Yasuhiro Uosaki

Excess molar volumes of (a cyclic amide + water) at 298.15 K and 308.15 K

Abstract Excess molar volumes V m E for the binary mixtures of 2-pyrrolidinone, 1-methyl-2-pyrrolidinone, 3-methyl-2-oxazolidinone, and 1,3-dimethyl-2-imidazolidinone with water have been determined by use of bicapillary pyknometers at 298.15 and 308.15 K over the entire composition range. In all mixtures, the excess molar volumes are negative over the whole mole-fraction range. The minimum value of V m E decreases in the order: 3-methyl-2-oxazolidinone > 2-pyrrolidinone > 1-methyl-2-pyrrolidinone > 1,3-dimethyl-2-imidazolidinone. This order is discussed from the viewpoint of the difference in strength of the interaction of water with the carbonyl oxygen in the organic compounds.

Compressions of some amides at pressures up to 200 MPa and at the temperature 298.15 K

Compressions k of formamide (F), N -methylformamide (NMF), N,N -dimethylformamide (DMF), N,N -dimethylacetamide (DMA), and 1-methylpyrrolidin-2-one (MP) were measured at pressures up to 200 MPa and at the temperature 298.15 K. The experimental compressions were fitted to the Tait equation. Isothermal compressibilities κ T at the pressure 0.1 MPa for amides were evaluated from the Tait parameters. The κ T values for amides at 0.1 MPa decrease in the sequence: DMF ⩾ DMA > NMF > MP > F. The sequence of κ T values for aliphatic amides is discussed from the viewpoint of liquid structure.

Compressions of (water + a C3 alkanol) and (water + an alkan-1,2-diol) at the temperature 298.15 K and pressures up to 200 MPa

Abstract Compressions of {water + (propan-1-ol or propan-1,3-diol or glycerol or ethan-1,2-diol or propan-1,2-diol)} at the temperature 298.15 K and pressures up to 200 MPa have been measured over the whole range of composition. Experimental compressions as a function of pressure for mixtures of fixed composition were fitted to the Tait equation; the values of the Tait parameters evaluated, together with available densities at 0.1 MPa for each mixture, were used to calculate the isothermal compressibility. The composition dependences of isothermal compressibilities and excess molar volumes for the mixtures are discussed from the viewpoint of the effect of changing hydrophobic character of the alkanol molecules.

(Liquid + liquid) equilibria of (water + ethanol + n-hexane) from 0.1 to 200 MPa at 298.15 K

Abstract Tie lines for (water + ethanol + n -hexane) have been determined in the range 0.1 to 200 MPa at 298.15 K. The binodal curves obtained from the results show that the immiscibility region enlarges slightly at elevated pressures. Ethanol is preferentially dissolved in the aqueous phase and its mole fraction increases considerably in that phase (rather than in the organic phase) with increasing pressure. The distribution coefficient D 2 , defined as the ratio of the mole fraction x ′ 2 of ethanol in the aqueous phase to that x ″ 2 in the organic phase, is very large in the region of lower x ″ 2 values, depending on pressure; with an increase of x ″ 2 , however, D 2 reduces sharply and becomes independent of pressure. The tie lines at each pressure were satisfactorily correlated by the method of Othmer-Tobias on a mass-fraction basis.

Effect of water content on conversion of D-cellobiose into 5-hydroxymethyl-2-furaldehyde in a dimethyl sulfoxide-water mixture.

Noncatalytic conversion of D-cellobiose (at 0.5 M) into 5-hydroxymethyl-2-furaldehyde (5-HMF), a platform chemical for fuels and synthetic materials, was analyzed at 120-200 °C over a wide range of water mole fraction, xw = 0.007-1 in a binary dimethyl sulfoxide (DMSO)-water mixture by means of the in situ (13)C NMR spectroscopy. Effects of the water content were revealed as follows: (i) The tautomerization of the anomeric residue of D-cellobiose from D-glucose to D-fructose type was not initially observed at a lower water content, in contrast to the significant tautomerization into the D-fructose type in a higher water content and pure water. (ii) The lower the water content, the faster the glycosidic-bond cleavage by hydrolysis, because of the high reactivity of solitary water molecules with the large partial charges more naked as in supercritical water clusters due to the isolation by the organic solvent DMSO. (iii) The amount of D-fructose as the intermediate product was larger at the higher xw; despite the increase of D-fructose, the production of 5-HMF from D-fructose was slowed down. (iv) A high 5-HMF yield of 71% was reached at xw = 0.20-0.30 that was 6-10 times the initial D-cellobiose concentration. The best yield of 5-HMF was attained in the low xw region when the polymerization paths into NMR-undetectable species via 5-HMF and anhydromonosaccharides were effectively suppressed. This study provides a new framework to design optimal, noncatalytic reaction process to produce 5-HMF from cellulosic biomass by tuning the water content as well as the temperature and the reaction time.

