified potassium permanganate to the unknown. If it turns brown or colourless, the unknown is unsaturated. 1. What is the compound that is cracked? Paraffin 2. What is the catalyst used? 5. Why is the displacement of water method used to collect the products? Pumice stones / broken flower pots The organic products are insoluble in water.

17. Why the need for cracking? < Shortfall of petrol > Excess of fuel oil Cracking of heavier fractions like fuel oil can be used to make up for the shortfall of lighter fractions like petrol.

18. In short, cracking is used to produce: Hydrogen (fuel and raw material for Haber process) Petrol (fuel) Short-chain alkenes (starting materials for making ethanol and plastics)

19. Steam cracking adopted Produce large amounts of ethene, propene and butene for making plastics Cracking plants in Jurong island and PulauBukom In the Singapore context Steam cracking plant in Singapore Jurong island PulauBukom

20. 10 minutes to construct concept maps! Summary 1 2 3 Cracking