Abstract: Of pyridinium chloridoacetic acid(1), N, N-dimethylanilinium chloridoacetic acid(2), 6-trimethylammonium chloridocaproic acid(3),.p-trimeth-ylammonium chloridobenzoic acid(4),and triethylammonium chloridoacetic acid(5),only the last one was transformed by treatment with thionyl chloride into its acid chloride(6), which was identified by converting to p-bromo-, p-iodo-,and 3,4-dimethylanilides.It seems that simple carboxylic acids bearing a quaternary ammonium chloride group are not easily transformed into their acid chlorides probably owing to their insolubility in both chlorinating agents and organic solvents.