Ethene

PropertiesPropertiesStructural, Chemical and Physical

• General formula CnH2n

• Non-polar

• Planar

• Double bond (alkene), reactive

• Molecule held together by dispersion forces

• Flammable

• Sweet odor

• Colourless gas

• Boiling point -104 oC

• Melting point -169 oC

• 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

ReactionsReactions Since ethene is an alkene, it follows some characteristic Since ethene is an alkene, it follows some characteristic

reactions of alkenes.reactions of alkenes.Such reactions include:Such reactions include:• Addition reactionsAddition reactions – – With water, halogens, hydrogen halides, hydrogenWith water, halogens, hydrogen halides, hydrogen - Halogenation and polymerization are both addition reactions- Halogenation and polymerization are both addition reactions• Oxidation reactionsOxidation reactions - When using potassium permanganate as the oxidant, - When using potassium permanganate as the oxidant,

products of reaction are dependent on the pH condition of the products of reaction are dependent on the pH condition of the KMnOKMnO44

- Acidic = purple to colourless- Acidic = purple to colourless

- Basic/neutral = purple to dark green with brown precipitate- Basic/neutral = purple to dark green with brown precipitate• Combustion reactionCombustion reaction - The usual. Reacts with oxygen, carbon dioxide and water - The usual. Reacts with oxygen, carbon dioxide and water

vapour formed.vapour formed.

How is ethene How is ethene manufactured?manufactured?

• Two sources:Two sources:

- Natural Gas - Natural Gas

- Crude Oil- Crude Oil• Thermal/Steam crackingThermal/Steam cracking

- Process:- Process:

1. Feedstock and steam fed into coiled tube in furnance, 750 – 1. Feedstock and steam fed into coiled tube in furnance, 750 – 900900oC.

2. Then passed into cooler at -100 oC. Gases then separated by Gases then separated by distillation.distillation.

… … and continuingand continuing• An example of a typical cracking reaction: Ethane forms An example of a typical cracking reaction: Ethane forms

ethene through the cracking procedure.ethene through the cracking procedure.C2H6 (g) C2H6 (g) C2H4 (g) + H2 (g) ∆H = + 138 KJ/mol C2H4 (g) + H2 (g) ∆H = + 138 KJ/mol

• Maximum yield at:Maximum yield at: - High temperature- High temperature

- Pressure just below the atmosphere pressure- Pressure just below the atmosphere pressure

Other methods of manufacture:Other methods of manufacture:• Dehydration of ethanolDehydration of ethanol

- Presence of a catalyst (sulfuric acid, aluminium oxide, zeolite - Presence of a catalyst (sulfuric acid, aluminium oxide, zeolite catalyst)catalyst)

• Using cellulose as a raw materialUsing cellulose as a raw material

- Too costly. In every singly way imaginable.- Too costly. In every singly way imaginable.

Hazards of etheneHazards of ethene

• Escapes into the environment by:Escapes into the environment by:

- From its production- From its production

- Cigarette smoke- Cigarette smoke

- Waste incineration- Waste incineration

- Vehicle wastes- Vehicle wastes• Hazards of useHazards of use

- Gas state – Especially highly flammable and explosive- Gas state – Especially highly flammable and explosive

- Prolonged exposure can harm the brain, if inhaled- Prolonged exposure can harm the brain, if inhaled

- Liquid state – Very cold, risk of frostbite- Liquid state – Very cold, risk of frostbite• Sniffing ethene result in:Sniffing ethene result in:

- light-headedness, dizziness, unconsciousness, and suffocation - light-headedness, dizziness, unconsciousness, and suffocation

Kaboom?

Environmental HazardsEnvironmental Hazards• Low concentrations – No negative harmLow concentrations – No negative harm• High concentrations – Affect growth of plant life.High concentrations – Affect growth of plant life. • Ethene = Ripening agentEthene = Ripening agent

Causes Causes – Fruit to ripen quickly– Fruit to ripen quickly

- Leaves to fall off more quickly- Leaves to fall off more quickly

- Stunted growth- Stunted growth• Disposing:Disposing:

- Via burning preferable to releasing into atmosphere- Via burning preferable to releasing into atmosphere

Industrial UsesIndustrial Uses• Fruits and PlasticFruits and Plastic• FruitsFruits

- Ethene produced by fruits- Ethene produced by fruits

- Allows the fruit to ripen- Allows the fruit to ripen

- Rate of ripening can be control by controlling ethene - Rate of ripening can be control by controlling ethene levelslevels

PolymerizationPolymerization• Polymerization Polymerization = reaction where monomers join together to = reaction where monomers join together to

form a large chain moleculeform a large chain molecule = formation of plastic= formation of plastic• Monomers such as ethene, vinyl chloride and styrene polymerize Monomers such as ethene, vinyl chloride and styrene polymerize

to form polymers which can be used for many applications.to form polymers which can be used for many applications.• PolyethenePolyethene – Used in plastics – Used in plastics• Polyvinyl chloride (PVC)Polyvinyl chloride (PVC) – thermoplastic – thermoplastic - additives sometimes added- additives sometimes added - used in wire coatings, packaging and - used in wire coatings, packaging and many moremany more• PolystyrenePolystyrene – hard – hard - transparent- transparent - found in food cups and plastic containers etc- found in food cups and plastic containers etc

More more more and more More more more and more usesuses

• As antifreezeAs antifreeze

- Main component - ethylene glycol- Main component - ethylene glycol

- Aqueous ethylene glycol used in car radiators- Aqueous ethylene glycol used in car radiators

• Formation of ethanolFormation of ethanol

- Ethene reacts with water in the presence of a catalyst to - Ethene reacts with water in the presence of a catalyst to form ethanolform ethanol

- Ethanol then used as solvent in :- Ethanol then used as solvent in :

- Inks- Inks

- Cosmetics- Cosmetics

- Pharmaceuticals - Pharmaceuticals

Thank you (: