What is ethanol?

Ethanol chemical structure showing CH3CH2OH.


Ethanol is an alcohol with the formula CH3CH2OH


It has three main uses:


  1. As a chemical feedstock to produce other organic compounds.
  2. As a biofuel (ethanol can be burned like petrol).
  3. Used in alcoholics drinks such as beer, wine, and spirits.

Ethanol can be produced from ethene and steam

Chemical equation showing ethene reacting with steam to produce ethanol with catalyst and high temperature conditions.

One way that ethanol is produced commercially is to react ethene (C2H4) with steam (gaseous H2O).


Type of reaction: Addition reaction because the water molecule is being added to the ethene molecule. 

Conditions: High temperature (300 °C), high pressure (60-70 atm), phosphoric acid catalyst.

Advantages: Ethene is cheap and the reaction itself is cheap and efficient. 

Disadvantages: Ethene is made from crude oil which is a non-renewable resource, so if it starts to run out it will become expensive.

Ethanol can be produced by fermentation

Chemical equation showing the conversion of glucose to ethanol and carbon dioxide.

Fermentation is the anaerobic respiration of sugars by yeast cells to produce ethanol and carbon dioxide.


Type of reaction: Anaerobic respiration (respiration without oxygen).

Conditions: Carried out in fermentation tanks. Requires yeast cells which have naturally occurring enzymes to catalyse the reaction. Temperatures of 30-40 °C (this is optimum temperature for the enzymes). Must be anaerobic conditions (no oxygen), so that the ethanol isn't oxidised to ethanoic acid.

Advantages: The sugar/glucose used is a renewable resource so can't run out. Yeast are easy to grow.

Disadvantages: The process can be relatively slow. The ethanol produced isn't pure so must be distilled by fractional distillation.

Illustration of a flask containing ethanol.

Give 3 uses of ethanol.

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Ethanol can be produced by fermentation.

Why are temperatures of 30-40 °C used?

Higher temperatures would evaporate the ethanol

Higher temperatures would be too expensive

This is the optimum temperature for the enzymes

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Ethanol can be produced by fermentation.

Write the symbol equation for this reaction. 

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