NMR study of sodium gluconate solutions

Aqueous solutions of sodium gluconate have been studied by 1D and 2D NMR spectroscopy. 1H NMR spectra of solutions demonstrate the fact that in the concentration range from 4 to 200 mmol/l the shapes of the lines corresponding to different groups of protons do not change. The 13C NMR spectrum proves that the structure of sodium gluconate molecules in aqueous solution is zigzag. Fitting of the computer-simulated 1H NMR spectra to the experimental ones made it possible to find the scalar J-coupling constants of vicinal protons and on the basis of them to determine the dihedral angles (HCC’H’) in sodium gluconate molecules. The scalar J-coupling constant of vicinal protons and the dihedral angles in sodium gluconate molecules also remain unchanged in the studied concentration range. Thus, unlike calcium gluconate solutions, the conformation of sodium gluconate molecules in aqueous solutions does not depend on concentration.