It is known that in alkaline solutions D-glucose undergoes three changes, namely: isomerization, dissociation and solvation; but the ^1^3C NMR spectra of D-glucose in neutral and alkaline solutions are almost without change. The ^1^3C NMR spectra of D-glucose, D-mannose and D-fructose at different pH values and the ^1H NMR spectra of D-glucose in neutral and alkaline aqueous solutions were determined. The chemical shifts of H(1) and H(2) were assigned by INDOR technique. They were compared with the net atomic charges obtained from EHMO calculations of the molecules, ions and hydrated ions. The results could be used to explain the fact of the absence of any changes in spectra.

Key words: DETERMINATION, NMR SPECTROMETRY, GLUCOSE, ISOMERIZATION REACTION, DISSOCIATION, SOLVATION