Ethene is a colorless gas with the formula C2H4 that is mainly produced through the cracking of petroleum products and natural gas. It undergoes characteristic alkene reactions like addition and oxidation. Ethene is an important industrial chemical used to produce polymers like polyethene, polyvinyl chloride, and polystyrene that are used to make various plastic products, as well as in other applications like fruit ripening and as an antifreeze component.

1. Ethene

2. Properties Structural, Chemical and Physical General formula C n H 2n Non-polar Planar Double bond (alkene), reactive Molecule held together by dispersion forces Flammable Sweet odor Colourless gas Boiling point -104 o C Melting point -169 o C Molecular Weight 28.08 Heat of fusion 119.5 kJ/kg Heat of Combustion 47.183 MJ/kg Enthalpy of Formation 52.32 kJ/mol

3. Reactions Since ethene is an alkene, it follows some characteristic reactions of alkenes. Such reactions include: Addition reactions – With water, halogens, hydrogen halides, hydrogen - Halogenation and polymerization are both addition reactions Oxidation reactions - When using potassium permanganate as the oxidant, products of reaction are dependent on the pH condition of the KMnO 4 - Acidic = purple to colourless - Basic/neutral = purple to dark green with brown precipitate Combustion reaction - The usual. Reacts with oxygen, carbon dioxide and water vapour formed.

4. How is ethene manufactured? Two sources: - Natural Gas - Crude Oil Thermal/Steam cracking - Process: 1. Feedstock and steam fed into coiled tube in furnance, 750 – 900 o C. 2. Then passed into cooler at -100 o C. Gases then separated by distillation.

5. … and continuing An example of a typical cracking reaction: Ethane forms ethene through the cracking procedure. C2H6 (g)  C2H4 (g) + H2 (g) ∆H = + 138 KJ/mol Maximum yield at: - High temperature - Pressure just below the atmosphere pressure Other methods of manufacture: Dehydration of ethanol - Presence of a catalyst (sulfuric acid, aluminium oxide, zeolite catalyst) Using cellulose as a raw material - Too costly. In every singly way imaginable.

6. Hazards of ethene Escapes into the environment by: - From its production - Cigarette smoke - Waste incineration - Vehicle wastes Hazards of use - Gas state – Especially highly flammable and explosive - Prolonged exposure can harm the brain, if inhaled - Liquid state – Very cold, risk of frostbite Sniffing ethene result in: - light-headedness, dizziness, unconsciousness, and suffocation Kaboom?

7. Environmental Hazards Low concentrations – No negative harm High concentrations – Affect growth of plant life. Ethene = Ripening agent Causes – Fruit to ripen quickly - Leaves to fall off more quickly - Stunted growth Disposing: - Via burning preferable to releasing into atmosphere

8. Industrial Uses Fruits and Plastic Fruits - Ethene produced by fruits - Allows the fruit to ripen - Rate of ripening can be control by controlling ethene levels

9. Polymerization Polymerization = reaction where monomers join together to form a large chain molecule = formation of plastic Monomers such as ethene, vinyl chloride and styrene polymerize to form polymers which can be used for many applications. Polyethene – Used in plastics Polyvinyl chloride (PVC) – thermoplastic - additives sometimes added - used in wire coatings, packaging and many more Polystyrene – hard - transparent - found in food cups and plastic containers etc

10. More more more and more uses As antifreeze - Main component - ethylene glycol - Aqueous ethylene glycol used in car radiators Formation of ethanol - Ethene reacts with water in the presence of a catalyst to form ethanol - Ethanol then used as solvent in : - Inks - Cosmetics - Pharmaceuticals

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