Endgroup analysis of isolated poly(methyl methacrylate) from graft copolymers of wool

In order to elucidate the termination mechanism in the graft copolymerization of methyl methacrylate to unreduced and reduced wool fibers, graft copolymers were prepared by means of the LiBr–K₂S₂O₈ redox sytem without homopolymer or with K₂S₂O₈ only with homopolymer at 30°C. The graft polymers (PMMA) were isolated almost completely from the wool trunk by an HCI-digestion method, leaving a few amino acid residues on the end of the graft polymers. Dinitrophenylation of the isolated polymer was carried out by various methods. The spectral features were almost the same as for dinitrophenylated amino acids of the usual type such as valine, leucine, and methionine, with a maximum in ultraviolet light at 340–345 mμ. From colorimetric analysis of the number of dinitrophenylated amino acid endgroups and the measurement of the average molecular weight of the isolated polymers, the number of amino acid endgroups linked to the graft polymers was calculated to be about one and two per polymer chain in reduced and unreduced wool, respectively, independent of the reaction system, graft-on, and molecular weight of graft polymers. From these facts, it was suggested that the most of isolated polymers are the truly grafted polymers. Also, the termination reactions have been explained as follows. In the unreduced wool, the restriction of mobility of the radical end might be expected, for the confinement of growing chains in wool fibers. This would be favorable to termination by recombination rather than by the disproportionation, since the former has a lower activation energy than the latter. Thus, the formation of intra- or intermolecular crosslinks might be considered between polypeptide chains. On the other hand, in the reduced wool, the mobility of graft polymers might be considered to be greater than that of unreduced wool because of its open structure. Therefore, termination would be principally by disproportionation between graft polymer radicals.     

Comparisons of soil pretreatment methods for SF-ICP-MS determination of ultra-trace level plutonium in water soluble and exchangeable fractions

Journal of Radioanalytical and Nuclear Chemistry - In this study, we developed a method to evaluate the potentially bioavailable fraction of Pu in agricultural soils by determining their water...     

Transport,thermal, and magnetic properties in heavy-fermion superconductor Ce2CoIn8

We have grown high purity single crystals of Ce₂CoIn₈ using the self-flux technique, and have investigated its transport, thermal, and magnetic properties, including the anisotropic features. Single crystals of Ce₂CoIn₈ were grown in the lower temperature region to avoid the formation of un-wanted phases such as CeCoIn₅ and CeIn₃ impurities. The results of the structural and physical measurements imply that the present single crystals have high purity. The electrical resistivity and specific heat measurements demonstrate that Ce₂CoIn₈ has a superconducting ground state with a distinct non-Fermi liquid character. This indicates that the superconductivity in Ce₂CoIn₈ arises out of the verge of the underlying quantum critical instability mediated by the antiferromagnetic correlations. Additionally, we investigate the crystalline electric field (CEF) energy scheme based on the temperature dependence of the specific heat and the anisotropic features in the susceptibility. We propose one of the CEF level schemes calculated on the basis of the CEF model that the first and second CEF states are located at Δ₁ = 82 K and Δ₂ = 102 K above the ground state doublet, respectively.     

Reaction of α,β‐unsaturated ketones with cerium(IV) salts in alcohol

Reaction of α,β‐unsaturated ketones with cerium(IV) salts or lanthanide triflates in alcohols gave good yields of the corresponding β‐alkoxy compounds. In the case of 2‐cyclopentenone and 2‐cyclohexenone, the 1,1,3‐trialkoxy acetal derivatives were obtained preferentially accompanied by β‐alkoxyketone, except 2‐cycloheptenone. However, in the reaction of 2‐cycloheptenone with alcohol using cerium(IV) sulfate (CS)‐molecular sieve, 1,1,3‐trialkoxy derivatives were obtained. Also, in the cases of 1‐penten‐3‐one, 4‐hexen‐3‐one and 3‐hepten‐2‐one, 1,1,3‐trialkoxy derivatives were obtained preferentially. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of sphingomyelin difluoromethylene analogue

As a new sphingomyelinase inhibitor, a novel sphingomyelin CF₂ analogue was designed and synthesized. One key step of this synthesis is the very mild hydrolysis of the oxazolidinone ring, a suitable intermediate for the introduction of a diethyl difluoromethylphosphonate group, by utilizing the characteristic electron withdrawing nature of the nosyl group at the oxazolidinone ring in an alcoholic solvent to produce the corresponding carbonate attaching at the secondary hydroxy group. The synthesized CF₂ analogue inactivated toward B. cereus sphingomyelinase with nearly the same attitude as the nitrogen analogue that we previously reported.     

Polymorphism-dependent fluorescence of 9,10-bis(pentafluorobenzoyloxy)anthracene

Anthracene derivatives possessing pentafluorobenzoyloxy moieties at 9- and 10-positions showed polymorphism affording two types of fluorescent crystals with blue and bluish green fluorescence in their crystalline state, respectively. Their single crystal X-ray structures showed that the degree of overlap of anthracene moieties was responsible for the difference in fluorescence. Fluorescence in the crystalline state originated in the dimer emission deduced from their excitation spectra.     

Dehydrative Allylation between Aldehydes and Allylic Alcohols through Synergistic N-Heterocyclic Carbene/Palladium Catalysis

Dehydrative allylation between widely available aldehydes and allylic alcohols to afford β,γ-unsaturated ketones was enabled by a synergistic merger of a thiazolium N-heterocyclic carbene catalyst and a palladium-bisphosphine catalyst.