The strength of acid is determined by its ability to produce H⁺ in solutions. Unlike mineral acids, the carboxylic acids (of the form RCOOH) do not completely ionise. They partially ionise to give H⁺ and RCOO^-. Therefore they are called weak acids.

Methanol on oxidation in the presence of a strong oxidising agent like alkaline KMnO₄ produces methanoic acid.