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What is combustion? Write a definition Write an equation of combustion for

What is combustion? Write a definition Write an equation of combustion for the following alcohols: Ethanol Methanol Propanol. Combustion – The process of burning by reacting a fuel with oxygen C 2 H 5 OH (l) + 3O 2 (g) 2CO 2 (g) + 3H 2 O (l)

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What is combustion? Write a definition Write an equation of combustion for

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  1. What is combustion? • Write a definition • Write an equation of combustion for • the following alcohols: • Ethanol • Methanol • Propanol

  2. Combustion – The process of burning by reacting a fuel with oxygen • C2H5OH (l) + 3O2 (g)2CO2 (g)+ 3H2O (l) • CH3OH (l) + 1½O2 (g)CO2 (g)+ 2H2O (l) • C3H7OH (l) + 4½O2 (g)3CO2 (g)+ 4H2O (l)

  3. Oxidation of Alcohols

  4. Oxidation of Alcohols • Primary and secondary alcohols can be oxidised using an oxidising agent. • Suitable oxidising agent is a solution containing acidified dichromate ions H+ /Cr2O72- • During the reaction, the acidified potassium dichromate changes colour from orange to green.

  5. Alcohols fall into different classes depending on how the -OH group is positioned on the chain of carbon atoms • In a primary (1°) alcohol, the carbon which carries the -OH group is only attached to one alkyl group. • In a secondary (2°) alcohol, the carbon with the -OH group attached is joined directly to two alkyl groups

  6. Primary Alcohols • On gentle heating with potassium dichromate a primary alcohol can be oxidised to produce an aldehyde. On stronger heating in excess acidified dichromate alcohol will pass through aldehyde stage to form carboxylic acid.

  7. Reflux – the continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry.

  8. Secondary and Tertiary Alcohols • Oxidised by dichromate ions to produce ketones. • Tertiary alcohols are resistant to oxidation so don’t react. Ketones can’t be oxidised any further

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