Takayoshi Kimura

Thermodynamics of liquid mixtures containing methyl methylthiomethyl sulfoxide. I: Excess volumes of (water or benzene or dimethyl sulfoxide + methyl methylthiomethyl sulfoxide) and (water or benzene + dimethyl sulfoxide) at 298.15 and 318.15 K

Abstract To compare the difference between the thermodynamic properties of binary mixtures containing methyl methylthiomethyl sulfoxide ( mmtso ), CH 3 (CH 3 SCH 2 )SO, and those containing dimethyl sulfoxide ( dmso ), excess molar volumes for the title mixtures have been determined by use of bicapillary pyknometers. The signs of excess volumes and their temperature coefficients for the mixtures containing mmtso are similar to those for the corresponding mixtures of dmso . The curve of excess molar volume for (water + dmso ) plotted against mole fraction x of dmso shows an inflection point in the range: x

Deuterium isotope effect on excess enthalpies of methanol or ethanol and their deuterium derivatives at 298.15 K

AbstractExcess enthalpies of six binary mixtures of CH3 OD+CH3 OH, CH3 OD+CD3 OD, CD3 OD+CH3 OH, C2 D5 OD+C2 H5 OH, C2 D5 OD+C2 H5 OD, C2 H5 OD+C2 H5 OH have been determined over the whole range of mole fractions at 298.15 K in order to know the isotopic effect on hydrogen-bonding accurately, although there are many reports on the differences in the strength of hydrogen-bonding between OH and OD.All excess enthalpies measured are very small and endothermic. The mixtures of CH3 OD+ CH3 OH, and C2 D5 OD+C2 H5 OH showed the largest excess enthalpies among each methanol and ethanol mixtures. The difference of intermolecular interaction between OH and OD in methanol and ethanol was almost same value of (1.82±0.04) J mol-1 Excess enthalpies of 1,4-dimethylbenzene+1,3-dimethylbenzene and 1,4-dimethylbenzene+1,2-methylbenzene were measured by three different principle calorimeters at 298.15 K in order to know the precision of calorimetry for a small enthalpy change.

Excess Enthalpies of Binary Mixtures of Propanediamine+Propanediol at 298.15 K

The molar excess enthalpies of 1,2- and 1,3-propanediamine+1,2- and 1,3-propanediol have been determined at 298.15 K by using a twin-microcalorimeter which requires each component liquid 1 to 1.5 cm3 for a series of runs over the whole range of mole fraction. All excess enthalpies are exothermic and large. An equilibrium constant K1 expressed in terms of mole fractions and standard enthalpy of formation of 1:1 complex have been evaluated by ideal mixtures of momomeric molecules and their associated complexes.

Some problems in solution microcalorimetry, experimental experiences by the authors, and the enthalpy-entropy compensation in cyclodextrin + alcohol inclusion-complex formation in aqueous solutions

Abstract A short summary of the milestones to the present stage of achievement by the authors, some problems encountered in their course of investigations, and their countermeasures are described. A precise experimental results of the excess enthalpy for (cyclohexane + n -hexane) at (298.15 ± 0.001) K are given as a reliability test of the microcalorimetry with small amounts of samples. A couple of enthalpy-entropy compensation rules in the formation equilibria of inclusion complexes between α- and β-cyclodextrins and some alcohols in water at 298.15 K are described, which have been found from their calorimetric determination of the enthalpies and entropies of inclusion after overcoming the problems.

Thermodynamics of liquid mixtures containing ethyl methylthiomethyl sulfoxide: V. Excess enthalpies of (deuterochloroform + methyl ethylthiomethyl sulfoxide), (deuterochloroform dimethyl sulfoxide) and (deuterochloroform + chlorof

Abstract The molar excess enthalpies HmE of the title mixtures have been determined by using a twin-microcalorimeter of the heat-conduction type which requires only 10 cm3 of each component liquid for a series of runs over the whole range of mole fractions. The HmE of CDCl3 + CHCl3 is nearly athermal and its maximum value is 9 J mol−1. The HEm of CDCl3(1) + CH3SOCH2,SCH3(2) and DMSO(2) are exothermic. The minimum values of HmE are −2.27 kJ mol−1 at x2 = 0.4 for the former mixture and −2.91 kJ mol−1 at x2 = 0.4 for the latter. An equilibrium constant K1 expressed in terms of mole fractions and standard enthalpy ΔH1XXX of formation of a 1:1 associated complex between CDCl3 and CH3SOCH2SCH3 have been evaluated to be K1 = 3.8 and ΔH1XXX (101325Pa) = −6.6 kJ mol−1, by assuming an ideal mixture of CDCl3, CH3SOCH2SCH3 and their 1:1 and 2:1 associated complexes. The enthalpic stabilization on hydrogen bonding between CDCl3 and CH3SOCH2SCH3 molecules is smaller than that between CHCl3 and CH3SOCH2SCH3 molecules by about 23%.

