Anisotropic Reorientation and Intermolecular Interactions of Sucrose Molecules in Aqueous Solution. A Temperature and Concentration-Dependent ~(13)C NMR Relaxation Study

摘要

The reorientational dynamics of sucrose in aqueous solutions were investigaged by measurement of ~(13)C spin-lattice relaxation times for several different concentrations from 0.1 to 4.0 mol kg~(-1) and in a temperature range between 298 and 328 K. The relaxation data were used as input to evaluate the reorientational correlation time and rotational diffusion constants. The correlation times and rotational diffusion constants follow an Arrhenius law in the observed temperature range with activation energies from 22 to 46 kJ mol~(-1) at 0.1-4.0 mol kg~(-1), respectively. It was shown that the rotational motion of sucrose molecules in aqueous solution is anisotropic, and the anisotropy of the molecular reorientation turned out to be concentration-dependent. The concentration dependence reflects the change in the intermolecular interactions of the sucrose from mainly water-sucrose interactions to a mixture of water=sucrose and sucrose-sucrose interactions. It was thus possible to detect sugar-sugar interactions, which are of biological relevance.