Butanoate anion is a weak base and will partially ionize in water to give butanoic acid and hydroxide ions: CH3CH2CH2COO + H2O <=> CH3CH2CH2COOH + OH Solution Butanoate anion is a weak base and will partially ionize in water to give butanoic acid and hydroxide ions: CH3CH2CH2COO + H2O <=> CH3CH2CH2COOH + OH.