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) CH 3 OH (l) + 1½O 2 (g)  CO 2 (g) + 2H 2 O (l) C 3 H 7 OH (l) + 4½O 2 (g)  3CO 2 (g) + 4H 2 O (l)

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 + /Cr 2 O 7 2- During the reaction, the acidified potassium dichromate changes colour from orange to green.

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

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.

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.

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