Unusual ion pairing by the trichloroacetate anion

Abstract

Nuclear magnetic resonance studies of the ³⁵Cl nucleus show conclusively that rather strong ion pairs are formed in aqueous solutions between the trichloro end of the trichloroacetate anion and either the hydrated proton or the tetramethylguanidinium cation. This confirms the explanation which was offered previously for the different values of the ionization constant of trichloroacetic acid which are obtained from dilute solution acidity measurements and from Raman spectral measurements of the carboxyl-ion concentrations.