Preparation of ethanol

Production of ethanol in the industry

• Addition reaction with water (steam)
  • Catalyst: phosphoric acid
  • Temperature: 300°C 
  • Pressure: 60 atm 

\(C_2H_4(g) + H_2O(l) \xrightarrow[]{H_3PO_4} C_2H_5OH(l)\)

 

Production of ethanol in the laboratory

• The fermentation process of carbohydrate or sugary substances like rice, barley or fruits
  • These substances contain glucose.
  • Zymase in yeast acts as a catalyst to convert glucose to ethanol. 

\(C_6H_{12}O_6(aq) \xrightarrow[]{yeast} 2C_2H_5OH(l) + 2CO_2(g)\)

 

Chemical properties of ethanol

• Combustion
  • Combustion of ethanol in excess oxygen produces carbon dioxide and water. 

\(C_2H_5OH(l) + 3O_2 (g) \rightarrow 2CO_2(g) + 3H_2O(l)\)

 

• Oxidation
  • Ethanol is oxidised by acidified potassium dichromate(VI) solution.
  • Product: ethanoic acid
  • Dichromate ion (orange) changes to chromium ion (green). 

\(C_2H_5OH(l) \xrightarrow[]{[O]} CH_3COOH(l)\)

 

• Dehydration
  • A water molecule is eliminated from the reaction.
  • Catalyst: sulphuric acid
  • Temperature: 180°C 
  • Product: ethene 

\(C_2H_5OH(l) \xrightarrow[]{H_2SO_4, 180^\circ C} C_2H_4(g) + H_2O(l)\)