When propanoic acid C3H6O2 reacts with sodium hydroxide NaOH , the product formed is sodium propanoate C3H5O2Na and water H2O . This is an acid-base neutralization reaction. The balanced equation for the reaction is:C3H6O2 + NaOH C3H5O2Na + H2OThe functional group present in the product, sodium propanoate, is the carboxylate ion COO- which is a deprotonated carboxylic acid COOH group.