Study of radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. X. Influence of H2O on the styrene–silica gel system

To elucidate the reaction mechanism of radiation-induced polymerization of the styrene—silica gel system, the influence of H₂O as adsorbed water and inhibitor of cationic polymerization was investigated by two methods. Monomer conversion decreased as H₂O increased. In general, percent grafting decreased as H₂O increased, but the presence of a small amount of H₂O increased the percent grafting. Grafting at 16 Mrad has a maximum value at a water content of about 0.2%. This seems to be due to two effects of H₂O: percent grafting increases due to restraint of cationic polymerization by H₂O, but the percent grafting decreases due to adsorption water which interrupts the contact of styrene with silica gel. In GPC spectra, the low molecular weight peaks of both graft polymers and homopolymers decreased when H₂O was added. The GPC results suggest that the number of positive holes which initiate cationic polymerization is very large.     

Photodegradation of polyethylene in the presence of ferric chloride

Effects of ferric chloride (FeCl₃) on photodegradation of high-density polyethylene (PE) were investigated by using ESR and infrared spectrometry. In the system with irradiation at light of λ > 220 nm, PE irradiated at 77°K yielded an 8-line spectrum, the intensity of which was markedly weakened by using FeCl₃ with the sample, indicating a distinct depression of radical formation. On the other hand, PE with the use of FeCl₃ yielded radicals under irradiation only with light of λ > 300 nm, showing a singlet spectrum with a line width of 15 gauss. For photooxidized PE, almost the same effect of FeCl₃ was observed. On irradiation at room temperature, PE samples with and without FeCl₃ showed a singlet spectrum with line widths of 15 and 25 gauss, respectively. On the other hand, the unsaturated double bond contained in a small amount in PE sample was observed by infrared study to be decreased with photoirradiation; however, the decrease was sharply depressed with the addition of FeCl₃ to the sample. The degradation of carbonyl group in a photooxidized sample was markedly affected by photoirradiation, and the decay was obviously reduced for the sample on addition of FeCl₃. It is concluded that FeCl₃ works upon photodegradation of PE to enhance the Norrish type II reaction and to accelerate the formation of unsaturated double bond in the chain.     

Reactivities of Stable Rotamers: XLIV. Ring-Opening Reactions of 1-(9-Fluorenyl)-2-(2-methyl-2-oxiranyl)naphthalene Rotamers With Acids and the Structure of Oxiranes

X-ray crystallography of the ap-form of the 1-(9-fluorenyl)-2-(2-methyl-2-oxiranyl)naphthalene has revealed that the carbon atom of the oxirane which is connected to the naphthyl group in this compound is almost planar. The specific structural features of the epoxy ring in this compound are caused by sterical effects and by the presence of a -system in the immediate vicinity of the oxirane ring. Certain differences have been found also in reactivity of rotational isomers of 2-X-substituted 1-[1-(9-fluorenyl)-2-naphthyl]ethyl cations (X = O, S, Se). At X = O arose more deprotonation product from the -position of the oxygen than in reactions of sulfur and selenium-containing analogs. Reactions of epoxides with zinc chloride almost exclusively gave the corresponding aldehydes.     

Mechanism of Macroscopic Motion of Oleate Helical Assemblies: Cooperative Deprotonation of Carboxyl Groups Triggered by Photoisomerization of Azobenzene Derivatives

Macroscopic and spatially ordered motions of self‐assemblies composed of oleic acid and a small amount of an azobenzene derivative, induced by azobenzene photoisomerization, was previously reported. However, the mechanism of the generation of submillimeter‐scale motions by the nanosized structural transition of azobenzene was not clarified. Herein, an underlying mechanism of the motions is proposed in which deprotonation of carboxyl groups in cooperation with azobenzene photoisomerization causes a morphological transition of the self‐assembly, which in turn results in macroscopic forceful dynamics. The photoinduced deprotonation was investigated by potentiometric pH titration and FTIR spectroscopy. The concept of hierarchical molecular interaction generating macroscale function is expected to promote the next stage of supramolecular chemistry.     

The First Catalytic Synthesis of an Acrylate from CO2 and an Alkene—A Rational Approach

For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C₁ building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we describe a homogeneous catalyst based on nickel that permits the catalytic synthesis of the industrially highly relevant acrylate sodium acrylate from CO₂, ethylene, and a base, as demonstrated, at this stage, by a turnover number of greater than 10 with respect to the metal.     

Upgrade of the nuclear resonant scattering beamline, BL09XU in SPring-8

An Upgrade of the nuclear resonant scattering beamline, BL09XU in SPring-8 has been conducted. A liquid nitrogen cooled high-heat load monochromator was installed and a 2nd experimental hutch was constructed. The instruments installed in the hutch allow for a variety of sample conditions. Newly developed high-resolution monochromators with better stability including the back scattering geometry monochromator have opened up the easy access to more isotopes and more precise measurements.     

A clothes‐peg‐shaped binuclear trans‐bis(2‐aminotroponato)palladium(II) complex bearing pentamethylene spacers

rac‐Bis{μ‐trans‐2,2′‐[pentane‐1,5‐diylbis(azanediyl)]ditroponato}dipalladium(II), [Pd₂(C₁₉H₂₀N₂O₂)₂], has been synthesized and fully characterized using single‐crystal X‐ray diffraction, ¹H NMR, FT–IR and mass spectroscopy. The trans coordination, vaulted structure and anti conformation have been unequivocally established from the X‐ray diffraction studies. This is the first example of a bis(aminotroponato)palladium complex. In the crystalline state, the molecule has twofold symmetry and each molecular unit undergoes intermolecular offset π‐stacking of the tropone rings to afford heterochiral interpenetrating dimers that are aligned in a lamellar manner with a herringbone packing motif.     

Time Courses and Time‐Resolved Spectra of Firefly Bioluminescence Initiated by Two Methods of ATP Injection and Photolysis of Caged ATP

The time‐dependent characteristics of firefly bioluminescence initiated by manual injection of adenosine triphosphate (ATP) into buffer solution containing luciferin (Ln), luciferase (Luc) and Mg²⁺ were measured with a resolution of 10 ms, and compared with those obtained by photolysis of caged ATP. The time course depends on pH; both rise and decay rates decrease when pH is lowered from 7.8 to 6.8. In contrast, the parameter λ in the kinetic formula related to diffusion of ATP is almost independent of pH. The pH dependence of the time course of bioluminescence can be explained by the same pH tendency as the rate of ATP binding at the active site of Luc. The time‐resolved spectra can be decomposed into two Gaussian components with maxima at 2.2 and 2.0 eV. At pH 7.8, the band at 2.2 eV is more intense than that at 2.0 eV for all three concentration conditions. At lower pH, the band at 2.2 eV becomes weaker than that at 2.0 eV. The intensity ratio of the 2.0 and 2.2 eV bands is constant for duration time of 600 s for both injection and photolysis experiments, and the above conclusions are unaffected by the concentration ratio [Ln]/[Luc].