Hydration of Ethene
- phosphoric acid catalyst
- This reaction is reversible, only 5% of ethene is converted to ethanol so unreacted gases are recyled to create a 95% conversion
- Carbohydrates (sugar/starch)
- 37ºC(so enzyme Zymase in yeast doesn't denature)
- anaerobic(Presence of air may produce ethanal / ethanoic acid)
- The toxicity of alcohol limits the concentration of ethanol to approx 14%.
Uses of Alcohols
Alcohols can be used in:
- Alcoholic drinks such as beer, wine and spirits
- Ethanol as fuel - It can be blended with petroleum to increase the octane rating so it burns more cleanly
- Methylated spirits - Mixed with methanol and coloured dye for use as fuel, spirit burners, camping stoves and to remove paint or ink stains
- Methanol is highly toxic and ingestion can lead to severe organ damage and death. It is a clean-burning fuel used as an additive in racing cars.
These are influenced by ability to make H-bonds between O-H groups.
Volatility - Decreases as chain length increases
Solubility - Decreases as chain length increases
- Only first 3 alcohols are soluble (methanol, ethanol and propanol)
This is because as the chain length increases a larger part of the molecule is non-polar and cannot form hydrogen bonds with water molecules.
Primary Alcohol - Distillation
In these alcohols the -OH is bonded to a carbon with 1 or 0 alkyl groups.
DISTILLATION: Heated gently with acidified
potassium dichromate to produce an ALDEHYDE
Primary Alcohols - Reflux
When a primary alcohol is heated more strongly with excess acidified dichromate the alcohol is completely oxidised to form a carboxylic acid.
Product = Carboxylic Acid
In a secondary alcohol the -OH group is bonded to a carbon that has 2 other alkyl groups.
To oxidise a secondary alcohol you must use REFLUX apparatus
The product is a KETONE!
In these alcohols the -OH group is bonded to a carbon atom with 3 other alkyl groups.
Because of this the tertiary alcohols are resistant to oxidation.
Combustion of Alcohols
- Plenty of oxygen needed
- Forms carbon dioxide and water
- Incomplete combustion can form carbon monoxide
Combustion of ethanol with plentiful supply of oxygen...