There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

基礎講座 電気泳動(Electrophoresis)

Sustainable solvents are a topic of growing interest in both the research community and the chemical industry due to a growing awareness of the impact of solvents on pollution, energy usage, and contributions to air quality and climate change. Solvent losses represent a major portion of organic pollution, and solvent removal represents a large proportion of process energy consumption. To counter these issues, a range of greener or more sustainable solvents have been proposed and developed over the past three decades. Much of the focus has been on the environmental credentials of the solvent itself, although how a substance is deployed is as important to sustainability as what it is made from. In this Review, we consider several aspects of the most prominent sustainable organic solvents in use today, ionic liquids, deep eutectic solvents, supercritical fluids, switchable solvents, liquid polymers, and renewable solvents. We examine not only the performance of each class of solvent within the context of the...

Green and Sustainable Solvents in Chemical Processes

Bull. Chem. Soc. Jpn. への投稿のすすめ

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Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques

The reaction rate of the hydrolysis of fluorescein diacetate (FDA) is several times larger in the frozen state than that in the unfrozen solution of the same composition at the same temperature. The freeze concentration of reactants in the liquid phase expelled form ice crystals cannot explain the kinetic enhancement of pseudo first order reactions such as the FDA hydrolysis. However, the reaction rate increases as the freeze concentration ratio becomes larger at a constant temperature. Direct pH measurements have revealed that the basicity of the liquid phase is unchanged at any concentration ratio, suggesting that the reactivity enhancement is not caused by increased basicity. The reaction rate enhancement is clearly related to the size of the space in which the liquid phase is confined upon freezing. The ice wall itself or the water structure formed near the wall should thus be responsible for this kinetic enhancement.

Enhanced kinetics of pseudo first-order hydrolysis in liquid phase coexistent with ice.

The local structures of Cl- and Br- in an anion-exchange resin have been investigated by X-ray absorption fine structure (XAFS). The resins, which have been equilibrated under various partial water vapor pressures to allow the anions to have various hydration numbers, are provided for XAFS measurements. The XAFS spectra indicate that two scattering groups around the counteranion are present, that is, water molecules and an ion-exchange group. Regression analyses allow the separation of the contributions from these two scattering groups; thus, the average hydration number (N) is determined. The hydration number linearly increases with increasing the number of water molecules (n) adsorbed by an ion-exchange pair (an ion-exchange group and a counteranion) until the ion-exchange pair adsorbs ca. 3 water molecules, indicating that all of the adsorbed water molecules coordinate the counteranion. However, an increase in N with increasing n becomes small as n exceeds 3; N finally reaches 3.9 (±0.4) for Cl- and ca...

Hydration of Halide Anions in Ion-Exchange Resin and Their Dissociation from Cationic Groups

When an aqueous electrolyte is frozen, anions and cations are distributed between liquid and ice phases in different fashions. This partition imbalance is relaxed by the transfer of H+ and OH– to each phase, resulting in the acidification of the liquid phase when the cation is better distributed in the ice phase than the anion and in the basification in the opposite situation. In this work, a pH change in the liquid phase has been precisely evaluated by fluorescence ratiometry with pyranine as the pH probe. For frozen alkali chlorides (LiCl, NaCl, and KCl), the liquid phase is always basified by freezing due to the preferential partition of Cl– over the alkali metal cations. Changes in pH are quantitatively analyzed by a partition model, in which the distribution of an ion between the liquid and ice phases is determined by the partition coefficient. Since the concentration of a salt (i.e., ions) in the liquid phase in contact with ice becomes higher as freezing proceeds, the concentration of the ions in t...

Imbalance between Anion and Cation Distribution at Ice Interface with Liquid Phase in Frozen Electrolyte As Evaluated by Fluorometric Measurements of pH

Solute diffusion coupled with an orthogonal laminar flow has been systematically studied with wide-bore capillaries to establish its limitations and reveal its potentials as separation methodology requiring neither chemical nor physical interactions. Simulations based on the advection-diffusion equation in a cylindrical coordinate system indicate several important features of this potentially useful method: (1) if a solute diffuses over the entire cross-section of the capillary before it is eluted from the capillary, it behaves as a diffusive solute and gives a Gaussian-shaped peak (diffusion peak) having an apex at the traveling time of the average flow; (2) when a solute is poorly (or not) diffusive, a new peak appears with an apex at the elution time of the maximum flow (non-diffusion peak); (3) these two peaks are simultaneously detected for intermediately diffusive solutes; (4) the transformation from the diffusion to non-diffusion peak occurs when the solute diffuses over the distance 0.86 times as large as the capillary radius before it leaves the capillary. These results of simulations are consistent with experimental results for selected solutes having various diffusivities. This method has proved useful particularly for the evaluation of diffusion coefficients of poorly diffusive solutes. Separation of PS particles having different sizes is also attempted.

Solute distribution coupled with laminar flow in wide-bore capillaries: what can be separated without chemical or physical fields?

The local structures of Br- in ion-exchange resins are studied with XAFS at the Br−K edge. Br--form anion-exchange resins having different ion-exchange groups, i.e., tertiary ammonium (R-3) and quaternary ammonium ion (R-4), are examined after being soaked in water, methanol (MeOH), and some polar aprotic solvents. The resins soaked in aprotic solvents give almost the same spectral features as dry resins, indicating that Br- is tightly bound by the ion-exchange sites. Br- is entrapped inside the tripod composed of three equivalent methyl groups of the ion-exchange group in the R-4 resin, while it strongly interacts with the ammonium hydrogen of the ion-exchange group of the R-3 resin. In the latter case, the scattering from methyl and methylene carbon atoms in the ion-exchange group also contributes to XAFS spectra. In contrast, characteristic features are confirmed when the resins are soaked in water and MeOH. Detailed analyses of XAFS spectra imply that two species, i.e., solvated Br- and that bound on ...

Makoto Harada

Papers

Enhanced kinetics of pseudo first-order hydrolysis in liquid phase coexistent with ice.

Hydration of Halide Anions in Ion-Exchange Resin and Their Dissociation from Cationic Groups

Imbalance between Anion and Cation Distribution at Ice Interface with Liquid Phase in Frozen Electrolyte As Evaluated by Fluorometric Measurements of pH

Solute distribution coupled with laminar flow in wide-bore capillaries: what can be separated without chemical or physical fields?

Solvation Structure of Bromide Ion in Anion-Exchange Resins