Intermittent simulated moving bed chromatography: 3. Separation of Tröger's base enantiomers under nonlinear conditions

One of the modified simulated moving bed (SMB) processes, the intermittent SMB (I-SMB) process, has been recently analyzed theoretically [1] and its superior performance compared to the conventional SMB process has been demonstrated at a rather low total feed concentration through experiments and simulations [2]. This work shows that the I-SMB process outperforms the conventional SMB process also at high feed concentration where the species are clearly subject to a nonlinear adsorption isotherm. In the case of the separation of the Tröger's base's enantiomers in ethanol on ChiralPak AD, the two processes operated in a six-column 1-2-2-1 configuration (one column in sections 1 and 4 and two columns in sections 2 and 3) and in a four-column 1-1-1-1 configuration (one column in each section) are compared at high feed concentration through both experiments and simulations. Even under nonlinear conditions the four column I-SMB process can successfully separate the two enantiomers achieving purity levels as high as the two six column processes and exhibiting better productivity.     

3‐[4′‐(Diethylboryl)phenyl]pyridine: Exclusive Crystallization of the Cyclic Tetramer

The crystallization of 3‐[4′‐(diethylboryl)phenyl]pyridine ( 1 ), which formed a mixture of oligomers in solution with the cyclic trimer as a major component, in acetone at 0 °C afforded a cyclic tetramer that co‐crystallized with solvent molecules. Similarly, solutions of compound 1 in toluene at 10 °C and in benzene at 8 °C furnished the cyclic tetramer with the incorporation of toluene and benzene molecules, respectively, thus suggesting that the cyclic tetramer was the minor component. ¹³C CP/MAS NMR spectroscopy of precipitates of compound 1 suggested that precipitation from acetone and toluene each afforded mixtures of the cyclic trimer and the cyclic tetramer, whereas precipitation from benzene exclusively furnished the cyclic tetramer. Therefore, it appeared that crystallization readily shifted the equilibrium towards the cyclic tetramer in benzene. The thermodynamic parameters for the equilibrium between these two oligomers in [D₆]benzene, as determined from a van′t Hoff plot, were ΔH°=?8.8 kcal mol^?1 and ΔS°=?23.7 cal mol^?1 K^?1, which were coincident with previously reported calculations and observations.     

The dynamic birefringence of high polymers

The simultaneous measurement of the birefringence and strain of a sample subjected to sinusoidal strain is proposed as a means for elucidating the molecular mechanism of the response to high polymers to mechanical deformation. A linear phenomenologicical theory is proposed in which strain-optical coefficient distribution functions are assigned to the elastic and viscous members of a distribution of Maxwell elements. An apparatus has been constructed to determine the dynamic strain-optical coefficient at frequencies between 0 and 600 cycles/sec. By means of mechanical excitation of vibration at low frequencies and electromagnetic at high frequencies. The dynamic birefringences of polyethylene has been studied at room temperature over this frequency range.     

Preparation of macroreticular-type oleophilic anion exchange resin membrane and its permselectivity to halides and thiocyanate

Macroreticular-type oleophilic anion exchange resin membranes containing high-molecular-weight ammonium ions such as tri-n-octylbenzylammonium and tri-n-dodecylbenzylammonium as fixed site were freshly prepared. These membranes were wetted well with water-immiscible organic solvents even in aqueous surroundings. The properties of the membrane, i.e. porosity, water and organic solvent content, capacity and conductivity were determined. The permselectivity of the membrane impregnated with nitrobenzene or o-nitrophenyloctylether to halide and thiocyanate ions was evaluated by measurement of bi-ionic membrane potential and electrodialysis. p]The sequence of the permselectivity was Cl^? < Br^? < I^? < SCN^?, and was consistent with the Hofmeister anion series. The value of the permselectivity was 10–100 times larger than that of usual hydrophilic anion exchange membranes. It was found that the permselectivity of the present membrane was strongly dependent on the separation factor, which was in turn affected by the hydrophobicity of the membrane. The effect of the ion association between fixed ion-exchange site and counter ion on the specific conductance of the membrane was also discussed.     

