Self-assembled proline-amino thioureas as efficient organocatalysts for the asymmetric Michael addition of aldehydes to nitroolefins

A small co-catalyst library of amino thioureas has been established from chiral 1,3-diamines. These bifunctional thioureas can form assemblies with proline to cooperatively catalyze the asymmetric Michael addition of aldehydes to nitroolefins. Both the reaction rate (up to 98% yield for 18 h) and the enantioselectivity (up to 94% ee) were significantly improved upon in less polar solvents.     

Particle emission in the hydrodynamical description of relativistic nuclear collisions

The usual particle emission scenario used in hydrodynamics presupposes that particles instantaneously stop interacting once they reach some three dimensional surface. Here we set up a new formalism to study continuous particle emission during the whole expansion of thermalized matter. This scenario changes completely the usual interpretation of transverse momentum spectra, may help to understand data on strange particle ratios and is possible to include in hydrodynamical codes.     

Measurement of two-dimensional distribution profile of lead in a flame by planar laser-induced fluorescence spectroscopy

Abstract  

Producing refuse-derived fuel (RDF) is one of the most effective measures of refuse treatment. However, RDF often consists of high level of lead. To reduce lead emission during combustion, understanding of lead behaviors in flames is required. In this study, we have applied planar laser-induced fluorescence spectroscopy to detect lead not only in a non-luminous methane–air flame, but also in a luminous RDF flame. In a methane–air flame, the number density of Pb atoms does not depend on the flame temperature, but also on the combustion environments. In RDF flames, because of acceleration of oxidizing process of Pb, Pb fluorescence profile obtained at 25% O₂ became weaker than that at 20% O₂.     

Chemical modification of butyl rubber. I. Synthesis and properties of poly(ethylene oxide)-grafted butyl rubber

A new amphiphilic polymer, i.e., poly(ethylene oxide) (PEO)-grafted butyl rubber (IIR-g-PEO), was synthesized by chemical modification of chlorinated butyl rubber (CIIR). This synthesis was based on the reaction between chlorine in CIIR and potassium salt of polyethylene glycol monomethyl ether (PEGM). PEGM's with molecular weights of 750 and 2000 were used. The maximum grafting percent of the resulted copolymers after the purification was ca. 45%, regardless of the molecular weight of PEGM. The microphase separated structure was observed in the films of IIR-g-PEOs. IIR-g-PEO, whose PEO molecular weight was 2000 and whose PEO content was 23.8 wt %, swelled 3.1% in water, and it was six times larger than the swelling of CIIR. The hydrophilicity of grafted polymers depended on the molecular weight of PEO side chains and PEO content. Even when the PEO contents were same in the polymers which were grafted PEGM-750 and PEGM-2000, their swellings in organic solvents were not equal. It was due to the difference of the microphase-separated structures of the grafted polymers. IIR-g-PEO, whose PEO molecular weight was 750 and whose PEO content was 10.3 wt %, swelled 1.5% in water, but showed an excellent emulsifying ability, where an oil-in-water-type emulsion was formed. © 1993 John Wiley & Sons, Inc.     

Dielectric relaxation and ionic transport in poly(ethylene carbonate)‐based electrolytes

To study the ion‐conductive and dielectric properties of polymer electrolytes based on poly(ethylene carbonate) (PEC) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the complex permittivity and conductivity were measured using broadband dielectric spectroscopy. The temperature dependence of the relaxation frequency and ionic conductivity for PEC‐LiTFSI electrolytes (1 – 200 mol%) indicates that the segmental motion of PEC chains decreases with the addition of just 1 mol% of Li salt and increases with increasing concentration above 10 mol%. According to the Walden rule for PEC‐based electrolytes, the value of deviation from the reference line increased, and the fragility and decoupling exponents decreased with increasing salt concentration. These results indicate that there are large numbers of ion pairs and aggregated ions, which imply low ionicity and reduced fragility in highly concentrated PEC‐based electrolytes. Copyright © 2016 John Wiley & Sons, Ltd.     

Strain-Induced Ring Expansion Reactions of Calix[3]pyrrole-Related Macrocycles

The recent discovery of calix[3]pyrrole, a porphyrinogen-like tripyrrolic macrocycle, has provided an unprecedented strain-induced ring expansion reaction into calix[6]pyrrole. Here, we synthesized calix[n]furan[3-n]pyrrole (n=1∼3) macrocycles to investigate the reaction scope and mechanism of the ring expansion. Single crystal X-ray analysis and theoretical calculations revealed that macrocyclic ring strain increases as the number of inner NH sites increases. While calix[1]furan[2]pyrrole exhibited almost quantitative conversion into calix[2]furan[4]pyrrole within 5 minutes, less-strained calix[2]furan[1]pyrrole and calix[3]furan were inert. However, N-methylation of calix[2]furan[1]pyrrole induced a ring-expansion reaction that enabled the isolation of a linear reaction intermediate. The mechanism analysis revealed that the ring expansion consists of regioselective ring cleavage and subsequent cyclodimerization. This reaction was further utilized for synthesis of calix[6]-type macrocycles.     

Excited-State Aromaticity of Gold(III) Hexaphyrins and Metalation Effect Investigated by Time-Resolved Electronic and Vibrational Spectroscopy

Expanded porphyrins with appropriate metalation provide an excellent opportunity to study excited-state aromaticity. The coordinated metal allows the excited-state aromaticity in the triplet state to be detected through the heavy-atom effect, but other metalation effects on the excited-state aromaticity were ambiguous. Herein, the excited-state aromaticity of gold(III) hexaphyrins through the relaxation dynamics was revealed via electronic and vibrational spectroscopy. The S_Q states of gold [26]- and [28]-hexaphyrins showed interconvertible absorption and IR spectra with those of counterparts in the ground-state, indicating aromaticity reversal. Furthermore, while the T₁ states of gold [28]-hexaphyrins also exhibited reversed aromaticity according to Baird's rule, the ligand-to-metal charge-transfer state of gold [26]-hexaphyrins contributed by the gold metal showed non-aromatic features arising from the odd-number of π-electrons.     

Thermal analysis of cesium hafnium chloride using DSC–TG under vacuum,nitrogen atmosphere,and in enclosed system

Journal of Thermal Analysis and Calorimetry - This paper reports on the preparation of undoped cesium hafnium chloride (Cs2HfCl6) and study of its thermal properties. The Cs2HfCl6 is considered,...