Evidence of two-step deprotonation of D-mannitol in aqueous solution

Ernestas Gaidamauskas; Eugenijus Norkus; Jūrate Vaiciūniene; Debbie C Crans; Tapani Vuorinen; Jane Jaciauskiene; Gintaras Baltrūnas

doi:10.1016/j.carres.2005.03.006

Evidence of two-step deprotonation of D-mannitol in aqueous solution

Carbohydr Res. 2005 Jun 13;340(8):1553-6. doi: 10.1016/j.carres.2005.03.006.

Authors

Ernestas Gaidamauskas¹, Eugenijus Norkus, Jūrate Vaiciūniene, Debbie C Crans, Tapani Vuorinen, Jane Jaciauskiene, Gintaras Baltrūnas

Affiliation

¹ Vilnius University, Faculty of Chemistry, Vilnius, Lithuania. ernestas.gaidamauskas@chf.vu.lt

PMID: 15882852
DOI: 10.1016/j.carres.2005.03.006

Abstract

Deprotonation of D-mannitol was studied in aqueous basic solutions by means of potentiometry and (13)C NMR spectroscopy. Two-step dissociation in the pH range from 12 to 13.8 was shown, and successive dissociation constants K(a1) and K(a2) were determined. In a solution with ionic strength I = 1.0 M (NaOH + NaNO(3)) pK(a1) = 13.1 +/- 0.1 and pK(a2) = 13.8 +/- 0.2. With increasing ionic strength from 0.75 to 3.0 M, both pK(a1) and pK(a2) values decrease. Deprotonation-induced chemical shifts in pH-variable (13)C NMR spectra show that the OH-groups next to internal carbon atoms C-3 and C-4 dissociate to a greater extent compared to OH-groups next to external carbon atoms C-1 and C-6.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Hydrogen-Ion Concentration
Magnetic Resonance Spectroscopy
Mannitol / chemistry*
Molecular Structure
Protons
Solutions / chemistry
Water / chemistry*

Substances

Protons
Solutions
Water
Mannitol