Ground state vibrations of citric acid and the citrate trianion-an ab initio study

Ab initio force fields for the vibrations of citric acid and citrate trianion in their ground electronic states have been determined at the Hartree-Fock level using the 4-21G basis set. The calculated geometries have been compared to the corresponding X-ray structures of citric acid and magnesium citrate, respectively. The calculated vibrational frequencies have been used to assign the experimental IR and Raman spectra of citric acid and sodium citrate. The calculated potential energy distribution, Raman activities and IR intensities have been used as aids in the assignment of the vibrational spectra of citric acid and sodium citrate.