An ester is formed when an alcohol is warmed with a carboxylic acid in the presence of an acid catalyst of concentrated sulfuric acid.
CH3CH2COOH + CH3OH -------------> CH3CH2COOCH3 + H2O
Propanoic acid + Methanol ------------> Methyl propanoate
In the reaction, the OH bond in the alcohol is broken and water is formed. The water molecule comes from the OH of the carboxylic acid group and the H in the alcohol group.
The first word comes from the alcohol and the second word comes from the carboxylic acid.
Esters are used in the chemical industry as adhesives and solvents. The flavours and fragrances of different esters are widely used to produce food flavourings and perfumes. The ester responsible for the smell of oranges is octyl ethanoate, and pentyl ethanoate provides a banana smell.
Dehydration of Alcohols
An alcohol can be dehydrated to form an alkene in the presence of an acid catalyst. This is an elimination reaction. Concentrated phosphoric acid, H3PO4, or concentrated sulfuric acid are suitable acid catalysts.
The alcohol is heated under reflux, in the presence of phosphoric acid, for about 40 minutes.