Measurements of Ir concentration in geological standard samples using neutron activation analysis with multiple gamma-ray coincidence method

In this study, the Ir concentrations in some standard rock samples were determined by using the multiple γ-ray detection method. The use of the multiple γ-ray detection method, which was developed for nuclide quantification, yielded better resolution and sensitivity than the ordinary singles γ-ray detection method. Iridium is one of the least abundant elements in Earth’s crust, with an average mass fraction of 0.001 ppm in a crust rock. However, iridium is relatively more abundant (concentration: 0.5 ppm or more) in undifferentiated meteorites. Therefore iridium abundance anomalies in geological samples provide important information about meteorite impact. The standard rock samples used in this study were SARM-76, FC-1 and FC-2. The SARM-76 was prepared from a platinum ore, and issued by the south African bureau of standards. FC-1 and FC-2 were obtained from fish clay sediment samples from Stevens Klint, Denmark.     

Transfer of Technetium from Paddy Soil to Rice Seedling

Tracer experiments on the chemical transformation of technetium in paddy soil and the transfer to rice seedlings have been carried out using ^95mTc as a tracer. Two common Japanese soils, Andosol and Gray lowland soil were used in the soil incubation experiments. The chemical form of soluble Tc in soil water was a mixture of Tc-organic matter complex, Tc-iron complex and pertechnetate. An uptake experiment with rice seedlings using nutrient solution showed that the Tc-organic matter complex was less available than pertechnetate or the Tc-iron complex. These chemical forms of Tc were also observed in the root bleeding sap of rice seedlings when introduced to the nutrient solution containing soluble Tc. These results suggested that the transfer of technetium from soil to rice would depend on the chemical form of Tc and they would transport from the root to the leaf without chemical transformation.     

Solvent effects on extraction of alkali metal picrates with 15-crown-5 into various organic solvents. Elucidation of fundamental equilibria which govern extraction-efficiency and -selectivity

Extractions of alkali metal (Na-Cs) picrates (MA) with 15-crown-5 (15C5) into various diluents of low dielectric constant were conducted at 25 degrees C. Using the extraction data, the ion-pair formation constants (K(MLA)) in water of 15C5-MA 1:1:1 complexes were determined by an equation derived from the regular solution theory (logK(MLA)=4.43+/-0.27 for Na, 3.27+/-0.42 for K, 3.58+/-0.35 for Rb, and 2.78+/-0.41 for Cs). The actual overall extraction equilibrium constants were obtained by considering the concentrations of the 1:1:1 15C5 complexes and the ion-pair formation between uncomplexed alkali metal and picrate ions in the aqueous phase. The distribution constants of the 15C5 complexes were calculated and their partition behavior is explained by the regular solution theory. Molar volumes and solubility parameters of 15C5 itself and the complexes were determined. Extraction-efficiency and -selectivity of 15C5 for alkali metal picrates were completely elucidated from the standpoint of equilibrium.     

Analysis of the Pore Structure of Ion-Exchange Resins and the Adsorption Equilibrium of Fe3+/Cl− Complex Ions

The microstructure of ion-exchange resins has been investigated to understand more clearly the ion-exchange mechanism. Nine types of resins with different pore structures were used: all of the polystyrene family crosslinked with divinylbenzene and anionic resins, with mesh sizes ranging from 100 to 200, except for one (20–50 mesh). Various pore volumes of each resin were determined by measurements of intrusion of some chemical species (H₂O, Nd³⁺, and Hg) into the resin. The results are analyzed on the basis that an ion-exchange resin particle consists of four regions. They are: 1) the mercury intrusion region, 2) the region where coions (such as Nd³⁺) can intrude but mercury cannot, 3) the region where water or counterions can intrude but coions cannot, and 4) the polymer matrix region occupied by the polymer skeleton. The former two regions are not influenced by the resin-fixed ionic groups. While it used to be thought that specific adsorption of counterions may occur in the entire exchange resin particle, it is appropriate to consider that specific adsorption takes place only in the latter two regions. According to this point of view, the adsorption equilibrium of the Fe³⁺/Cl^? complex ions could be explained more satisfactorily.     

The substituent effect on mesomorphic properties of 4-octyloxyphenyl 4-(4-R-3-nitrobenzoyloxy)benzoates and 4-(4-octyloxybenzoyloxy)phenyl 4-R-3-nitrobenzoates

Abstract

The thermal properties of 4-octyloxyphenyl 4-(4-R-3-nitrobenzoyloxy) benzo-ates (1) and 4-(4-octyloxybenzoyloxy)phenyl 4-R-3-nitrobenzoates (2) have been examined, where R = hydrogen, halogens, alkyl and alkoxy groups. The derivatives of compound 1 incorporating hydrogen, halogens, methoxy and nitro groups show a smectic A phase having a bilayer arrangement, and the others with a long alkoxy group show the S_A phase with the monolayer arrangement. The derivatives of compound 2 incorporating halogens, and the nitro group show the S_A phase with the monolayer arrangement. The alkoxy derivatives show a smectic C phase as well as the nematic phase. The nitro group at the lateral position tends to increase the ratio of the S_A-N transition temperature to the N-I. The effect of the nitro group on the smectic properties has been discussed in terms of the structural and electrostatic nature of the nitro group.     

