Journal of the American Chemical Society · 1960 · 54 citations · 0 references
The chemical shift of the methylene hydrogens in citric acid was measured as a function of the PH and the concentration of the solution. From these measurements it was possible to evaluate the chemical shifts associated with each ionization step in citric acid. Measurements were also made of methylene resonance line positions for ionized and non-ionized methyl ester of citric acid. Analysis of the results indicates that the first and second ionizations of citric acid take place predominantly at the terminal carboxyl groups.