Alcohols

Hydration of Ethene

• steam
• 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

• Fermentation
• 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%.

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.

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

When a primary alcohol is heated more strongly with excess acidified dichromate the alcohol is completely oxidised to form a carboxylic acid.

REFLUX

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.

• Plenty of oxygen needed
• Forms carbon dioxide and water
• Incomplete combustion can form carbon monoxide

 Combustion of ethanol with plentiful supply of oxygen...