Compressions of (water + formamide or N, N-dimethylformamide) at pressures up to 150 MPa and at the temperature 298.15 K

Compressions k of (water + formamide or N, N-dimethylformamide) were measured over the whole mole-fraction range at pressures up to 150 MPa and at the temperature 298.15 K. The experimental compressions for each mixture were fitted to the Tait equation. Isothermal compressibilities κT for the mixtures at a given pressure are evaluated from the Tait parameters. The composition dependence of k and κT values obtained for each aqueous amide mixture shows a similar behaviour at each pressure. Excess molar volumes VEm at high pressures are calculated from the compressions in combination with the reported densities at the pressure 0.1 MPa. Partial molar volumes Vi of the components i for both aqueous mixtures at a given pressure and their pressure derivative (∂Vi/∂p)T at the pressure 0.1 MPa are evaluated as a function of mole fraction. For aqueous N, N-dimethylformamide, the composition dependence of (∂Vi/∂p)T is compared with that of (∂Vi/∂p)S found in the literature. The changes in the excess molar Gibbs energy ΔGEm(p) at each pressure are evaluated from the pressure dependence of the VEm values. Pressure dependence of ΔGEm(p) for (0.5H2O + 0.5HCONR2) and for other aqueous organic mixtures is compared. The above thermodynamic properties are discussed from the viewpoint of molecular interaction between water and amide molecules.

Excess molar volumes of (1,1,3,3-tetramethylurea + an alkan-1-ol) at the temperature 298.15 K

Excess molar volumes VEm for (1,1,3,3-tetramethylurea + methanol or ethanol or propan-1-ol or butan-1-ol) have been obtained from density measurements at the temperature 298.15 K over the whole mole-fraction range. The excess molar volumes for all the mixtures are negative and decrease in magnitude with an increase of alkyl-chain length of the alkan-1-ol molecule. The VEm values for (1,1,3,3-tetramethylurea + an alkan-1-ol) are compared with those reported for (N,N-dimethylacetamide + an alkan-1-ol).

Compressions of nitro-compounds at pressures up to 150 MPa and at the temperatures 298.15 K and 323.15 K

Compression k of nitromethane, nitroethane, 1-nitropropane, 2-nitropropane, and nitrobenzene were measured at 298.15 and 323.15 K up to 150 MPa. The Tait equation was used to fit the experimental compressions. Isothermal compressibilities κT at 0.1 MPa were determined from the Tait parameters. The κT value at 0.1 MPa for nitromethane was smallest among these for aliphatic nitro-compounds. There was no difference between the values of κT at 0.1 MPa for nitroethane and 1-nitropropane.

(Liquid + liquid) equilibria of (water + ethanol + a C8 alkanol) from 0.1 to 200 MPa at 298.15 K

Tie lines for {water + ethanol + (octan-1-ol or octan-2-ol or 2-ethylhexan-1-ol)} have been measured in the range 0.1 to 200 MPa at 298.15 K. The immiscibility region depends on structural differences of the alkanols, reducing in order of 2-ethylhexan-1-ol, octan-2-ol, and octan-1-ol. Effects of pressure on the binodal curves and on the tie lines have been observed in the same way as for the mixtures previously studied. From the viewpoint of the distribution coefficient D2 of ethanol and separation factor α, it was found that 2-ethylhexan-1-ol is the most suitable for extracting ethanol among the three alkanols. Any of the alkanols has high efficiency for separation in the region in which the capacity of alkanol to extract ethanol is small. Elevation of pressure results in a lowering of the ability of the alkanols as extractants.

Effect of Water on Hydrolytic Cleavage of Non-Terminal α-Glycosidic Bonds in Cyclodextrins To Generate Monosaccharides and Their Derivatives in a Dimethyl Sulfoxide–Water Mixture

Hydrolytic cleavage of the non-terminal α-1,4-glycosidic bonds in α-, β-, and γ-cyclodextrins and the anomeric-terminal one in d-maltose was investigated to examine how the cleavage rate for α-, β-, and γ-cyclodextrins is slower than that for d-maltose. Effects of water and temperature were studied by applying in situ (13)C NMR spectroscopy and using a dimethyl sulfoxide (DMSO)-water mixture over a wide range of water mole fraction, xw = 0.004-1, at temperatures of 120-180 °C. The cleavage rate constant for the non-anomeric glycosidic bond was smaller by a factor of 6-10 than that of the anomeric-terminal one. The glycosidic-bond cleavage is significantly accelerated through the keto-enol tautomerization of the anomeric-terminal d-glucose unit into the d-fructose one. The smaller the size of the cyclodextrin, the easier the bond cleavage due to the ring strain. The remarkable enhancement in the cleavage rate with decreasing water content was observed for the cyclodextrins and d-maltose as well as d-cellobiose. This shows the important effect of the solitary water whose hydrogen bonding to other water molecules is prohibited by the presence of the organic dipolar aprotic solvent, DMSO, and which has more naked partial charges and higher reactivity. A high 5-hydroxymethyl-2-furaldehyde (5-HMF) yield of 64% was attained in a non-catalytic conversion by tuning the water content to xw = 0.30, at which the undesired polymerization by-paths can be most effectively suppressed. This study provides a step toward designing a new optimal, earth-benign generation process of 5-HMF starting from biomass.