Important Roles of Water Clusters Confined in a Nanospace as Revealed by a Synchrotron X-ray Diffraction Study.

States of water molecules confined in a nanospace designed by montmorillonite (negatively charged silicate layer) and charge compensating benzylammonium were investigated. Caffeine was used as a probe because of its compatibility for the fine structure of the interlayer water. Powder synchrotron radiation X-ray diffraction (SXRD) and adsorption isotherms of the water vapor revealed a metastable structure of bimolecular water layers (2WLs) in the interlayer space. Water molecules readily penetrated to expand the interlayer space to 0.56 nm. The interlayer space did not increase further even in the presence of excess water. According to the isosteric heat of water, the expansion was limited because of moderate hydration as forming 2WLs. Caffeine molecules replaced a part of the water molecules in the 2WLs to expand the interlayer space to 0.65 nm. Time-resolved SXRD with an accumulation time of 500 ms revealed that the interlayer expansion reached a steady state within a few minutes. The caffeine intercalation proceeded, involving a change in the molecular orientation that increased the contact area of the caffeine molecules. The interlayer expansion was limited in all the solvents examined (mixtures of water with methanol, ethanol, acetone, and tetrahydrofuran), while the packing density of the incorporated caffeine was maximized in the absence of an organic solvent. The water molecules confined in the interlayer space acted as an actuator to accommodate a large quantity of amphiphilic molecules by adapting the nanostructure, which was achieved by releasing the confined water molecules.

Catalyst- and Silane-Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover.

The catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal-catalyzed hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of nonconjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, N-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, the absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect on the solvent, thermal dependence, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for a radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

High iodine intake by preschool children in Miyagi prefecture, Japan.

OBJECTIVES: Standard Tables of Food Composition in Japan 2010 (FCT) remain incomplete for iodine contents. This survey was initiated to develop a method to cope with this shortage and to find daily iodine intake of preschool children in Japan. METHODS: Data were available for one-day food intake for 296 3- to 6-year-old children (the total cases). 128 samples (the selected cases) were analyzed by ICP-MS for iodine (the measured values). Iodine intake was also calculated using FCT assuming that iodine contents in missing items were zero (the calculated values). RESULTS: Measured and calculated values for the selected 125 cases (after exclusion of 3 extreme cases) gave geometric means (GM) of 117.6 and 101.8 µg/day. The measured/calculated ratio in GM, 117.6/101.8 = 1.155, was applied to the calculated values for total 296 cases to estimate iodine intake (the estimated values). GM for the estimated value was 175.2 µg/day and it was 8.93 µg/kg/day after adjustment for body weight for 296 children. There was no significant difference between boys and girls. DISCUSSION: The GM values for both the measured and estimated values (n = 125 pairs) were 117.6 µg/day. The agreement suggested that the factor employed, 1.155, was proper and adequate. Literature survey suggested that values on a body weight basis were comparable between the children and adults in Japan. The levels were higher than levels in east Asian countries. CONCLUSIONS: A correction method was developed for estimation of daily dietary iodine intake. The iodine intake level for preschoolers was comparable to levels for adult population.