Application of NMR at various nuclei to determine the composition and structure of complexes in the trifluoroacetic acid-water system

Analysis of the family of concentration relationships for the¹H,²H,¹³C,¹⁷O, and¹⁹F NMR chemical shifts made it possible to establish that 3:1, 2:2, and 1:2 molecular complexes are formed in the trifluoroacetic acid-water system. The NMR chemical shifts of these complexes were determined. The probability distribution of these complexes in relation to the concentration of the components was calculated. The concentration dependence of the degree of dissocation of trifluoroacetic acid was determined in the range of 0–33 mole % of the acid. While not affecting the distribution of the molecular complexes, substitution of the exchange proton by a deuteron affects the ionization process, reducing the amount of ionic particles.L. Ya. Karpov Scientific-Research Physicochemical Institute, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 1, pp. 75–83, January–February, 1991. Original article submitted January 30, 1989.