The Interaction Between Ionic Liquid And Monosaccharide In Water

Extensive applications of ionic liquids (ILs) may result in their accumulation in the ecologicalenvironment and organism. Although ILs are popularly called "green solvents", their toxicity, in fact, hasbeen exhibited. Saccharides (S) are a type of important biomolecules and chemical materials. In this thesis,the dependences of the IL S interactions on the stereochemical structure of saccharides and ILs wereexplored, and the influences of ILs on the stereo-structures of saccharide molecules which interact with ILswere studied. Results thus-obtained are very important to interpret the interaction between saccharides andILs in organism, and provide some theoretical foundations and basic data on the accumulation of ILs inorganism and their potential toxicity. At the same time, this work will also provide some theoreticalfoundations and basic data for the extraction, purification and synthesis of saccharides, and fordevelopment, designment and optimization of correlative producing processes. This work was supportedfinancially by the National Natural Science Foundation (No.20973055) and the Innovator Foundation ofthe Colleges and Universities of Henan Province. The major contents and conclusions are as follows:1. Conductivities of1-alkyl-3-methylimidazolium chloride ionic liquids ([Cnmim]Cl, n=4,6,8,10) inaqueous glucose solutions and [C₄mim]Cl in aqueous monosaccharide (glucose, galactose, xylose, andribose) solutions were measured at298.15K. The limiting molar conductivities (Λ₀) and associationconstants (KA) were derived from the Lee–Wheaton conductivity equation. Using the obtained conductivitydata, the values of the Walden product (Λ₀η0) were also calculated. The IL monosaccharide interactionswere discussed in terms of the alkyl chain length of the cations of the ILs and the stereo-chemistry of themonosaccharide molecule. It is shown that:1) at given molalities of the monosaccharides, the Λ₀valuesfollow the order: glucose and galactose (hexose)<xylose and ribinose (pentose);2) at given molalities ofthe glucose, the Λ₀values decrease linearly with increasing alkyl chain length of the ILs.2. The interactions of1-butyl-3-methylimidazolium carboxylate ionic liquids ([C₄mim][HCOO],[C₄mim][CH₃COO] and [C₄mim][CH₃CH₂COO]) with glucose in water were studied by volumetry,viscosity, conductivity and NMR. Limiting apparent molar volumes (V_Φ,IL⁰), viscosity B-coefficients,limiting molar conductivities (Λ₀) and Walden products (Λ₀η0) were evaluated for the ILs in glucose+water solutions, respectively. Volumetric interaction parameters were also obtained from the transfer volumes ofthe ionic liquids. The contributions of the solvent properties (B1) and the ionic liquid-solvent interaction (B₂)to the B-coefficient were extracted together with molar activation energies (Δ μ0≠IL) of the ionic liquids forviscous flow of the aqueous glucose+IL solutions. In addition, the13C and1H NMR spectra of methylβ-D-glucopyranoside and ILs in ternary β-D-glucopyranoside+IL+D2O were studied. The interactionswere discussed in terms of the size, structure and solvation of the ILs and glucose. It is shown that theIL glucose interactions are in the order:[C₄mim][CH₃CH₂COO]>[C₄mim][CH₃COO]>[C₄mim][HCOO].3. Structures of the complexes (glucose and anions:[HCOO]-,[CH₃COO]-and [CH₃CH₂COO]-) wereoptimized at the B3LYP/6-31+g(d,p) level and fully characterized as minima by frequency analysis at thesame level. The results were consistent with those obtained by volumetry, viscosity, conductivity and NMR.4. The densities and viscosities for the geminal dicationic ionic liquids ([C₄(mim)₂]Br₂,[C₅(mim)₂]Br₂and [C6(mim)₂]Br₂)+glucose+water systems were measured at298.15K. Limiting apparent molarvolumes (V_Φ,IL⁰) and viscosity B-coefficients were evaluated for the ILs in glucose+water solutions,respectively. Volumetric interaction parameters and molar activation energies (Δ μ0≠IL) were also obtained.The interaction between ILs and glucose is in the order:[C₆(mim)₂]Br₂>[C₅(mim)₂]Br₂>[C₄(mim)₂]Br₂.5. The aggregation behavior of1-decyl-3-methylimidazolium chloride ([C₁₀mim]Cl) was investigatedin aqueous monosaccharide (glucose, galactose, xylose and arabinose) solutions by conductivity,fluorescence, NMR and dynamic light scattering (DLS). The critical aggregation concentration (CAC),ionization degree of the aggregates (α), the standard Gibbs energy of aggregation (ΔGm⁰), and theaggregation number (N) were derived from the experimental data. The results show that addition of smallamounts of monosaccharides to aqueous solution can cause a variation in aggregation properties of the IL.The CAC values decrease with increasing molality of monosaccharides. In particular for different kinds ofmonosaccharides, we found that the CAC values are in the order: glucose> galactose (hexoses), xylose>arabinose (pentoses); xylose> glucose (1e2e3e4e), arabinose> galactoses (1e2e3e4a). These trends may beattributed to the slight difference in the stereo-structure of monosaccharide molecules.