Epoxyethane (Oxford AQA International A Level (IAL) Chemistry): Revision Note

Production & Reactions of Epoxyethane

Production of epoxyethane

• Epoxyethane, C₂H₄O, is an important industrial chemical which is used to make many useful products

• It is produced by the partial oxidation of ethene using a silver catalyst

The structure of epoxyethane

• Producing epoxyethane can be a hazardous process due to the very reactive nature of the substance:

  • Usually when carbon atoms form single bonds, the bond angle is 109.5^o but every bond in epoxyethane is approximately 60^o

  • This bond angle creates repulsion between the bonding pairs of electrons

  • As a result the bonds break very easily and the ring opens up to become more stable in a process known as 'ring strain' making epoxyethane very reactive

Reactions of epoxyethane

With water

• Epoxyethane reacts with water to form ethane-1,2-diol

  • Ethane-1,2-diol is used as antifreeze in cars

• During this reaction:

  • The oxygen atom in epoxyethane is protonated

  • Then, the OH^- ion attacks the positive carbon (C+) in the carbocation

• A range of polymers can be formed by further reactions shown here:

• n= 1, ethane-1,2-diol is used as antifreeze

• n=2, diethylene glycol is used to make polyurethanes and polyesters

• n=3, triethylethene glycol is usd to make plasticisers

• n=4 or more, polyethylene glycol (PEG) is used to make detergents, paints and cosmetics

With alcohol

• Alcohols react with epoxyethane to form products which can be used as solvents, plasticisers and detergents

• The general equation for the reaction between epoxyethane and alcohol is:

  

  • where R is is an alkyl group

• The product formed is an alcohol as there is still an OH group present

• If the alcohol is added in excess the reaction continues to form further products with longer polymer chains

• We get important products from the reactions of epoxyethane including, surfactants and antifreeze

Economic and environmental importance of products

• The products formed from these reactions have significant economic and environmental roles

1. Antifreeze (ethane-1,2-diol)

Economic importance:

• Ethane-1,2-diol is the main component of antifreeze used in car cooling systems

  • It disrupts the hydrogen bonding in water, significantly lowering the freezing point of the coolant

  • This prevents the water from freezing and expanding in cold weather, which would otherwise crack the engine block, leading to very expensive repairs

Environmental importance:

• Ethane-1,2-diol is toxic if ingested

• Spills must be cleaned up, and old antifreeze must be disposed of carefully to prevent it from contaminating water supplies and harming wildlife

2. Surfactants and Detergents

Economic importance:

• Longer chain molecules made from the reaction of epoxyethane with alcohols are used to produce surfactants

  • Surfactants are the active ingredient in soaps and detergents, which are essential for cleaning and hygiene in households and industry

  • They work because they have a hydrophilic ("water-loving") head and a hydrophobic ("water-hating") tail, allowing them to break down grease and oils

Environmental importance:

• The environmental impact of surfactants is a major consideration

• Modern detergents are designed to be biodegradable to prevent them from persisting in the environment and causing issues like foaming in rivers