Iitaka's fibrations via multiplier ideals

We give a new characterization of Iitaka's fibration of algebraic varieties associated to line bundles. Introducing an ``intersection number' of line bundles and curves by using the notion of multiplier ideal sheaves, Iitaka's fibration can be regarded as a ``numerically trivial fibration' in terms of this intersection theory.

     

Thermal decomposition of chromium oxide hydroxide: I. Effect of particle size and atmosphere

The thermal decomposition process of α-HCrO₂ and β-HCrO₂ having various crystal habits and sizes was studied in an atmosphere of H₂O, O₂, and air by means of thermal gravimetry, high temperature X-ray diffraction analysis, and electrical conductivity measurement. In H₂O vapor both α-HCrO₂ and β-HCrO₂ were decomposed directly into crystalline Cr₂O₃ through the reaction 2HCrO₂ → Cr₂O₃ + H₂O. In the presence of O₂, however, the decomposition temperature was lower than that in H₂O vapor and a two-stepped thermal decomposition spectrum (two peaks) was obtained. Two steps were clearly separated on the β-HCrO₂ and assigned, respectvely, to the reactions $\text{2}\text{HCrO}{}_2\text{+}\text{1}\text{2}\text{O}{}_2\text{→ 2}\text{CrO}{}_2\text{+}\text{H}{}_2\text{O}$ and $\text{2}\text{CrO}{}_2\text{→}\text{Cr}{}_2\text{O}{}_3\text{+}\text{1}\text{2}\text{O}{}_2$. On the α-HCrO₂ samples the first reaction was newly found and followed by the second reaction at higher temperatures. The atoms in the crystal of α-HCrO₂ and β-HCrO₂ were found to start internal migration at about 200 and 250°C, respectively.     

Preparation of visible-light-responsive TiO2-xNx photocatalyst by a sol-gel method: analysis of the active center on TiO2 that reacts with NH3

Active reaction centers for ammonia on titanium oxyhydroxide were explored to direct the search for an efficient sol-gel method for the synthesis of a titanium oxynitride (TiO2-xNx) sample with an efficient responsiveness to the visible light constituting a main part of the solar spectrum. The results lead to the conclusion that the site giving IR bands at around 2195 cm(-1) for the adsorbed CO molecules at 300 K is a reactive site and behaves as Lewis acid site in the coordination environment of distorted five-coordinate Ti4+ ions. Ammonia molecules are adsorbed on such a site to form -NH2 and -OH species during the heat treatments at a temperature above 373 K, and they are ultimately incorporated into the TiO2 lattice as nitride through the dehydration at higher temperatures of up to 723 K, resulting in the formation of an anatase type of TiO2-xNx.     

Thermodynamic, structural, and dynamic properties of supercooled water confined in mesoporous MCM-41 studied with calorimetric, neutron diffraction, and neutron spin echo measurements

Thermodynamic, structural, and dynamic properties of heavy water (D(2)O) confined in mesoporous silica glass MCM-41 C10, C12, and C14 were investigated by differential scanning calorimetry, neutron diffraction, and neutron spin echo (NSE) measurements, respectively. The DSC data showed that no crystallization of D(2)O confined in C10 occurs in a temperature range between 298 and 180 K, and that crystalline ice is formed at 204 and 221 K for C12 and C14, respectively. For C10, the neutron radial distribution functions of confined D(2)O suggested a structural change in the supercooled state between 223 and 173 K. For C10 sample, it has been found that the tetrahedral-like water structure is partially enhanced in the central part of pores at 173 K. For all the samples, the intermediate scattering functions from the NSE measurements are fitted by the Kohlrausch-Williams-Watts stretched exponential function which implies that confined supercooled D(2)O exhibits a wide distribution of relaxation times. For C10, C12, and C14 samples, between 298 and 240 K, the relaxation times of supercooled D(2)O follow remarkably well the Vogel-Fulcher-Tamman equation; for C10 sample, below 240 K, the relaxation times of nonfreezing D(2)O show an Arrhenius type behavior. From the present experimental results on calorimetric, structural, and dynamic properties, it has been concluded that supercooled D(2)O confined in MCM-41 C10 experiences a transition from high-density to low-density hydrogen-bonded structure at around 229 K.