When ethanol CH3CH2OH reacts with a carboxylic acid RCOOH in the presence of a mineral acid catalyst such as sulfuric acid, H2SO4 , an esterification reaction occurs. The product formed is an ester RCOOR' and water H2O .The mechanism of the reaction is as follows:1. Protonation of the carbonyl oxygen in the carboxylic acid by the mineral acid catalyst.RCOOH + H+ RCOOH2+2. Nucleophilic attack of the alcohol oxygen on the carbonyl carbon of the protonated carboxylic acid.RCOOH2+ + CH3CH2OH RCOOCH2CH3 + H2O3. Deprotonation of the oxonium ion intermediate by the alcohol or another carboxylic acid molecule.RCOOCH2CH3 + H2O RCOOCH2CH3 + H3O+The overall reaction is:RCOOH + CH3CH2OH RCOOCH2CH3 + H2OThe functional group present in the ester product is the ester group, which has the general structure -COOR' where R' is an alkyl group . In this case, the ester group is -COOCH2CH3.