Excess enthalpies of diethylether, ethylpropylether dipropylether + methyl methylthiomethyl sulfoxide or + dimethyl sulfoxide at 298.15 K☆☆☆

Abstract Excess enthalpies of six binary mixtures between methyl methylthiomethyl sulfoxide (MMTSO) or dimethyl sulfoxide (DMSO) and one of the dialkylethers (diethylether, ethylpropylether or dipropylether) have been determined at 298.15 K. All the mixtures observed showed positive excess enthalpies over the whole range of mole fractions and miscibility gaps. The mutual solubilities decreased with the increase in size of the alkyl radicals. Excess enthalpies determined at saturated mole fractions also decreased with the increase in size of the alkyl radicals. The enthalpies and entropies of transfer between conjugate mixtures were determined. The excess enthalpies of the mixtures containing DMSO were larger than those containing MMTSO. A comparison of the results with those for six binary mixtures containing a cyclic ether is made.

Excess enthalpies of cycloether + methyl methylthiomethyl sulfoxide or dimethyl sulfoxide at 298.15 K

Excess enthalpies of ten binary mixtures of each of methyl methylthiomethyl sulfoxide (MMTSO) and dimethyl sulfoxide (DMSO) with one of the cycloethers (oxane, 1,3- and 1,4-dioxanes, oxolane and 1,3-dioxolane) have been determined at 298.15 K. All the mixtures show positive excess enthalpies over the whole composition range. Excess enthalpies of the cycloether + MMTSO or DMSO decrease with increasing number of oxygen atoms in the cycloether molecules, except for oxolane + MMTSO. Excess enthalpies of MMTSO + cycloethers are smaller than those of DMSO + cycloethers for the same cycloether except for the 1,3-dioxolane mixtures.ZusammenfassungBei 298.15 K wurden die Überschußenthalpien von zehn binären Gemischen aus jeweils Methylmethylthiomethylsulfoxid (MMTSO) bzw. Dimethylsulfoxid (DMSO) mit einem der cyclischen Ether (Oxan, 1,3- und 1,4-Dioxan, Oxolan und 1,3-Dioxolan) bestimmt. Alle Gemische zeigen im gesamten Konzentrationsbereich eine positive Überschußenthalpie. Die Überschußenthalpien von Cycloether + MMTSO oder DMSO sinken mit zunehmender Anzahl der Sauerstoffatome im cyclischen Ether, mit Ausnahme von Oxolan + MMTSO. Die Überschußenthalpien für MMTSO + Cycloether sind kleiner als die für DMSO + entsprechender Cycloether, eine Ausnahme bilden die Gemische mit 1,3-Dioxolan.

Determination of excess volumes of benzene +o-terphenyl at 288.15, 298.02, and 302.78 K

Abstract Densities of benzene + o-terphenyl have been measured as a function of composition at 288.15, 298.02, and 302.78 K by means of the pyknometric method. The density of the supercooled melt of o-terphenyl has also been measured from 288.15 to 313.19 K. The excess molar volumes and the excess partial molar volumes of the components are evaluated from the densities measured. The excess volumes are all negative at these temperatures, and they are more negative when the temperature is increased.

Excess enthalpies of some halogenized aromatic compounds + methyl methylthiomethyl sulfoxide or + dimethyl sulfoxide at 298.15 K XI. Thermodynamics of liquid mixtures containing methyl methylthiomethyl sulfoxide

Abstract Excess enthalpies of binary mixtures between each of chlorobenzene, fluorobenzene, bromobenzene, chlorotoluene and fluorotoluene and methyl methylthiomethyl sulfoxide (MMTSO) or dimethyl sulfoxide (DMSO) have been determined at 298.15 K. All mixtures showed positive enthalpy change over the whole range of mole fractions. Partial molar enthalpies of the mixtures containing MMTSO(2) around 0.95 in mole fraction have maxima and minima. Linear relations are obtained between limiting excess partial molar enthalpies and the square of the dipole moment except H 2 E,∞ of the mixtures containing fluorotoluene.

Mechanism for the inhibition of the acid degradation of ampicillin by 2-hydroxypropyl-β-cyclodextrin

The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution. In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry: the first-type had a high association constant K1 of 4.0-8.0·103 M-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K2 of 1.0·103 M-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in a two-step reaction and was characterized by a smaller K1:2of 4.0·102 M-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37°C. In weak acid and neutral solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl group was included (Mode II). AMPC was very stable in these solutions (t1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system.