Monolayer-protected Au cluster (MPC)-supported Ti-BINOLate complex

[reaction: see text] Disulfides bearing (R)-1,1'-bi-2-naphthol ((R)-BINOL) moieties at each terminal position have been successfully introduced on the surface of Au cluster. Ti-BINOLate complex generated from the obtained monolayer-protected Au cluster (MPC) promoted catalytic asymmetric alkylation of benzaldehyde with Et(2)Zn to afford the adduct in up to 98% yield with 86% ee. After completion of the reaction, the BINOL-functionalized MPC was easily recovered.     

Determination of micelle mass by electrospray ionization mass spectrometry

By electrospray ionization (ESI) mass spectrometry, micelle solutions of sodium cholate were investigated in detail in the presence and absence of ethanol. The average aggregation number could be evaluated from the spectra acquired under conditions where soft collisions adequate to measure the micelle solution were induced, and the value agreed well with that obtained previously by other methods. From the dependence on ethanol content, it was also found that the average aggregation number in aqueous solution without organic solvent could be reliably estimated. The ESI method proved to be a useful tool for determining the micelle mass in the original aqueous phase.     

Synthesis of 28,29-bisnor-(±)-kijanolide

0(26)-Methyl-28,29-bisnor-(±)-kijanolide (23) has been synthesized via aldol reaction of spirotetronate 3 with octahydronaphthalene aldehyde 4 and subsequent macrocyclization of the resulting product.     

Mechanism of the formation of a dehydrated ion by an unusual loss of oxygen at the 4'-carbonyl group of abscisic acid methyl ester in electron ionization mass spectrometry

Methyl ester of abscisic acid (ABA), a plant hormone, gives a dehydrated ion at m/z 260 in electron ionization mass spectrometry (EI-MS). This dehydrated ion had been considered to be derived only from the elimination of the tertiary hydroxyl group at C-1'. We found that 34% of the dehydrated ion was formed by elimination of the oxygen atom at the 4'-carbonyl group, and the remaining 66% by elimination of the 1'-hydroxyl group. This unusual elimination of the carbonyl oxygen was shown with [4'-(18)O]ABA methyl ester. Involvement of the 4'-carbonyl oxygen in dehydration was observed in methyl ester of phaseic acid (PA), a natural metabolite of ABA, but not in 1'-deoxy-ABA methyl ester or isophorone. This suggested that the 1'-hydroxyl group was necessary for the elimination of the 4'-carbonyl oxygen. ABA methyl esters labeled with stable isotopes showed that hydrogen atoms at the 1'-hydroxyl group and at C-4 or -5 or -3' or - 5' or -7' were eliminated with the 4'-carbonyl oxygen. These results allow us to propose a formation mechanism of the dehydrated ion derived from the elimination of 4'-carbonyl oxygen and hydrogen atoms at C-4 and 1'-oxygen in ABA methyl ester as follows: first, ionization at the 1'-hydroxyl group occurs to give an ion radical, and the proton at the 1'-oxygen migrates to the 4'-carbonyl oxygen after the bond fission between C-1'-C-6'; second, migration of the proton at C-4 to the 1'-oxygen is followed by migration of the protons at C-5 and C-7' to C-4 and C-5, respectively; finally, the proton at the 1'-oxygen migrates to the 4'-hydroxyl group, and H(2)O at C-4' is eliminated to give the dehydrated ion. Our findings point out that a dehydrated ion is not always derived from the elimination of a hydroxyl group.     

A Convenient Synthesis of 2, 3 - DI- O - Acetyl-1, 6 - Anhydro- β - D – Glucopyranose

Abstract

1, 2, 3-Tri-O-acetyl-6-O-benzyl-4-O-chloroacetyl-α- and -β-D-glucopyranose (4α β)were derived from 1, 2, 3-tri-O-acetyl-4, 6- O -benzyl-idehe-β-D-giucopyranose (1) in two steps. Compound 1, 1, 2, 3-tri-O -acetyl-β-D-glucopyranose (2), and 4α,β were subjected to the cyclization reaction using Lewis acids ( SnCl₄ and BF₃-etherate), to give corresponding 1, 6-anhydro derivatives.