Regioselective hydroxylation of the xylyl linker in a diiron(III) complex having a carboxylate-rich ligand with H2O2

Reaction of a diiron(III) complex having a xylta4- ligand (N,N,N',N'-m-xylylenediamine tetraacetate) with H2O2 resulted in regioselective hydroxylation of the m-xylyl linker. The reaction mimics the self-hydroxylation of a phenylalanine side chain found for ribonucleotide reductase (R2-W48F/D84E).     

Development of a portableα-particle counter for public acceptance activities

There is currently great interest in iodine as a micro nutrient. Both high and low intakes have been associated with thyroid cancer incidence. Development of dietary iodine monitors is needed to supplement the use of dietary recall methods which have not been well validated for iodine. In this study, 30 pooled urine samples, from ethnic groups on various islands in the South Pacific, were analyzed for iodine using epithermal instrumental neutron activation analysis (EINAA).University of Mo Chemistry Department, Columbia, MO 65211     

Negative magnetoresistance and nonlinear conduction in Ti0.99V0.01Se2

Both magnetic and electric field dependences of transport coefficients are investigated on the layered material Ti_1-xV_xSe₂ (x = 0.01). In contrast to semimetallic TiSe₂, the resistivity of the V-doped samples increases with decrease of temperature even in the low temperature region. At liquid helium temperatures it is found that the resistivity is strongly dependent on electric field strength. The behaviour of the nonlinear conduction is similar to that observed in 1T-TaS₂. In the low field (Ohmic) region anomalously large negative mangetoresistance is observed, Δ?/?₀ = -80% at 1.6 K and 60 KOe. Moreover the Hall coefficient is also found to depend on both magnetic and electric fields. All the experimental data suggests that mobile carriers are excited by the applied fields.     

Allylation of phenoxides by crown ethers and their polymers

Allylation of sodium phenoxide in the presence of crown ethers produces a high ratio of O/O + C allylation when conducted in water, phenol, benzene, or diethyl ether. The striking increase in the product ratios is attributed to specific complexation of the crown ethers that facilitate the dissociation of the ion pair aggregate of the sodioderivative in benzene or diethyl ether. The crown ethers may act as a phase transfer catalyst when the reaction is run in water. Furthermore, the O/O + C ratios of the allylation strongly depend on the kind of crown ethers used. To examine their effect the allylation of sodium phenoxide was studied with various crown ethers, such as 18-crown-6, benzo-18-crown-6, benzo-15-crown-5, poly(vinylmonobenzo-15-crown-5), and poly(vinylmono-benzo-18-crown-6), as catalysts. It was found that among these crown ethers poly(vinylmono-benzo-15-crown-5) was the most effective catalyst.     

Anomalous effect of nitrogen on side-chain alkylation of toluene with methanol over solid bases

The alkylation of toluene with methanol was carried out at 500°C over various base catalysts. The activity of MgO was found to be highest when treated specially with nitrogen. The effect of nitrogen was anomalously large, 8, 8% ethylbenzene and 2.3% styrene being formed.

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500°C . MgO, . : 8,8% 2,3% .

     

New crystalline polymers: poly(2,5‐dialkyl‐1,4‐phenylene oxide)s

New heat‐reversibly crystalline poly‐(alkylated phenylene oxide)s are described. the oxidative polymerization of 2,5‐dimethylphenol catalyzed by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane) copper dichloride produced poly(2,5‐dimethyl‐1,4‐phenylene oxide), which showed heat‐reversible crystallinity with a high melting point at ca. 300°C, although the isomeric polymer, poly(2,6‐dimethyl‐1,4‐phenylene oxide), never recrystallizes once melted. The polymerization of 2,5‐diethylphenol and 2,5‐dipropylphenol gave the polymers consisting of 1,4‐phenylene oxide units; the latter polymer possessed heat‐reversible crystallinity, however, the former one did not.     

Laboratory experiments on vortices colliding with multiple islands

Laboratory experiments have been performed to investigate the physical processes that govern the interaction of a self-propagating barotropic cyclonic vortex with aligned circular cylinders. The motivation was to understand the dynamics which controls the interaction of North Brazil Current (NBC) rings with the Lesser Antilles (LA) in the Eastern Caribbean Sea. The geometrical parameter regulating the flow in the experiments was the ratio of the gap size to the diameter of the incident vortex, G /d. The range 0.03 ≤ G /d ≤ 0.4 was studied. Since the passages of the LA have values of 0.07 ≤ G /d ≤ 0.3 [2], the experimental results might explain recent oceanic observations [3]. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of C-nucleosides via coupling of ribosyl fluoride with typical aromatic heterocycles bearing a TMS group

The direct coupling reaction of D -ribosyl fluoride with typical π-excessive aromatic heterocycles such as furan, thiophene, pyrrole, benzofuran, benzothiophene, and indole and their trimethylsilyl derivatives was performed in the presence of boron trifluoride to afford the corresponding C-nucleosides in moderate to good yields.